Small field dosimetry for the small animal radiotherapy research platform (SARRP)

Background

Preclinical radiation biology has become increasingly sophisticated due to the implementation of advanced small animal image guided radiation platforms into laboratory investigation. These small animal radiotherapy devices enable state-of-the-art image guided therapy (IGRT) research to be performed by combining high-resolution cone beam computed tomography (CBCT) imaging with an isocentric irradiation system. Such platforms are capable of replicating modern clinical systems similar to those that integrate a linear accelerator with on-board CBCT image guidance.

Methods

In this study, we present a dosimetric evaluation of the small animal radiotherapy research platform (SARRP, Xstrahl Inc.) focusing on small field dosimetry. Physical dosimetry was assessed using ion chamber for calibration and radiochromic film, investigating the impact of beam focus size on the dose rate output as well as beam characteristics (beam shape and penumbra). Two film analysis tools) have been used to assess the dose output using the 0.5 mm diameter aperture.

Results

Good agreement (between 1.7–3%) was found between the measured physical doses and the data provided by Xstrahl for all apertures used. Furthermore, all small field dosimetry data are in good agreement for both film reading methods and with our Monte Carlo simulations for both focal spot sizes. Furthermore, the small focal spot has been shown to produce a more homogenous beam with more stable penumbra over time.

Conclusions

FilmQA Pro is a suitable tool for small field dosimetry, with a sufficiently small sampling area (0.1 mm) to ensure an accurate measurement. The electron beam focus should be chosen with care as this can potentially impact on beam stability and reproducibility.

     

卵巢移位术在保留盆腔肿瘤患者生育能力的应用(英文)

Objective: The aim of the study was to assess the hormonal profile level in females with pelvic tumors after surgical transposition of the ovaries during surgery followed by postoperative radiotherapy to the pelvis. Methods: Fifteen patients with rectal, bladder and cervical cancer were included in the study with their age ranged between 25 and 40 years old, 7 patients with cancer rectum, 3 patients with bladder cancer and 5 had cancer cervix. Ovarian transposition was done for patients during surgery followed by external beam radiotherapy to the pelvis, hormonal assessment was done for the patients before and after exposure to radiation. Results: No intra-operative or post-operative morbidity was observed in patients treated by laparotomy. Patients were found to have regular menstrual cycles. Their FSH, LH and progesterone levels were within normal ranges. Conclusion: Proper transposition of ovaries during laparotomy away from the radiation field can preserve the ovarian function in patients with pelvic tumors.     

The role of radiotherapy in the management of progressive glioblastoma

Question

Can re-irradiation (by using conventional radiotherapy, fractionated radiosurgery, or single fraction radiosurgery) be used in patients with progressive glioblastoma multiforme after the first adjuvant combined multimodality treatment with radiation and chemotherapy?

Target population

These recommendations apply to adult patients with progressive glioblastoma after first line combined multimodality treatment with chemotherapy and radiation.

Recommendations

Level III

When the target tumor is amenable for additional radiation, re-irradiation is recommended as it provides improved local tumor control, as measured by best imaging response. Such re-irradiation can take the form of conventional fractionation radiotherapy, fractionated radiosurgery, or single fraction radiosurgery.

Level III

Re-irradiation is recommended in order to maintain or improve a patient’s neurological status and quality of life prior to any further tumor progression.     

Do comorbidity influences acute toxicity and outcome in elderly patients with endometrial cancer treated by adjuvant radiotherapy plus brachytherapy?

Purpose

To correlate comorbidity and acute radiation toxicity in elderly patients treated with adjuvant external beam radiotherapy (EBRT) plus brachytherapy-high dose rate (HDR-BRT) for endometrial cancer (EC).

Methods

Endometrial cancer patients over 65 were treated and evaluated for comorbidity assessment with ACE-27 and Charlson comorbidity index (CCI). EBRT total dose was 45–50.4 Gy (1.8 Gy/day). The vault vagina boost of dose was performed by HDR-BRT with 2/3 fractions with a total dose of 10–15 Gy.

