Differential effects of CLDR and PDR brachytherapy on cell cycle progression in a syngeneic rat prostate tumour model

PURPOSE: The study consisted of two treatment arms comparing the effects of CLDR (continuous low dose rate) and PDR (pulsed dose rate) brachytherapy on cell cycle progression in a radioresistant rat prostate tumour model. MATERIALS AND METHODS: Interstitial PDR and CLDR brachytherapy (both 192-Ir, 0.75 Gy/h) were administered to Dunning prostate R3327-AT1 carcinomas transplanted subcutaneously into the thigh of Copenhagen rats. Increasing doses of up to 20 as well as up to 40 Gy were applied. Cell cycle distributions of the aneuploid tumour cell subpopulations were determined at 4 h (3 Gy), 24 h (18 Gy), 48 h (20 and 36 Gy), as well as during the subsequent redistribution period (20 and 40 Gy) at 72, 96, and 120 h. Tumours either implemented with an empty tubing system (n=5) or under undisturbed growth (n=5) served as controls. Three animals were irradiated per time point and exposure condition. At least two flow cytometrical analyses were carried out per animal. RESULTS: The aneuploid cells possessed a constant DNA-Index of 1.9+/-0.06. In contrast to sham-treated controls, the aneuploid cell fraction with G2/M DNA content was significantly increased (p<0.05) after initiation of both, CLDR and PDR brachytherapy. However, CLDR resulted in an earlier accumulation of tumour cells in G2/M (24 h: 28% CLDR vs. 19% PDR, p<0.05) with a concomitant reduction of cells in G1, whereas PDR yielded delayed, but then more pronounced cell cycle changes, particularly expressed during the redistribution period after both 20 and 40 Gy. CONCLUSION: CLDR and PDR brachytherapy showed differential effects on cell cycle progression. The induction of a significantly earlier but also less persistent G2/M cell cycle arrest after CLDR compared to PDR brachytherapy implies that a substantially higher fraction of tumour cells are irradiated in G2/M after CLDR.     

Differential effects of CLDR and PDR brachytherapy on cell cycle progression in a syngeneic rat prostate tumour model

Purpose: The study consisted of two treatment arms comparing the effects of CLDR (continuous low dose rate) and PDR (pulsed dose rate) brachytherapy on cell cycle progression in a radioresistant rat prostate tumour model.

Materials and methods: Interstitial PDR and CLDR brachytherapy (both 192-Ir, 0.75 Gy/h) were administered to Dunning prostate R3327-AT1 carcinomas transplanted subcutaneously into the thigh of Copenhagen rats. Increasing doses of up to 20 as well as up to 40 Gy were applied. Cell cycle distributions of the aneuploid tumour cell subpopulations were determined at 4 h (3 Gy), 24 h (18 Gy), 48 h (20 and 36 Gy), as well as during the subsequent redistribution period (20 and 40 Gy) at 72, 96, and 120 h. Tumours either implemented with an empty tubing system (n = 5) or under undisturbed growth (n = 5) served as controls. Three animals were irradiated per time point and exposure condition. At least two flow cytometrical analyses were carried out per animal.

Results: The aneuploid cells possessed a constant DNA-Index of 1.9 ± 0.06. In contrast to sham-treated controls, the aneuploid cell fraction with G2/M DNA content was significantly increased (p < 0.05) after initiation of both, CLDR and PDR brachytherapy. However, CLDR resulted in an earlier accumulation of tumour cells in G2/M (24 h: 28% CLDR vs. 19% PDR, p < 0.05) with a concomitant reduction of cells in G1, whereas PDR yielded delayed, but then more pronounced cell cycle changes, particularly expressed during the redistribution period after both 20 and 40 Gy.

Conclusion: CLDR and PDR brachytherapy showed differential effects on cell cycle progression. The induction of a significantly earlier but also less persistent G2/M cell cycle arrest after CLDR compared to PDR brachytherapy implies that a substantially higher fraction of tumour cells are irradiated in G2/M after CLDR.     

Dose-dependent differential effects of low and pulsed dose-rate brachytherapy in a radioresistant syngenic rat prostate tumour model

Purpose : To study the response of the Dunning prostate carcinoma (R3327-AT1 subline) to continuous low dose-rate (CLDR) and pulsed dose-rate (PDR) brachytherapy. Materials and methods : After subcutaneous tumour transplantation into the thigh of the Copenhagen rat, doses of 0, 20, 30, 40 and 50 Gy were applied to the tumour surface (tumour diameter 9 ±1mm). Eight animals were irradiated per dose group and exposure condition. Interstitial PDR (192 Ir source, 37 GBq) and CLDR (192 Ir seed, 150 MBq) brachytherapy were carried out with 0.75 Gy/pulse h -1 and a dose-rate of 0.75Gyh -1, respectively. Treatment response was assessed in terms of growth delay expressed as the time (T 5) required for each tumour to reach five times the initial tumour volume. Results : The median T 5 times for the CLDR groups (in the order: control, 20, 30, 40, 50 Gy) were 12 (12), 54.5 (21), 64.5 (31), 85.5 (51), and 65 (47.5) days. Values after PDR brachytherapy are given in parentheses and resulted in a significantly impaired tumour growth delay (log-rank test) in the 20Gy (p =0.006) and 30 Gy (p =0.036) groups. No significant difference was found in the 40-50 Gy dose range. Conclusions : In contrast to previous results and predictions of biological models we observed dose-dependent differential effects of PDR and CLDR brachytherapy with reduced efficacy of PDR in the lower dose range.     

