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.     

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.     

In-vitro-Untersuchungen zur PDR-Brachytherapie

Background

Calculations on the basis on the LQ-model have been focussed on the possible radiobiological equivalence between common continuous low dose rate irradiation (CLDR) and a superfractionated irradiation (PDR=pulsed dose rate) provided that the same total dose will be prescribed in the same overall time as with the low doserate. A clinically usable fractionation scheme for brachytherapy was recommended by Brenner and Hall and should replace the classical CLDR brachytherapy with line sources with an afterloading technique using a stepping source. The hypothesis that LDR equivalency can be achieved by superfractionation was tested by means of in vitro experiments on V79 cells in monolayer and spheroid cultures as well as on HeLa monolayers.

Materials and Methods

Simulating the clinical situation in PDR brachytherapy, fractionation experiments were carried out in the dose rate gradient of afterloading sources. Different dose levels were produced with the same number of fractions in the same overall incubation time. The fractionation schedules which were to be compared with a CLDR reference curve were: 40×0.47 Gy, 20×0.94 Gy, 10×1.88 Gy, 5×3.76 Gy, 2×9.4 Gy given in a period of 20 h and 1×18.8 Gy as a “single dose” exposition. As measured by flow cytometry, the influence of the dose rate in the pulse on cell survival and on cell cycle distribution under superfractionation was examined on V79 cells.

Results

V79 spheroids as a model for a slowly growing tumor, reacted according to the radiobiological calculations, as a CLDR equivalency was achieved with increasing fractionation. Rapidly growing V79 monolayer cells showed an inverse fractionation effect. A superfractionated irradiation with pulses of 0.94 Gy/h respectively 0.47 Gy/0.5 h was significantly more effective than the CLDR irradiation. This inverse fractionation effect in log-phase V79 cells could be attributed to the accumulation of cycling cells in the radiosensitive G2/M phase (G2 block) during protected exposure which was drastically more pronounced for the pulsed scheme. HeLa cells were rather insensitive to changes of fractionation. Superfractionation as well as hypofractionation yielded CLDR equivalent survival curves.

Conclusions

The fractionation scheme, derived from the PDR theory to achieve CLDR equivalent effects, is valid for many cell lines, however not for all. Proliferation and dose rate dependend cell cycle effects modify predictions derived from the sublethal damage recovery model and can influence acute irradiation effects significantly. Dose rate sensitivity and rapid proliferation favour cell cycle effects and substantiate, applied to the clinical situation, the possibility of a higher effectiveness of the pulsed irradiation on rapidly growing tumors.     

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 brachytherapy: an option for preventing nonmalignant obstruction in patients after lung transplantation

Purpose

Interventional bronchoscopy is the main treatment modality in managing benign airway obstructions following lung transplantation. We analyzed the effect of intraluminal brachytherapy on preventing recurrence of hyperplastic tissue.

Patients and methods

From September 2002 to September 2004, a total of 24 intraluminal brachytherapy applications were carried out on 12 lung transplant patients in 15 different locations. A single dose of 3?Gy was calculated at a 5-mm distance from the catheter surface; the target volume included a stenosis plus safety interval of 0.5?C1.0?cm.

Results

All patients had a mean 10.6 local interventions (Argon plasma coagulation, balloon dilatations, stenting) over 4.4?months before the first application of endobronchial brachytherapy, with a mean amount of 2.4 applications per month. The mean forced expiratory volume in 1?s (FEV1) was 2,219?ml in the 3?months before application of brachytherapy. After endobronchial brachytherapy, all patients experienced improvement in clinical status and respiratory function. The mean level of FEV1 in the 3?months after application was 2,435?ml (p?=?0.02), and the number of invasive interventions dropped to a mean rate of 5.2 interventions in the 5.1?months after the first intervention, with an amount of 1 application per month. No treatment-related complications were seen. Four patients were treated twice, 1?patient three times, and 1?patient four times at the same localization.

Conclusions

Recurrent symptomatic benign airway obstruction from hyperplastic tissue in the bronchus after lung transplantation can be successfully treated with intraluminal high-dose-rate brachytherapy with a dose of 3?Gy at a 5-mm distance from the catheter surface and a longitudinal safety margin of 1?cm.     