Results

From 2008 to 2011, 35 patients were analyzed. Eighteen patients (51.43 %) had not ACE-27 comorbidity; while 27 patients (77.14 %) had CCI lower than three. During treatment, acute toxicity was mild and not influenced by the comorbidity score. Two-year Progression Free and Overall Survival were 69 and 80 %. ACE-27 and CCI did not affect progression-free survival (p = 0.51, p = 0.3) and OS (p = 0.26, p = 0.5).

Conclusion

External beam radiotherapy plus BRT-HDR are well tolerated in EC elderly with good performance status and low comorbidity profile.     

CT模拟技术的质量保证:使用Z幻影技术测试治疗床和旋转架(英文)

Objective:The main purpose of this work was to present a Z-phantom manufactured in home (at National Cancer Institute Cairo University) and it’s use in a simple way to check the accuracy of the computed-tomography (CT) table movement and CT gantry tilt, also the other general quality control (QC) tests of the CT simulator used at radiotherapy department. Methods:The laser phantom was used to check the external mobile laser position accuracy, for internal image indicator laser beam (light field) the coincidence between light field and radiation exposure at CT simulator was checked using X-Omat ready back film. The Z-phantom was used to check the slice thickness and the table movement and so the gantry tilts. The image quality testes were checked using the CT image quality phantom. TLDs were inserted to the Cicil phantom at the center of each scan volume to estimate the patient dose. Results:The results showed that the difference in the fixed distance between the external mobile laser and the internal image indicator laser beam was less than ± 1 mm; the orientation of the two mobile lateral lasers was coincident. The mechanical movement and the image quality of the CT simulator were within the tolerances and the results were 0.5 mm, 0.2% and 0.6% for the mechanical movement, noise and image uniformity respectively. Conclusion:A CT simulator with a good performance is important for the radiotherapy treatment planning specially with the extremely revolution in radiotherapy techniques, also a rotten quality assurance (QA) program is very important to be shore about the reproducibility of the CT performance. The use of Z-phantom to check the gantry tilt and the table movement is faster than the use of ready back films in these tests.     

Extremely poor postrecurrence oncological outcome for patients with recurrent mucinous ovarian cancer

Background

This study was conducted to assess the long-term clinical outcome for patients with recurrent mucinous epithelial ovarian cancer (RmOC) in comparison with recurrent serous epithelial ovarian cancer (RsOC).

Methods

Three hundred and eighty-four patients with recurrent ovarian cancer, including 340 RsOC and 44 RmOC patients, were analyzed in this study. The pathological slides were evaluated under central pathological review. The prognostic significance of clinicopathological factors was evaluated employing both uni- and multivariable analysis.

Results

The 3- and 5-year postrecurrence survival (PRS) rates of patients with RmOC were 17.3, and 6.9 %, respectively. In contrast, those of patients with RsOC were 29.8 and 18.8 %, respectively. The PRS of patients with RmOC was significantly poorer than that of patients with RsOC (PRS: P = 0.0006). Moreover, either in the presence or absence of a residual tumor (RT) at initial surgery, the PRS of patients with RmOC was markedly poorer than that of patients with RsOC [RT (?): P < 0.0001: RT (+): P = 0.0912]. In multivariable analysis, a mucinous histology predicted a significantly poorer PRS (RmOC vs. RsOC: hazard ratio (HR) 2.080, 95 % confidence interval (CI) 1.434–3.016, P = 0.0001). Confining analysis to deceased patients (N = 302), the proportion of RmOC patients who died within 12 months following recurrence was markedly higher than that of RsOC [RmOC 69.2 %, RsOC: 41.1 % (P < 0.0001)].

Conclusions

The clinical outcome after recurrence in patients with RmOC was extremely poor. This confirms that RmOC should be considered a different entity from other epithelial ovarian cancers.     