Effekte von Fraktionierung und Dosisleistung bei der PDR-Brachytherapie von B14-Zellen

Purpose

Present radiobiological studies for different cell lines in vitro demonstrate the equivalence and efficacy of continuous low-dose-rate brachytherapy (LDR-BT) and pulsed dose rate brachytherapy (PDR-BT) when using small and frequent dose pulses. The aim of this study was to examine monolayer fibroblast cultures in vitro to examine the biological effects of different pulse doses and dose rates under clinically conditiones.

Material and Methods

B14 cells, Hy B14 FAF 28, peritoneal fibroblasts, were cultured in multi-well plates and exposed to a PDR radiation source at a distance of 9 mm. The following PDR-schemes were compared: dose per pulse: 1 Gy, 2.5 Gy and 5 Gy to a total dose of 5 Gy/5 h (overall time). 10 Gy/10 h, 20 Gy/20 h and 30 Gy/30 h. The pulse duration for the examination of dose rate effects was 20 min, 30 min or 52 min corresponding to a pulse dose rate of 300 cGy/h, 200 cGy/h or 115 cGy/h. Treatment endpoints were cell survival measured by dye exclusion test and clonogenic cell survival.

Results

Cell survival decreased for pulse doses of 5 Gy compared to 2.5 Gy or 1 Gy per pulse (mean dose rate 200 to 300 cGy/h). No differences were observed with dose rates during irradiation of 300 cGy/h, 200 cGy/h or 115 cGy/h (20 Gy/l Gy).

Conclusion

Radiobiological effects of PDR-BT are dependent on the dose per pulse, with differences in biological effects only with a dose per pulse of more than 2.5 Gy, considering the described in-vitro conditiones. More examinations with a more pronounced difference in dose rate will be continued for evaluation of dose rate effects.     

5-Year Results of Pulsed Dose Rate Brachytherapy Applied as a Boost after Breast-Conserving Therapy in Patients at High Risk for Local Recurrence from Breast Cancer

PURPOSE: The aim of this study was to evaluate effect, toxicity, and cosmesis of a prospectively applied pulsed dose rate (PDR) brachytherapy boost schedule in patients with stage I/II/IIIa invasive breast cancer. PATIENTS AND METHODS: A total of 113 patients were treated after breast-conserving surgery (BCS) and external beam radiotherapy (median 50 Gy, range 46-52). The boost dose was graded in accordance to the pathologic tumor characteristics: 20-25 Gy: incomplete resection (n = 34), vascular invasion (n = 27), close margin resection (n = 41); 15 Gy: T2G3 stage (n = 11). PDR brachytherapy (37 GBq, (192)Ir source) was carried out after geometric volume optimization with 1 Gy/pulse/h. The implantation and dose specification were performed similar to the rules of the Paris system. RESULTS: The overall local failure rate after a median follow-up of 61 months was 4.4% (5/113). The actuarial 5- and 8-year local recurrence-free survival rates were 95% and 93%, respectively. Cosmesis was rated by 90% of the patients as excellent or good. 14/113 patients experienced grade III (all caused by planar telangiectasia) and none of the patients grade IV late toxicity of the skin (RTOG/EORTC). A boost dose of 25 Gy resulted in a significantly higher rate of late toxicity (Fisher's exact test, p < 0.01). CONCLUSIONS: PDR brachytherapy is safe, effective, and provides good cosmesis. A CLDR breast boost can be replaced by PDR brachytherapy without significant loss of therapeutic ratio.     

Dose-dependent differential effects of low and pulsed dose-rate brachytherapy in a radioresistant syngenic rat prostate tumour model