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.     

Locally advanced verrucous carcinoma of the oral cavity

Background

Oral verrucous carcinomas are locally invasive but rarely metastasize. Current treatment options include surgery and external beam radiotherapy (EBRT). In medical inoperable patients or irresectable tumors, high-dose-rate (HDR) brachytherapy is a valid alternative.

Case

We present an 85-year-old man with functionally irresectable cT3N0M0 verrucous carcinoma superficially spreading along the upper alveolar ridge to the retro-alveolar triangle, with infiltration of the left soft and hard palate and buccal mucosa. Using a customized intraoral mold, this patient was treated with HDR brachytherapy delivering a dose of 48 Gy in 12 fractions three times per week. Treatment was well tolerated, and after prolonged confluent mucositis the tumor is in complete remission.

Review of literature and conclusion

The scarce literature on customized mold HDR brachytherapy in maxillary tumors is reviewed and recommendations for other head and neck tumors are given.     

Die testikuläre intraepitheliale Neoplasie (TIN)

Background

Testicular intraepithelial neoplasia (TIN), synonymous for carcinoma in situ of the testis, is a rarely observed preinvasive neoplasia located within the germinative epithelium. According to the current knowledge of the biology of TIN, it is the common precursor of all testicular germ cell neoplasms except spermatocytic seminoma.

Material and Methods

This report provides a review of histopathology, epidemiology and diagnostic procedures for TIN and discusses the therapeutic options with particular respect to radiooncological aspects.

Results

TIN has a 70% rate of progression to invasive cancer within 7 years. Depending on the individual therapeutic setting surgery, chemotherapy and radiotherapy are alternative treatment modalities. In case of TIN in a single testis or bilateral TIN, local radiotherapy is the standard procedure. With 20 Gy recommended as standard dose in Germany, radiotherapy yields safe eradication of TIN. However, some of the patients show significantly reduced synthesis of testicular androgens. With respect to sporadic reports in the literature, total doses well below 20 Gy might be equally efficient to treat TIN safely. Yet, up to date neither the minimum dose for efficient treatment nor the toxicity profile after consecutive chemo-radiotherapy has been established.

Conclusions

The currently recommended standard dose of 20 Gy in Germany is probably in excess of the minimum dose needed for safe eradication of TIN. Thus, new radiooncological strategies should aim at reducing the total dose of treatment in order to minimize late side effects while maintaining the high efficacy of radiotherapy. This topic is under investigation in a multicenter clinical trial.     

Modeling the absorbed dose to the common carotid arteries following radioiodine treatment of benign thyroid disease

Introduction

External fractionated radiotherapy of cancer increases the risk of cardio- and cerebrovascular events, but less attention has been paid to the potential side effects on the arteries following internal radiotherapy with radioactive iodine (RAI), i.e. 131-iodine. About 279 per million citizens in the western countries are treated each year with RAI for benign thyroid disorders (about 140,000 a year in the EU), stressing that it is of clinical importance to be aware of even rare radiation-induced side effects. In order to induce or accelerate atherosclerosis, the dose to the carotid arteries has to exceed 2 Gy which is the known lower limit of ionizing radiation to affect the endothelial cells and thereby to induce atherosclerosis.

Objective

To estimate the radiation dose to the carotid arteries following RAI therapy of benign thyroid disorders.

Methods

Assuming that the lobes of the thyroid gland are ellipsoid, that the carotid artery runs through a part of the lobes, that there is a homogeneous distribution of RAI in the lobes, and that the 24 h RAI uptake in the thyroid is 35 % of the ¹³¹I orally administrated, we used integrated modules for bioassay analysis and Monte Carlo simulations to calculate the dose in Gy/GBq of administrated RAI.

Results

The average radiation dose along the arteries is 4–55 Gy/GBq of the ¹³¹I orally administrated with a maximum dose of approximately 25–85 Gy/GBq. The maximum absorbed dose rate to the artery is 4.2 Gy/day per GBq ¹³¹I orally administrated.