A simple quality assurance test tool for the visual verification of light and radiation field congruent using electronic portal images device and computed radiography

Background

The radiation field on most megavoltage radiation therapy units are shown by a light field projected through the collimator by a light source mounted inside the collimator. The light field is traditionally used for patient alignment. Hence it is imperative that the light field is congruent with the radiation field.

Method

A simple quality assurance tool has been designed for rapid and simple test of the light field and radiation field using electronic portal images device (EPID) or computed radiography (CR). We tested this QA tool using Varian PortalVision and Elekta iViewGT EPID systems and Kodak CR system.

Results

Both the single and double exposure techniques were evaluated, with double exposure technique providing a better visualization of the light-radiation field markers. The light and radiation congruency could be detected within 1 mm. This will satisfy the American Association of Physicists in Medicine task group report number 142 recommendation of 2 mm tolerance.

Conclusion

The QA tool can be used with either an EPID or CR to provide a simple and rapid method to verify light and radiation field congruence.     

Novel low-kVp beamlet system for choroidal melanoma

Background

Treatment of choroidal melanoma with radiation often involves placement of customized brachytherapy eye-plaques. However, the dosimetric properties inherent in source-based radiotherapy preclude facile dose optimization to critical ocular structures. Consequently, we have constructed a novel system for utilizing small beam low-energy radiation delivery, the Beamlet Low-kVp X-ray, or "BLOKX" system. This technique relies on an isocentric rotational approach to deliver dose to target volumes within the eye, while potentially sparing normal structures.

Methods

Monte Carlo N-Particle (MCNP) transport code version 5.0(14) was used to simulate photon interaction with normal and tumor tissues within modeled right eye phantoms. Five modeled dome-shaped tumors with a diameter and apical height of 8 mm and 6 mm, respectively, were simulated distinct positions with respect to the macula iteratively. A single fixed 9 × 9 mm² beamlet, and a comparison COMS protocol plaque containing eight I-125 seeds (apparent activity of 8 mCi) placed on the scleral surface of the eye adjacent to the tumor, were utilized to determine dosimetric parameters at tumor and adjacent tissues. After MCNP simulation, comparison of dose distribution at each of the 5 tumor positions for each modality (BLOKX vs. eye-plaque) was performed.

Results

Tumor-base doses ranged from 87.1–102.8 Gy for the BLOKX procedure, and from 335.3–338.6 Gy for the eye-plaque procedure. A reduction of dose of at least 69% to tumor base was noted when using the BLOKX. The BLOKX technique showed a significant reduction of dose, 89.8%, to the macula compared to the episcleral plaque. A minimum 71.0 % decrease in dose to the optic nerve occurred when the BLOKX was used.

Conclusion

The BLOKX technique allows more favorable dose distribution in comparison to standard COMS brachytherapy, as simulated using a Monte Carlo iterative mathematical modeling. Future series to determine clinical utility of such an approach are warranted.     

In vivo antitumor activity of intratumoral fludarabine phosphate in refractory tumors expressing E. coli purine nucleoside phosphorylase

Purpose

Systemically administered fludarabine phosphate (F-araAMP) slows growth of human tumor xenografts that express Escherichia coli purine nucleoside phosphorylase (PNP). However, this treatment has been limited by the amount of F-araAMP that can be administered in vivo. The current study was designed to (1) determine whether efficacy of this overall strategy could be improved by intratumoral administration of F-araAMP, (2) test enhancement of the approach with external beam radiation, and (3) optimize recombinant adenovirus as a means to augment PNP delivery and bystander killing in vivo.

Methods

The effects of systemic or intratumoral F-araAMP in mice were investigated with human tumor xenografts (300?mg), in which 10?% of the cells expressed E. coli PNP from a lentiviral promoter. Tumors injected with an adenoviral vector expressing E. coli PNP (Ad/PNP; 2?×?10¹¹ viral particles, 2?times per day?×?3?days) and the impact of radiotherapy on tumors treated by this approach were also studied. Radiolabeled F-araAMP was used to monitor prodrug activation in vivo.