PURPOSE: To study the response of the Dunning prostate carcinoma (R3327-AT1 subline) to continuous low dose-rate (CLDR) and pulsed dose-rate (PDR) brachytherapy. MATERIALS AND METHODS: After subcutaneous tumour transplantation into the thigh of the Copenhagen rat, doses of 0, 20, 30, 40 and 50 Gy were applied to the tumour surface (tumour diameter 9+/-1mm). Eight animals were irradiated per dose group and exposure condition. Interstitial PDR ((192)Ir source, 37 GBq) and CLDR ((192)Ir seed, 150 MBq) brachytherapy were carried out with 0.75 Gy/pulse h(-1) and a dose-rate of 0.75Gyh(-1), respectively. Treatment response was assessed in terms of growth delay expressed as the time (T(5)) required for each tumour to reach five times the initial tumour volume. RESULTS: The median T(5) times for the CLDR groups (in the order: control, 20, 30, 40, 50 Gy) were 12 (12), 54.5 (21), 64.5 (31), 85.5 (51), and 65 (47.5) days. Values after PDR brachytherapy are given in parentheses and resulted in a significantly impaired tumour growth delay (log-rank test) in the 20Gy (p =0.006) and 30 Gy (p =0.036) groups. No significant difference was found in the 40-50 Gy dose range. CONCLUSIONS: In contrast to previous results and predictions of biological models we observed dose-dependent differential effects of PDR and CLDR brachytherapy with reduced efficacy of PDR in the lower dose range.     

3D-CT-geplante interstitielle HDR-Brachytherapie + perkutane Bestrahlung und Chemotherapie bei inoperablen Pankreaskarzinomen

Purpose

Clinical experiences in interstitial 192-iridium HDR brachytherapy for the treatment of unresectable pancreatic carcinoma are presented. Brachytherapy has been used as boost irradiation in a multimodality treatment concept together with external radiotherapy and simultaneous chemotherapy. Practicability during clinical routine, tolerability and toxicity of treatment are investigated.

Patients and Methods

Nineteen patients (9 female, 10 male, median age 67 years) with unresectable carcinoma of the pancreas have been treated with interstitial brachytherapy. Distribution according to UICC stages showed 4, 10 and 5 patients in stage II to IV respectively. In all cases afterloading technique with 192-iridium in HDR-modus was used. A total dose of 10 to 34 Gy to the reference isodose was delivered (single dose 1.88 to 5 Gy, median 2.5 Gy). Brachytherapy was followed by external radiotherapy, delivering an additional dose of 40 to 58 Gy. Nine patients received simulatenous chemotherapy (5-fluorouracil, leucovorin). Treatment planning was performed based on CT scans, allowing spatial correlation of isodose curves to the patient’s anatomy.

Results

Median survival time was 6 months. A trend of lower survival rates with advanced stage of disease (median survival stage IV 4 months, stage II and III 6.5 months) was seen. Local control rate was 70%. Brachytherapy treatment was well tolerated, severe acute side effects were not observed. One patient developed pancreatic fistulae 4 months and 1 patient a gastric ulcer 7 months after treatment. Pain release was achieved in all patients.

Conclusions

192-iridium HDR-brachytherapy is an effective tool in the treatment of unresectable pancreatic carcinoma with a high rate of local control and a low rate of side effects and is comparable IORT or seed implantation.     

HDR and MDR intracavitary treatment for carcinoma of the uterine cervix

Aim

Treatment of carcinoma of the uterine cervix by remote afterloading brachytherapy has been accompanied with new isotopes having dose rates different from the classical low-dose rate (LDR) radium source. The dose rate conversion factor from LDR to high-dose rate (HDR) found to be around 0.54 in most studies. As regards medium-dose rate (MDR) brachytherapy, the published data are very few and the experience is still short. In this study the experience of Osaka University Hospital with micro-HDR-Selectron and Selectron-MDR, as a preliminary report of the clinical trial, is presented.

Patients and Method

From August 1991 through April 1993, a total of 45 patients with carcinoma of the uterine cervix were randomly allocated to either microSelectron-HDR or Selectron-MDR at the Osaka University Hospital. As regards HDR, dose to point A was adjusted to 32 Gy (for stages I and II), 30 Gy/4 fractions, and 22.5 Gy/3 fractions, for stages III, and IV, respectively. The corresponding values in case of MDR were 35.6, 34 Gy/4 fractions, and 25.5 Gy/3 fractions. External irradiation, according to the stage, was the same in the 2 groups. Nucletron Planning System (NPS) was used for pre-treatment dose calculation at point A, rectal and bladder wall. The dose rate at point A ranged from 24 to 75.6 cGy/min for the HDR group, while for the MDR group ranged among 174.8 to 229.6 cGy/h.

Results

The 3-year survival and loco-regional control rates for both modalities were nearly equivalent (62% and 67% for HDR and 68% and 74% for MDR). The cumulative rectal and bladder complication rates were the same in both groups (29% at 3 years), with only 1 patient (MDR-group) developed grade 3 rectal and bladder complication. In this study, point A dose rate correction factor from LDR to HDR was 0.53 and 0.6 from LDR to MDR.

Conclusion

From the previous reports from Osaka University Medical School, as well as others, HDR was proposed as an alternative to LDR brachytherapy for treatment of carcinoma of the uterine cervix. In this report, Selectron-MDR was nearly equivalent to the microSelectron-HDR as regards survival and loco-regional control rates as well as radiation-induced complication. This is a preliminary report, and the study still needs larger number of patients, and longer follow-up period.     