Conclusion

The calculated radiation dose to the carotid arteries after RAI therapy of benign thyroid disorder clearly exceeds the 2 Gy known to affect the endothelial cells and properly induce atherosclerosis. This simulation indicates a relation between the deposited dose in the arteries following RAI treatment and an increased risk of atherosclerosis and subsequent cerebrovascular events such as stroke.     

Endovaskuläre Ir-192-HDR-Brachytherapie zur Vermeidung einer intimalen Hyperplasie in peripheren Gefäßen nach PTA und Stentimplantation

Background

The percutaneous transluminal angioplasty (PTA) is the “golden standard” in the therapy of vessel occlusions due to arteriosclerotic plaques. In spite of all improvements of the technique and the equipment with and without stent implantation there is still a restenosis rate of 40%.

Patients and Methods

Endovascular brachytherapy with an iridium-192 HDR source was performed in cases of a restenosis due to intimal hyperplasia which occurred within 6 months after a former PTA. After PTA and stent implantation a 9-French ReKa catheter was positioned with the tip 2 cm below the stent. This catheter served a centering device and as a guide for the 5-French appliator. After determination of the isodose and individual planning a dose of 12 Gy to 3 mm source distance was applied. After this procedure the patient received heparin for 72 hours followed by marcumar.

Results

From May 1990 until June 1996 28 patients (21 male, 7 female) were treated after PTA and stent implantation with endovascular brachytherapy. All patients had clinical relevant restenosis or reocclusion of the arteria femoralis. The follow-up time ranges from 2 to 71 months. Twenty-seven patients had a reasonable follow-up time longer than 6 months. Twenty-five patients could be followed: 4 patients had no or only minimal flow in the treated area, 2 patients moved with an unknown address, 1 patient died without any follow-up examination. No side effects of the radiation appeared.

Conclusion

Regarding the small number of patients endovascular brachytherapy with iridium 192 HDR seems to be a save and useful adjuvant treatment form to avoid intimal hyperplasia after PTA.     

Dose-escalated simultaneous integrated-boost treatment of prostate cancer patients via helical tomotherapy

Purpose

The goal of this work was to assess the feasibility of moderately hypofractionated simultaneous integrated-boost intensity-modulated radiotherapy (SIB-IMRT) with helical tomotherapy in patients with localized prostate cancer regarding acute side effects and dose–volume histogram data (DVH data).

Methods

Acute side effects and DVH data were evaluated of the first 40 intermediate risk prostate cancer patients treated with a definitive daily image-guided SIB-IMRT protocol via helical tomotherapy in our department. The planning target volume including the prostate and the base of the seminal vesicles with safety margins was treated with 70?Gy in 35 fractions. The boost volume containing the prostate and 3?mm safety margins (5?mm craniocaudal) was treated as SIB to a total dose of 76?Gy (2.17?Gy per fraction). Planning constraints for the anterior rectal wall were set in order not to exceed the dose of 76?Gy prescribed to the boost volume. Acute toxicity was evaluated prospectively using a modified CTCAE (Common Terminology Criteria for Adverse Events) score.

Results

SIB-IMRT allowed good rectal sparing, although the full boost dose was permitted to the anterior rectal wall. Median rectum dose was 38?Gy in all patients and the median volumes receiving at least 65?Gy (V65), 70?Gy (V70), and 75?Gy (V75) were 13.5%, 9%, and 3%, respectively. No grade?4 toxicity was observed. Acute grade?3 toxicity was observed in 20% of patients involving nocturia only. Grade?2 acute intestinal and urological side effects occurred in 25% and 57.5%, respectively. No correlation was found between acute toxicity and the DVH data.

Conclusion

This institutional SIB-IMRT protocol using daily image guidance as a precondition for smaller safety margins allows dose escalation to the prostate without increasing acute toxicity.     

Radiotherapy of glioblastoma multiforme

Purpose

With regard to the poor prognosis of patients with glioblastoma multiforme, the aspect of life quality with a minimal treatment time becomes essential. The purpose of the present study is to evaluate whether the results of a radiotherapy schedule using increased single fractions applied over a shortened treatment time is feasible without compromising treatment efficiency or providing more side effects than a conventionally fractionationed treatment.