Results

Intratumoral administration of F-araAMP in human tumor xenografts expressing E. coli PNP resulted in complete regressions and/or prolonged tumor inhibition. External beam radiation significantly augmented this effect. Injection of large human tumor xenografts (human glioma, nonsmall cell lung cancer, or malignant prostate tumors) with Ad/PNP followed by intratumoral F-araAMP resulted in excellent antitumor activity superior to that observed following systemic administration of prodrug.

Conclusion

Activation of F-araAMP by E. coli PNP results in destruction of large tumor xenografts in vivo, augments radiotherapy, and promotes robust bystander killing. Our results indicate that intratumoral injection of F-araAMP leads to ablation of tumors in vivo with minimal toxicity.     

A polygenic risk score for breast cancer risk in a Taiwanese population

Background

Multiple common variants identified by genome-wide association studies showed limited evidence of the risk of breast cancer in Taiwan. In this study, we analyzed the breast cancer risk in relation to 13 individual single-nucleotide polymorphisms (SNPs) identified by a GWAS in an Asian population.

Methods

In total, 446 breast cancer patients and 514 healthy controls were recruited for this case–control study. In addition, we developed a polygenic risk score (PRS) including those variants significantly associated with breast cancer risk, and also evaluated the contribution of PRS and clinical risk factors to breast cancer using receiver operating characteristic curve (AUC).

Results

Logistic regression results showed that nine individual SNPs were significantly associated with breast cancer risk after multiple testing. Among all SNPs, six variants, namely FGFR2 (rs2981582), HCN1 (rs981782), MAP3K1 (rs889312), TOX3 (rs3803662), ZNF365 (rs10822013), and RAD51B (rs3784099), were selected to create PRS model. A dose–response association was observed between breast cancer risk and the PRS. Women in the highest quartile of PRS had a significantly increased risk compared to women in the lowest quartile (odds ratio 2.26; 95% confidence interval 1.51–3.38). The AUC for a model which contained the PRS in addition to clinical risk factors was 66.52%, whereas that for a model which with established risk factors only was 63.38%.

Conclusions

Our data identified a genetic risk predictor of breast cancer in Taiwanese population and suggest that risk models including PRS and clinical risk factors are useful in discriminating women at high risk of breast cancer from those at low risk.

     

光子束和电子束在早期乳腺癌患者放疗瘤床加量计划的剂量学研究

Objective

The aim of our study was to assess and compare the potential dosimetric advantages and drawbacks of photon beams and electron beams as a boost for the tumor bed in superficial and deep seated early-stage breast cancer.

Methods

We planned CTs of 10 women with early breast cancer underwent breast conservative surgery were selected. Tumor bed was defined as superficial and deep with a cut of point 4 cm, those with less than 4 cm were defined as superficial tumors representing 4 patients and those with depth of 4 cm or more were classified as deep tumors representing 6 patients. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clips. The planning target volume (PTV) was the CTV plus margin 1 cm. A dose of 10 Gy in 2 Gy fractions was given concurrently at the last week of treatment. Organs at risk (OARs) were heart, lungs, contra-lateral breast and a 5 mm thick skin segment of the breast surface. Dose volume histograms were defined to quantify the quality of concurrent treatment plans assessing target coverage and sparing OARs. The following treatment techniques were assessed: photon beam with 3D-conformal technique and a single electron beam.

Results

For superficial tumors better coverage for CTV and PTV with good homogeneity with better CI was found for the 3D conformal radiotherapy (3DCRT) but with no significant planning objectives over electron beam. For deep tumors, the 3DCRT met the planning objectives for CTV, PTV with better coverage and fewer hot spots with better homogeneity and CI. For superficial tumors, OARs were spared by both techniques with better sparing for the electron beam where as for deep tumors also OARs were well spared by both techniques.

Conclusion

Boosting the tumor bed in earlystage breast cancer with optimized photon may be preferred to electron beam for both superficial and deep tumors. The OARs dose sparing effect may allow for a potential long-term toxicity risk reduction and better cosmesis.     