Protocol-based image-guided salvage brachytherapy

Purpose

To assess the overall clinical outcome of protocol-based image-guided salvage pulsed-dose-rate brachytherapy for locally recurrent prostate cancer after radiotherapy failure particularly regarding feasibility and side effects.

Patients and methods

Eighteen consecutive patients with locally recurrent prostate cancer (median age, 69 years) were treated during 2005–2011 with interstitial PDR brachytherapy (PDR-BT) as salvage brachytherapy after radiotherapy failure. The treatment schedule was PDR-BT two times with 30 Gy (pulse dose 0.6 Gy/h, 24 h per day) corresponding to a total dose of 60 Gy. Dose volume adaptation was performed with the aim of optimal coverage of the whole prostate (V₁₀₀ >?95?%) simultaneously respecting the protocol-based dose volume constraints for the urethra (D_0.1 cc <?130?%) and the rectum (D_2 cc <?50–60?%) taking into account the previous radiation therapy. Local relapse after radiotherapy (external beam irradiation, brachytherapy with J-125 seeds or combination) was confirmed mostly via choline-PET and increased PSA levels. The primary endpoint was treatment-related late toxicities—particularly proctitis, anal incontinence, cystitis, urinary incontinence, urinary frequency/urgency, and urinary retention according to the Common Toxicity Criteria. The secondary endpoint was PSA-recurrence-free survival.

Results

We registered urinary toxicities only. Grade 2 and grade 3 toxicities were observed in up to 11.1?% (2/18) and 16.7?% (3/18) of patients, respectively. The most frequent late-event grade 3 toxicity was urinary retention in 17?% (3/18) of patients. No late gastrointestinal side effects occurred. The biochemical PSA-recurrence-free survival probability at 3 years was 57.1?%. The overall survival at 3 years was 88.9?%; 22?% (4/18) of patients developed metastases. The median follow-up time for all patients after salvage BT was 21 months (range, 8–77 months).

Conclusion

Salvage PDR-brachytherapy of the prostate following local failure after radiation therapy is a treatment option with a low rate of genitourinary side effects and no late gastrointestinal side effects. The treatment efficacy in the first 3 years is promising.     

Combined treatment of inoperable carcinomas of the uterine cervix with radiotherapy and regional hyperthermia

Aim

The disappointing results for inoperable, advanced tumors of the uterine cervix after conventional radiotherapy alone necessitates improving of radiation therapy. Simultaneous chemotherapy or altered radiation fractionation, such as accelerated regimen, increase acute toxicity and treatment is often difficult to deliver in the planned manner. The purpose of this phase II study was to investigate the toxicity and effectiveness of a combined approach with radiotherapy and regional hyperthermia.

Patients and Methods

From January 1994 to October 1995 18 patients with advanced carcinomas of the uterine cervix were treated in combination with radiotherpay and hyperthermia. The patients were treated with 6 to 20 MV photons delivered by a linear accelerator in a 4-field-box technique to a total dose of 50.4 Gy in 28 fractions. In the first and fourth week 2 regional hyperthermia treatments were each applied with the Sigma-60 applicator from a BSD-2000 unit. After this a boost to the primary tumor was given with high-dose-rate iridium-192 brachytherapy by an afterloading technique with 4×5 Gy at point A to a total of 20 Gy and for the involved parametrium anterioposterior-posterioanterior to 9 Gy in 5 fractions.

Results

The acute toxicity was low and similar to an external radiotherapy alone treatment. No Grade III/IV acute toxicity was found. The median age was 47 years (range 34 to 67 years). In 16 of 18 patients a rapid tumor regression was observed during combined thermo-radiotherapy, which allowed the use of intracavitary high-dose-rate brachytherapy in these cases. Complete and partial remission were observed in 13 and 4 cases, respectively. One paitent die not respond to the treatment. The median follow-up was 24 months (range 17 to 36 months). The local tumor control rate was 48% at 2 years. Median T20, T50 and T90 values were 41.7°C (range 40.3 to 43.2°C), 41.1°C (range 39.2 to 42.5°C) and 39.9°C (range 37.7 to 41.9°C), respectively. Cumulative minutes of T90>40°C (Cum40T90) and cumulative minutes, which were isoeffective to 43°C, were calculated (CEM43T90, CEM43T50, CEM43T20). CEM43T90 was found to be a significant parameter in terms of local tumor control for the 4 hyperthermia treatments (p=0.019).

Conclusion s

This treatment modality has proved to be feasible and well tolerable. The rapid tumor shrinkage in the combined approach of radiotherapy with hyperthermia before beginning brachytherapy seems to be a good prerequisite for improving of the disappointing results in cure of advanced cancer of the uterine cervix.     

X-Ray induced changes in immunostaining of proliferating cell nuclear antigen (PCNA) in V79 hamster fibroblasts

Background

Proliferating cell nuclear antigen (PCNA) ist a 36 kD protein that is involved in DNA-replication and-repair. For V79 hamster cells, a mutated p53 and a so-called “adaptive response”, an improved radiation tolerance after pre-irradiation with low X-ray doses hours before definitive irradiation with higher doses have been reported. To better understand the role of PCNA after photon irradiation in vivo, using flow cytometry, we studied the immunochemical PCNA-staining in V79 cells after irradiation with 6-MeV photons with and without serum depletion and with and without low-dose pre-irradiation under different growth conditions.