Patients and Methods

A total of 38 patients (f=21, m=17, mean age 58 years) with histologically proven glioblastoma multiforme were irradiated after (partial) resection (n=29) or stereotactic surgery (n=9) with single doses of 3.5 Gy (ICRU) 5 fractions a week up to a total dose of 42 Gy following individual treatment planning.

Results

Median survival was 45.7 weeks, survival rate after 6 months was 80.9% and decreased to 34.2% after 12 months. Radiotherapy was tolerated without any important acute toxicity or any late side effects during the follow-up period.

Conclusions

The increase of the dose per fraction using a fraction size of 3.5 Gy enhanced neither acute nor late toxicity. The survival rate compared well to those described in the literature. Thus the shortened treatment schedule seems as efficient as conventional radiotherapy. Moreover, it seems preferable with regard to quality of life.     

Salvagebehandlung fortgeschrittener Plattenepithelkarzinome der Mundhöhle und des Oropharynx

Purpose

The clinical effect of high-dose-rate (HDR) interstitial brachytherapy combined with tumor resection was investigated in this retrospective study on patients with recurrent oral and oropharyngeal squamous cell carcinoma.

Patients and Methods

Oral and oropharyngeal squamous cell carcinoma in 38 patients were treated over a period of 7 years (1988–1994) by HDR interstitial brachytherapy using Gammamed 12i^® equipment. Pretreatment of patients in terms of irradiation and surgery differed (33 irradiated with a total dose between 60.0 and 75.6 Gy, including 8 patients with additional surgery; 1 patient with surgery alone, and 4 patients without any pretreatment). Indications for interstitial brachytherapy differed according to individual responses to treatment and medical histories.

Results

Interstitial brachytherapy was successful in the majority of patients, i. e. complete remission: 12, partial remission: 19, no change: 2, progression: 5. Local control and overall survival including patients with surgical treatment was 59% and 81% at 6 months and 47% and 49% after 12 months, respectively.

Conclusion

Interstitial HDR brachytherapy with Iridium 192 is recommended in patients with local recurrences or second primary carcinomas after previous external radiotherapy in the head and neck region. Combination of interstitial brachytherapy and surgery is preferable for these patients.     

Intracavitary brachytherapy for carcinoma of the uterine cervix—Comparison of HDR (Ir-192) and MDR (Cs-137)—

Purpose

To compare the results of high dose rate (HDR) (Ir-192) and medium dose rate (MDR) (Cs-137) intracavitary brachytherapy (ICRT) for carcinoma of the uterine cervix.

Materials and Methods

Between May 1991 and March 2001, a total of 206 patients with Stage I-IVA previously untreated cervical cancer were treated with ICRT combined with external beam radiotherapy (EBRT). HDR was administered to a total of 135 patients: 22 patients in Stage I, 49 in Stage II, 56 in Stage III, and eight in Stage IVA. MDR was administered to a total of 71 patients: six patients in Stage I, 27 in Stage II, 33 in Stage III, and five in Stage IVA. The MDR at point A was 30 Gy/hour for HDR and 1.7 Gy/hour for MDR treatment, and the corresponding median follow-up periods for survivors were 55 and 68 months.

Results

For the HDR group, 5-year cause-specific survival rates were 90%, 78%, 53% and 33% for Stages I, II, III, and IVA, respectively. For the MDR group, the corresponding rates were 100%, 76%, 51%, and 40%. In the HDR group, 19 patients (14%) developed Grade 2 or higher late complications, and, in the MDR group, four patients (6%) did.

Conclusions

There was no statistically significant difference in cause-specific survivals between the results of HDR and MDR brachytherapy for cervical cancer. The incidence of late complications tended to be higher for the HDR group than for the MDR group, but did not show a statistically significant difference (p=0.07).     

Ergebnisse der Behandlung von Rektumkarzinomrezidiven mit schnellen Neutronen (d, T 14 MeV)

Purpose

In spite of improved surgical techniques and the use of multiple modality treatment schemes the local recurrence rate of colorectal carcinomas could not be successfully reduced up to now. Besides surgical treatment of local recurrences in some cases radiation therapy may be indicated.