Intrathoracic latissimus dorsi muscle transposition: a reliable technique for prevention of bronchopleural fistula developing after extrapleural pneumonectomy and external beam radiotherapy in malignant pleural mesothelioma

Objective

Bronchopleural fistula (BPF) is a life threatening complication after pneumonectomy. Extra thoracic skeletal muscle transposition especially latissimus dorsi muscle flap (LDMF) had been used to prevent this complication. The aim of this study was to assess the effectiveness of LDMF in preventing BPF developing after extrapleural pneumonectomy (EPP) and external radiation therapy in malignant pleural mesothelioma (MPM).

Methods

Between May 1999 and Dec. 2008, 37 patients with MPM were operated upon by EPP using LDMF prophylactically to reinforce the bronchial stump, and then received external radiation therapy with or without postoperative chemotherapy.

Results

The mean age of all patients was 46.7 (range 26–57) years. Twenty five patients were males and 12 patients were females. Twenty three patients had MPM of the right side and 14 patients had MPM of the left side. The peri-operative mortality was 2.7% and only few flap related postoperative morbidity were reported in the form of minor seroma and subcutaneous surgical emphysema. The median follow up was 17 (range 9–43) months. All cases completed their postoperative external radiation therapy with no reported cases of early or late BPF.

Conclusion

Intrathoracic pedicled LDMF transposition is proved to be effective in prevention of BPF developing after EPP and external radiation therapy in MPM and it is advised to be a routine step in EPP in these cases and to use more sophisticated technique of postoperative external beam radiotherapy (3D conformal or IMRT) to minimize this complication.     

Low dose out-of-field radiotherapy,part 3: Qualitative and quantitative impact of scattered out-of-field radiation on MDA-MB-231 cell lines

Purpose

Patients who undergo external beam radiotherapy are at risk of developing second tumours due to scattered radiation outside the path of the primary beam. The aim of this study was to experimentally determine the in vitro radiobiological effects of scattered radiation in cells located outside the primary photon beam and to compare this to the effects that occur in cells inside the primary beam. The comparison was performed by assessing cell viability, DNA damage, and apoptosis.

Strahlentherapie des Prostatakarzinoms

Background

Prostate cancer is the seventh most common cause of death for men in Germany with a mortality rate of 10,1 %. External beam radiotherapy is the alternative primary therapy apart from surgery for patients with locally confined prostate cancer.

Results

The oncological result is linked to the overall dose used. The use of three-dimensional (3-D) conformal radiation therapy allows dose escalation with low side effects. In particular, intensity modulated radiotherapy (IMRT) enables complex dose distributions. As the prostate is a relatively mobile organ, image-guided radiation therapy is the key for a correct dose distribution, which can be achieved with nowadays tools fast and simple.

Conclusions

The new techniques are responsible for a safe dose escalation with low side effects. Patients with intermediate and high risk prostate cancer do profit from the combination of neoadjuvant/simultaneous and adjuvant hormone therapy.     

Breast cancer following radiotherapy for a hemangioma during childhood

Purpose

A cohort study was performed to investigate the carcinogenic effect of treatment of skin hemangioma with ionizing radiation in early childhood. This paper presents the incidence of breast cancer (BC) in this cohort and its association with radiotherapy.

Methods and materials

In an incidence study, 3,316 women treated for a skin hemangioma between 1941 and 1977 at the Institut Gustave-Roussy were included, among whom 2,697 had received radiotherapy. The mean age at first exposure was 0.7?years, and the mean absorbed dose to the breast was 70?mGy. Treatment reconstruction and the estimation of radiation doses delivered to the breast were obtained for 92% of the women who had received radiotherapy. External and internal analyses were performed.

Results

During an average follow-up of 35?years, a total of 17 women developed an invasive BC, compared to 7.5 expected in the French general population (SIR?=?2.3, 95% CI, 1.4?C3.5), and the absolute excess risk strongly increased with attained age. Compared to individuals with no radiotherapy, the risk of BC increased with increasing radiation dose with RRs of 3.2, 6.3, and 8.0 for dose categories of >0?C10, 10?C100, and >100?mGy, respectively; however, dose?Cresponse relationship was not significant.