Material and Methods

Using V79 hamster cells, BrdUrd incorporation, total and DNA-bound PCNA were measured for exponential cells and for confluent cells at different times (up to 14 days) after reaching confluence. Cells were either grown with medium containing 10% fetal calf serum (FCS) or 0.5% FCS. Six days after reaching confluence, cells were irradiated with 1 Gy (and 8 Gy for non-serum-depleted cells) (6-MV photons, 2 Gy/min). Then, immunochemical PCNA-staining was measured by flow cytometry at 0, 30, 60 and 120 min after irradiation. For studying the adaptive response, exponentially growing cells and cells that were 6 days in confluence were pretreated with 0.01 Gy, reincubated for 5 h and then definitively treated with 1 Gy and harvested and processed as described above.

Results

Four days after reaching confluence, DNA-bound PCNA and BrdUrd content were reduced to a minimum of <15% positive cells while total PCNA remained essentially unchanged. After irradiation with 1 Gy 6 days after reaching confluence, cells grown with 10% FCS showed a moderate but distinct transient increase in DNA-bound PCNA at 30 min after irradiation. After irradiation with 8 Gy, there was no clear increase at 30 min but a more distinct decrease at 60 min, implying that the increase might occur earlier in the time course at higher doses. Total cellular PCNA and BrdUrd uptake were constant during the first 2 hours after irradiation. In cells that were kept with serum depleted’ medium for 6 days after reaching confluence, total PCNA was reduced and no changes in either DNA-bound PCNA or BrdUrd-uptake were observed after irradiation. When cells were primed with a dose of 0.01 Gy 5 h before subsequent treatment with 1 Gy, neither for exponentially growing cells nor for those in confluence a significant difference in the detected amount of PCNA (total and DNA-bound) or BrdUrd was observed when compared to cells treated without a priming dose.

Conclusions

The moderate X-ray induced DNA association of PCNA is indicative for ongoing DNA repair but appears to require serum stimuli. However, this p53-independent pathway involving PCNA does not seem to be the most relevant for survival in these rodent cells that tolerate much residual damage. Furthermore, no adaptive response for DNA-association of PCNA could be detected in V79 cells.     

5-Year Results of Pulsed Dose Rate Brachytherapy Applied as a Boost after Breast-Conserving Therapy in Patients at High Risk for Local Recurrence from Breast Cancer

Purpose: The aim of this study was to evaluate effect, toxicity, and cosmesis of a prospectively applied pulsed dose rate (PDR) brachytherapy boost schedule in patients with stage I/II/IIIa invasive breast cancer. Patients and Methods: A total of 113 patients were treated after breast-conserving surgery (BCS) and external beam radiotherapy (median 50 Gy, range 46-52). The boost dose was graded in accordance to the pathologic tumor characteristics: 20-25 Gy: incomplete resection (n = 34), vascular invasion (n = 27), close margin resection (n = 41); 15 Gy: T2G3 stage (n = 11). PDR brachytherapy (37 GBq, ¹⁹²Ir source) was carried out after geometric volume optimization with 1 Gy/pulse/h. The implantation and dose specification were performed similar to the rules of the Paris system. Results: The overall local failure rate after a median follow-up of 61 months was 4.4% (5/113). The actuarial 5- and 8-year local recurrence-free survival rates were 95% and 93%, respectively. Cosmesis was rated by 90% of the patients as excellent or good. 14/113 patients experienced grade III (all caused by planar telangiectasia) and none of the patients grade IV late toxicity of the skin (RTOG/EORTC). A boost dose of 25 Gy resulted in a significantly higher rate of late toxicity (Fisher's exact test, p < 0.01). Conclusions: PDR brachytherapy is safe, effective, and provides good cosmesis. A CLDR breast boost can be replaced by PDR brachytherapy without significant loss of therapeutic ratio. Ziel: Diese Studie diente der Evaluierung von Effektivität, Toxizität und kosmetischen Ergebnissen eines prospektiv applizierten PDR- (pulsed dose-rate-)Brachytherapieboostkonzeptes bei Patienten mit invasivem Mammakarzinom im Stadium I/II/IIIa. Patienten und Methoden: Insgesamt wurden 113 Patienten nach brusterhaltender Therapie (BET) und externer Bestrahlung (Median 50 Gy, Range 46-52) behandelt. Die Boostdosis wurde anhand histopathologischer Tumorcharakteristika graduiert (Tabelle 1): 20-25 Gy: inkomplette Resektion (n = 34), Lymphgefäß- oder Gefäßinvasion (n = 27), "close-margin"-Resektion (n = 41); 15 Gy: T2G3 Stadium (n = 11). Die gepulste Brachytherapie (37 GBq, ¹⁹²Ir-Quelle) wurde nach geometrischer Volumenoptimierung mit 1 Gy/Puls/h durchgeführt. Applikation und Dosisspezifikation erfolgten in Anlehnung an das Pariser System. Ergebnisse: Die Lokalrezidivrate betrug nach einer medianen Nachbeobachtungszeit von 61 Monaten 4,4% (5/113). Das aktuarische lokalrezidivfreie 5- und 8-Jahres-Überleben betrug 95% bzw. 93% (Abbildungen 1 und 2). 90% der Patienten beurteilten ihre kosmetischen Ergebnisse als gut oder exzellent (Tablle 3). Bedingt durch flächige Teleangiektasien im Boostareal entwickelten 14/113 Patienten eine Grad-III-Spättoxizität (0/113 Grad IV) der haut (RTOG/EORTC, Tabelle 2). Eine Boostdosis von 25 Gy resultierte in einer signifikant erhöhten Spättoxizitätsrate (Fishers Exakt-Test, p < 0,01, Abbildung 3). Schlussfolgerung: Die gepulste Brachytherapie ist sicher und effektiv. Die kosmetischen Ergebnisse sind gut. Der interstitielle CLDR-Mammaboost kann durch die PDR-Brachytherapie ohne signifikanten Verlust an therapeutischer Breite ersetzt werden.     