Patients and Method

In the Department of Radiotherapy of the University of Münster 37 patients with recurrent rectal carcinoma were treated between the end of 1985 and September 1992 either with fast neutrons alone or with a combined photon-neutron therapy. Eighteen patients received radiotherapy with fast neutrons (14 MeV d,T) alone; the tumor dose was between 10 and 15 Gy neutrons. Nineteen patients were irradiated with a mixed-beam schedule consisting of 30 to 45 Gy photons (X 10 MV) and neutron doses ranging from 5 to 10 Gy.

Results

In 30 patients a good or complete pain relief could be observed immediately after the last irradiation. Sixteen out of 37 patients had local tumor regrowth during the follow-up period. The median survival for all 37 patients was 15.9 months. The probability for survival was 86% after 6 months and 61% after 12 months (Kaplan-Meier). The side effects were slight to moderate (EORTC/RTOG I-II).

Conclusions

This therapy showed good results concerning a fast and effective pain relief. Additionally the results seem to show a good effect concerning local control and overall survival in this negatively selected patients.     

Dosimetric investigation of LDR brachytherapy 192Ir wires by Monte Carlo and TPS calculations

Purpose

The aim of this study was to investigate the dose rate distribution around ¹⁹²Ir wires used as radioactive sources in low-dose-rate brachytherapy applications.

Materials and methods

Monte Carlo modeling of a 0.3-mm diameter source and its surrounding water medium was performed for five different wire lengths (1–5 cm) using the MCNP software package.

Results

The computed dose rates per unit of air kerma at distances from 0.1 up to 10 cm away from the source were first verified with literature data sets. Then, the simulation results were compared with the calculations from the XiO CMS commercial treatment planning system.

Conclusion

The study results were found to be in concordance with the treatment planning system calculations except for the shorter wires at close distances.     

Computed tomography-guided interstitial high dose rate brachytherapy for centrally located liver tumours: a single institution study

Objectives

To evaluate the clinical outcome of computed tomography (CT)-guided interstitial (IRT) high-dose-rate (HDR) brachytherapy (BRT) in the treatment of unresectable primary and secondary liver malignancies. This report updates and expands our previously described experience with this treatment technique.

Methods

Forty-one patients with 50 tumours adjacent to the liver hilum and bile duct bifurcation were treated in 59 interventions of CT-guided IRT HDR BRT. The tumours were larger than 4 cm with a median volume of 84 cm³ (38–1,348 cm³). The IRT HDR BRT delivered a median total physical dose of 20.0 Gy (7.0–32.0 Gy) in twice daily fractions of median 7.0 Gy (4.0–10.0 Gy) in 19 patients and in once daily fractions of median 8.0 Gy (7.0–14.0 Gy) in 22 patients.

Results

With a median follow-up of 12.4 months, the local control for metastatic hepatic tumours was 89 %, 73 % and 63 % at 6, 12 and 18 months respectively. The local control for primary hepatic tumours was 90 %, 81 % and 50 % at 6, 12 and 18 months respectively. Severe side effects occurred in 5.0 % of interventions with no treatment-related deaths.

Conclusions

CT-guided IRT HDR BRT is a promising procedure for the radiation treatment of centrally located liver malignancies.

Key points

? Interstitial high-dose-rate brachytherapy (IRT HDR BRT) is a promising treatment for central liver tumours ? CT-guided IRT HDR BRT is safe for treating extensive tumours ? CT-guided IRT HDR BRT could play a role in managing unresectable hepatic malignancies     

Anmerkungen zum Problem der Dosierung in der HDR-Brachytherapie

Background

In HDR brachytherapy activity distributions can be achieved which were unknown in LDR brachytherapy. For this reason the classical dosage systems can only be used with caution in HDR brachytherapy.

Methods

Different simple applications are used to investigate the effect of various activity distributions on dose and integrated reference air kerma.

Results

Within the classical LDR dosage systems dose and integrated reference air kerma were equivalent. Due to the possibility to “opotimize” the activity distribution in HDR brachytherapy this is not longer the case. Different optimization algorithms and different optimization goals may lead to quite different activity distributions and different integrated reference air kerma values even if the source positions are the same. For target volume oriented optimization schemes a dosage system is described which is based on dose-volume-histograms.

Conclusions

A widely accepted dosage system in HDR brachytherapy is missing. The dosage system described in this paper may be useful in solving this problem.