Conclusion

This study confirms that radiation treatment performed in the past for hemangioma during childhood increases the risk of BC.     

Parotid gland sparing IMRT for head and neck cancer improves xerostomia related quality of life

Background

To compare two strategies of dynamic intensity modulated radiation therapy (dIMRT) with 3-dimensional conformal radiation therapy (3DCRT) in the setting of hypofractionated high-risk prostate cancer treatment.

Methods

3DCRT and dIMRT/Helical Tomotherapy(HT) planning with 10 CT datasets was undertaken to deliver 68 Gy in 25 fractions (prostate) and simultaneously delivering 45 Gy in 25 fractions (pelvic lymph node targets) in a single phase. The paradigms of pelvic vessel targeting (iliac vessels with margin are used to target pelvic nodes) and conformal normal tissue avoidance (treated soft tissues of the pelvis while limiting dose to identified pelvic critical structures) were assessed compared to 3DCRT controls. Both dIMRT/HT and 3DCRT solutions were compared to each other using repeated measures ANOVA and post-hoc paired t-tests.

Results

When compared to conformal pelvic vessel targeting, conformal normal tissue avoidance delivered more homogenous PTV delivery (2/2 t-test comparisons; p < 0.001), similar nodal coverage (8/8 t-test comparisons; p = ns), higher and more homogenous pelvic tissue dose (6/6 t-test comparisons; p < 0.03), at the cost of slightly higher critical structure dose (D_dose, 1–3 Gy over 5/10 dose points; p < 0.03). The dIMRT/HT approaches were superior to 3DCRT in sparing organs at risk (22/24 t-test comparisons; p < 0.05).

Conclusion

dIMRT/HT nodal and pelvic targeting is superior to 3DCRT in dose delivery and critical structure sparing in the setting of hypofractionation for high-risk prostate cancer. The pelvic targeting paradigm is a potential solution to deliver highly conformal pelvic radiation treatment in the setting of nodal location uncertainty in prostate cancer and other pelvic malignancies.     

A dosimetric analysis of respiration-gated radiotherapy in patients with stage III lung cancer

Background

The purpose of the study was the clinical implementation of a kV cone beam CT (CBCT) for setup correction in radiotherapy.

Patients and methods

For evaluation of the setup correction workflow, six tumor patients (lung cancer, sacral chordoma, head-and-neck and paraspinal tumor, and two prostate cancer patients) were selected. All patients were treated with fractionated stereotactic radiotherapy, five of them with intensity modulated radiotherapy (IMRT). For patient fixation, a scotch cast body frame or a vacuum pillow, each in combination with a scotch cast head mask, were used. The imaging equipment, consisting of an x-ray tube and a flat panel imager (FPI), was attached to a Siemens linear accelerator according to the in-line approach, i.e. with the imaging beam mounted opposite to the treatment beam sharing the same isocenter. For dose delivery, the treatment beam has to traverse the FPI which is mounted in the accessory tray below the multi-leaf collimator. For each patient, a predefined number of imaging projections over a range of at least 200 degrees were acquired. The fast reconstruction of the 3D-CBCT dataset was done with an implementation of the Feldkamp-David-Kress (FDK) algorithm. For the registration of the treatment planning CT with the acquired CBCT, an automatic mutual information matcher and manual matching was used.

Results and discussion

Bony landmarks were easily detected and the table shifts for correction of setup deviations could be automatically calculated in all cases. The image quality was sufficient for a visual comparison of the desired target point with the isocenter visible on the CBCT. Soft tissue contrast was problematic for the prostate of an obese patient, but good in the lung tumor case. The detected maximum setup deviation was 3 mm for patients fixated with the body frame, and 6 mm for patients positioned in the vacuum pillow. Using an action level of 2 mm translational error, a target point correction was carried out in 4 cases. The additional workload of the described workflow compared to a normal treatment fraction led to an extra time of about 10–12 minutes, which can be further reduced by streamlining the different steps.