Effects of bone marrow or mesenchymal stem cell transplantation on oral mucositis (mouse) induced by fractionated irradiation

Background and purpose

Oral mucositis is a severe and dose limiting early side effect of radiotherapy for head-and-neck tumors. This study was initiated to determine the effect of bone marrow- and mesenchymal stem cell transplantation on oral mucositis (mouse tongue model) induced by fractionated irradiation.

Material and methods

Daily fractionated irradiation (5?×?3 Gy/week) was given over 1 (days 0–4) or 3 weeks (days 0–4, 7–11, 14–18). Each protocol was terminated (day 7 or 21) by graded test doses (5 dose groups, 10 animals each) in order to generate complete dose–effect curves. The incidence of mucosal ulceration, corresponding to confluent mucositis grade 3 (RTOG/EORTC), was analyzed as the primary, clinically relevant endpoint. Bone marrow or mesenchymal stem cells were transplanted intravenously at various time points within these fractionation protocols.

Results

Transplantation of 6?×?10⁶, but not of 3?×?10⁶ bone marrow stem cells on day ??1, +?4, +?8, +?11 or +?15 significantly increased the ED₅₀ values (dose, at which an ulcer is expected in 50?% of the mice); transplantation on day +?2, in contrast, was ineffective. Mesenchymal stem cell transplantation on day ??1, 2 or +?8 significantly, and on day +?4 marginally increased the ED₅₀ values.

Conclusion

Transplantation of bone marrow or mesenchymal stem cells has the potential to modulate radiation-induced oral mucositis during fractionated radiotherapy. The effect is dependent on the timing of the transplantation. The mechanisms require further investigation.     

Prospektive Studie zur Vermeidung heterotoper Ossifikationen nach Hüftgelenksersatz

Purpose

Two prospective trials were undertaken to assess the comparative efficacy of early postoperative irradiation with different radiation doses versus the postoperative use of nonsteroidal antiinflammatory drugs (NSAID) for prevention of heterotopic ossification (HO) following prothetic total hip replacement (THP).

Patients and Method

Between 1992 and 1994 585 patients received THP. These patients were randomwed in two longitudinal studies each with 3 treatment arms comparing postoperative irradiation with 4×3 Gy (101 patients), 1×5 Gy (93 patients), 1×7 Gy (95 patients) and the postoperative use of the NSAID indometacin for 7 days (113 patients) respectively for 14 days (90 patients) und acetyl salicyl acid (ASS) for 14 days (93 patients). Heterotopic ossification was scored according to the Brooker grading system. One hundred patients receiving no prophylactic therapy after total hip arthroplasty between 1988 and 1992 were analysed and defined as historical control group.

Results

Incidence of heterotopic ossification was 5% in the 4×3 Gy group (Brooker grade I 5%, grade II 0%, grade III 0%), 30,5% in the 1×5 Gy group (Brooker grade I 24,7%, grade II 4,1%, grade III 1.0%) and 10,5% in the 1×7 Gy group (Brooker grade I 10.5%, grade II 0%, grade III 0%). 15.9% of the indometacin-7 days-group developed heterotopic ossification (Brooker grade I 8%, grade II 6.2%, grade III 1.7%, grade IV 0%), 12.2% of the indometacin-14 days-group (Brooker grade I 8.9%, grade II 2.2%, grade III 1.1%) and 37.5% of the ASS-group (Brooker grade I 27.9%, grade II 4.3%, grade III 5.3%). The lowest incidence of heterotopic ossification was found for the 4××3 Gy and the 1×7 Gy group, but no significant difference between these two different treatments was observed.

Conclusion

Prophylactic irradiation of the operative site after hip replacement is more effective than the use of NSAID. Because no significant difference between the fractionated ingle dose irradiation was found and the latter is more comfortable for patients and more economical, irradiation with single 7 Gy fraction should be prefered.     

Long-term results of pulsed irradiation of skin metastases from breast cancer. Effectiveness and sequelae.

PURPOSE: The concept of pulsed brachytherapy suggested by Brenner and Hall requires an unusual fractionation scheme. Effectiveness and sequelae of this new irradiation method were observed in patients with disseminated cutaneous metastases of breast cancer. PATIENTS AND METHODS: A flexible, reusable skin mold (weight 110 g) was developed for use with a pulsed dose rate (PDR) afterloader. An array of 18 parallel catheters (2 mm diameter) at equal distances of 10 or 12 mm was constructed by fixation of the catheters in a plastic wire mesh. The array is sewn between 2 foam rubber slabs of 5 mm thickness to provide a defined constant distance to the skin. Irradiations are possible up to a maximum field size of 20 x 23.5 cm using a nominal 37 GBq Ir-192 source. Pulses of 1 Gy reference dose at the skin surface are applied at a rate of 1 pulse every 1.2 hours (0.8 Gy per hour). The dose distribution is geometrically optimized to provide a homogeneous skin dose (100% +/- 10%). The 80% dose level lies at 5 mm below the skin surface. Between April 1994 and December 1997, 52 patients suffering from cutaneous metastases at the thoracic wall were treated with 54 fields and total doses of 38 to 50 Gy (median 42 Gy) applying 2 PDR courses with a pause of 4 to 5 weeks. RESULTS: Forty-six patients (48 fields) were eligible for evaluation in June 1998. The median follow-up was 16 months (range 7.1 to 46.2 months). Local control was achieved in 40 out of 48 fields (83%) or 41 of 46 patients (89%), respectively. Moist desquamation occurred in 52% of the patients. Late reactions were judged after a minimum follow-up of 6 months. Thirty-two fields had been previously irradiated with external beam therapy to doses of 40 to 60 Gy. Regardless of whether the skin was preirradiated or not all patients surviving long enough developed telangiectasia within 2 years after PDR irradiation. In preirradiated patients (n = 32) skin contractures and/or skin necrosis occurred in 12% each. In newly irradiated patients (n = 14) no contractures or skin necrosis were observed. CONCLUSIONS: Pulsed brachytherapy is an effective and time-sparing method for the treatment of cutaneous metastases from breast cancer. Skin reactions are comparable to the sequelae of orthovoltage therapy. Two sessions of approximately 20 Gy PDR were tolerated on preirradiated skin without severe sequelae.     

Changes in RBE of 14-MeV (d+T) neutrons for V79 cells irradiated in air and in a phantom: Is RBE enhanced near the surface?

Purpose

The relative biological effectiveness (RBE) for inacivation of V79 cells was determined as function of dose at the Heidelberg 14-MeV (d+T) neutron therapy facility after irradiation with single doses in air and at different depths in a therapy phantom. Furthermore, to assess the reproducibility of RBE determinations in different experiments we examined the relationship between the interexperimental variation in radiosensitivity towards neutrons with that towards low LET⁶⁰Co photons.

Methods

Clonogenic survival of V79 cells was determined using the colony formation assay. The cells were irradiated in suspension in small volumes (1.2 ml) free in air or at defined positions in the perspex phantom. Neutron doses were in the range, D₁=0.5–4 Gy.⁶⁰Co photons were used as reference radiation.

Results

The radiosensitivity towards neutrons varied considerably less between individual experiments than that towards photons and also less than RBE. However, the mean sensitivity of different series was relatively constant. RBE increased with decreasing dose per fraction from RBE=2.3 at 4 Gy to RBE=3.1 at 0.5 Gy. No significant difference in RBE could be detected between irradiation at 1.6 cm and 9.4 cm depth in the phantom. However, an approximately 20% higher RBE was found for irradiation free in air compared with inside the phantom. Combining the two effects, irradiation with 0.5 Gy free in air yielded an approximately 40% higher RBE than a dose of 2 Gy inside the phantom

Conclusion

The measured values of RBE as function of dose per fraction within the phantom is consistent with the energy of the neutron beam. The increased RBE free in air, however, is greater than expected from microdosimetric parameters of the beam and may be due to slow recoil protons produced by interaction of multiply scattered neutrons or to an increased contribution of α particles from C(n,α) reactions near the surface. An enhanced RBE in subcutaneous layers of skin combined with an increase in RBE at low doses per fraction outside the target volume could potentially have significant consequences for normal tissue reactions in radiotherapy patients treated with fast neutrons.     