Conclusion

The cone beam CT attached to a LINAC allows the acquisition of a CT scan of the patient in treatment position directly before treatment. Its image quality is sufficient for determining target point correction vectors. With the presented workflow, a target point correction within a clinically reasonable time frame is possible. This increases the treatment precision, and potentially the complex patient fixation techniques will become dispensable.     

Risk of mesothelioma following external beam radiotherapy for prostate cancer: a cohort analysis of SEER database

Purpose

To investigate the association between external beam radiotherapy (EBRT) for prostate cancer and mesothelioma using data from the US Surveillance, Epidemiology, and End Results (SEER) cancer registries.

Methods

We analyzed data from the SEER database (1973–2009). We compared EBRT versus no radiotherapy. Incidence rate ratios (IRR) and 95 % confidence intervals (95 % CI) of mesothelioma among prostate cancer patients were estimated with multilevel Poisson models adjusted by race, age, and calendar year. Confounding by asbestos was investigated using relative risk of mesothelioma in each case’s county of residence as a proxy for asbestos exposure.

Results

Four hundred and seventy-one mesothelioma cases (93.6 % pleural) occurred in 3,985,991 person-years. The IRR of mesothelioma was increased for subjects exposed to EBRT (1.28; 95 % CI 1.05, 1.55) compared to non-irradiated patients, and a population attributable fraction of 0.49 % (95 % CI 0.11, 0.81) was estimated. The IRR increased with latency period: 0–4 years, IRR 1.08 (95 % CI 0.81, 1.44); 5–9 years, IRR 1.31 (95 % CI 0.93, 1.85); ≥10 years, IRR 1.59 (95 % CI 1.05, 2.42). Despite the fairly strong evidence of association with EBRT, the population attributable rate of mesothelioma was modest—3.3 cases per 100,000 person-years. The cumulative incidence of mesothelioma attributable to EBRT was 4.0/100,000 over 5 years, 24.5/100,000 over 10 years, and 65.0/100,000 over 15 years.

Conclusions

Our study provides evidence that EBRT for prostate cancer is a small but detectable risk factor for mesothelioma. Patients should be advised of risk of radiation-induced second malignancies.     

Detailed dosimetric evaluation of intensity-modulated radiation therapy plans created for stage C prostate cancer based on a planning protocol

Background

Intensity-modulated radiation therapy (IMRT) has been employed as a precision radiation therapy with higher conformity to the target. Although clinical outcomes have been reported for many investigations, detailed treatment planning results have not been mentioned to date. The aim of this study was to evaluate the dose specifications of our IMRT treatment plans for locally advanced prostate cancer.

Methods

Seventy-seven clinically applied IMRT plans treated between September 2003 and December 2005, in which patients were irradiated with 78?Gy in the prone position, were retrospectively analyzed. Dosimetric data output from dose volume histograms were evaluated in detail.

Results

The mean dose?±?standard deviation, homogeneity index, and conformity index to the planning target volume (PTV) were 78.3?±?0.7?Gy (100.4?±?0.9%), 13.7?±?3.0, and 0.83?±?0.04, respectively. For the clinical target volume, the mean dose was 80.3?±?0.7?Gy (102.9?±?0.9%).The V40, V60, and V70?Gy of the rectal wall were 58.3?±?2.8, 29.6?±?2.7, and 15.2?±?3.0%, respectively. Planning difficulties were encountered in patients whose bowels were displaced downward, as constraints imposed by the bowel position altered the dose index of the PTV. In many cases, additional bowel optimization parameters were required to satisfy constraints for organs at risk. However, major deviation could be avoided by inverse planning with computer optimization.

Conclusion

IMRT allowed the creation of acceptable and practical treatment plans for locally advanced prostate cancer. Reports regarding detailed dosimetric evaluations are mandatory for interpreting clinical outcomes in the future.