Daytime pulsed dose rate brachytherapy as a new treatment option for previously irradiated patients with recurrent oesophageal cancer

The aim of this study was to evaluate the feasibility, effects, and toxicity of pulsed dose rate (PDR) brachytherapy for re-irradiation of oesophageal carcinoma. A total of 16 patients (median age 67 years) with inoperable recurrences from oesophageal cancer after primary radio-(chemo)-therapy (median 50 Gy) were re-irradiated using PDR brachytherapy ((192)Ir, 37 GBq). Treatment was carried out on an outpatient basis applying a weekly 5 Gy daytime schedule (0.5 Gy pulse(-1) h(-1), total dose 15-20 Gy). The dose was prescribed 10 mm from the mid-dwell position and encompassed the clipped tumour extension with 2 cm margins. The use of clips for delineation of tumour extent and catheter movement during irradiations was evaluated. All 61 PDR treatments were applied safely. The median catheter movement was 5 mm, range 2-12 mm. After a median follow-up of 8 months, three patients had a complete and five a partial remission. Body weight increased in 5 of 16 (31%) and was stable in 4 of 16 (25%) patients, respectively. The median grade 2 (RTOG/EORTC) dysphagia-free survival was 17 months. Seven patients experienced grade 1, five grade 2, and one grade 3 late toxicity. Three patients with uncontrolled locoregional disease showed grade 4 complications (oesophago-tracheal fistulae (n=2), fatal arterial bleeding (n=1). Daytime PDR brachytherapy proved to be feasible and provided effective palliation. Toxicity remains a major problem. Thus, total dose should be restricted to <15 Gy in this palliative situation.     

Small bowel toxicity after high dose spot scanning-based proton beam therapy for paraspinal/retroperitoneal neoplasms

Purpose

Mesenchymal tumours require high-dose radiation therapy (RT). Small bowel (SB) dose constraints have historically limited dose delivery to paraspinal and retroperitoneal targets. This retrospective study correlated SB dose–volume histograms with side-effects after proton radiation therapy (PT).

Patients and methods

Between 1997 and 2008, 31 patients (mean age 52.1 years) underwent spot scanning-based PT for paraspinal/retroperitoneal chordomas (81?%), sarcomas (16?%) and meningiom (3?%). Mean total prescribed dose was 72.3 Gy (relative biologic effectiveness, RBE) delivered in 1.8–2 Gy (RBE) fractions. Mean follow-up was 3.8 years. Based on the pretreatment planning CT, SB dose distributions were reanalysed.

Results

Planning target volume (PTV) was defined as gross tumour volume (GTV) plus 5–7 mm margins. Mean PTV was 560.22 cm³. A mean of 93.2?% of the PTV was covered by at least 90?% of the prescribed dose. SB volumes (cm³) receiving doses of 5, 20, 30, 40, 50, 60, 70, 75 and 80 Gy (RBE) were calculated to give V5, V20, V30, V40, V50, V60, V70, V75 and V80 respectively. In 7/31 patients, PT was accomplished without any significant SB irradiation (V5?=?0). In 24/31 patients, mean maximum dose (Dmax) to SB was 64.1 Gy (RBE). Despite target doses of >?70 Gy (RBE), SB received >?50 and >?60 Gy (RBE) in only 61 and 54?% of patients, respectively. Mean SB volumes (cm³) covered by different dose levels (Gy, RBE) were: V20 (n?=?24): 45.1, V50 (n?=?19): 17.7, V60 (n?=?17): 7.6 and V70 (n?=?12): 2.4. No acute toxicity ≥ grade 2 or late SB sequelae were observed.

Conclusion

Small noncircumferential volumes of SB tolerated doses in excess of 60 Gy (RBE) without any clinically-significant late adverse effects. This small retrospective study has limited statistical power but encourages further efforts with higher patient numbers to define and establish high-dose threshold models for SB toxicity in modern radiation oncology.     

Dosimetric study of CO-60 source step size in uterine cervix intracavitary HDR brachytherapy

Purpose

The present work reports effects of source step sizes on dose distribution in patients treated with cobalt-60 (Co-60) high-dose-rate afterloading brachytherapy in carcinoma cervix (Ca-cx).

In vivo dosimetry with semiconductors in medium dose rate (MDR) brachytherapy for cervical cancer

Purpose

This study was performed to evaluate the role of in vivo dosimetry with semiconductor detectors in gynaecological medium dose rate brachytherapy, and to compare the actual doses delivered to organs at risk (as measured using in vivo dosimetry) with those calculated during treatment planning.

Materials and methods

Doses to the rectum and bladder were measured in a group of patients with cervical carcinoma using semiconductor detectors and compared to the doses calculated using a treatment planning system. 36 applications of brachytherapy at dose rates of 1.8–2.3 Gy/h were performed in the patients.

Results

The mean differences between the measured and calculated doses were 3 % for the rectum and 11 % for the bladder.

Conclusions

The main reason for the differences between the measured and calculated doses was patient movement. To reduce the risk of large errors in the dose delivered, in vivo dosimetry should be performed in addition to treatment planning system computations.