Dosimetric Comparison Study of Proton Therapy Using Line Scanning versus Passive Scattering and Volumetric Modulated Arc Therapy for Localized Prostate Cancer.

BACKGROUND: The proton irradiation modality has transitioned from passive scattering (PS) to pencil beam scanning. Nevertheless, the documented outcomes predominantly rely on PS. METHODS: Thirty patients diagnosed with prostate cancer were selected to assess treatment planning across line scanning (LS), PS, and volumetric modulated arc therapy (VMAT). Dose constraints encompassed clinical target volume (CTV) D98 ≥ 73.0 Gy (RBE), rectal wall V65 < 17% and V40 < 35%, and bladder wall V65 < 25% and V40 < 50%. The CTV, rectal wall, and bladder wall dose volumes were calculated and evaluated using the Freidman test. RESULTS: The LS technique adhered to all dose limitations. For the rectal and bladder walls, 10 (33.3%) and 21 (70.0%) patients in the PS method and 5 (16.7%) and 1 (3.3%) patients in VMAT, respectively, failed to meet the stipulated requirements. The wide ranges of the rectal and bladder wall volumes (V10-70) were lower with LS than with PS and VMAT. LS outperformed VMAT across all dose-volume rectal and bladder wall indices. CONCLUSION: The LS method demonstrated a reduction in rectal and bladder doses relative to PS and VMAT, thereby suggesting the potential for mitigating toxicities.

Proton Therapy for Localized Prostate Cancer: Long-Term Results From a Single-Center Experience.

PURPOSE: Although proton therapy is controversial, it has been used to treat localized prostate cancer over the past 2 decades. The purpose of this study is to examine the long-term efficacy and toxicity of proton therapy for localized prostate cancer. METHODS AND MATERIALS: This was a retrospective observational study of 2021 patients from 2003 to 2014 at a single institution. Patients were classified using the risk groups defined by the National Comprehensive Cancer Network guidelines, version 4.2019. Ninety-eight percent of the patients received 74 Gy (relative biological effectiveness) in 37 fractions. Fifty-one and 6% of the patients received neoadjuvant and adjuvant androgen deprivation therapy, respectively. The outcomes were the time of freedom from biochemical relapse and the time to late toxicity by the National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0. The outcomes were estimated using the Kaplan-Meier method and were analyzed using multivariable Cox proportional hazards models. RESULTS: The median follow-up period was 84 months (interquartile range, 60-110). The 5- and 10-year freedom from biochemical relapse rates were 100% and 100%, 99% and 88%, 93% and 86%, 90% and 79%, 88% and 68%, and 76% and 63% for the very low, low, favorable intermediate, unfavorable intermediate, high, and very high-risk groups, respectively. Patients with higher risk experienced biochemical relapse after shorter periods. The 5-year rates of grade 2 or higher late genitourinary and gastrointestinal toxicity were 2.2% and 4.0%, respectively. The results of multivariable analyses indicate that younger patients more often experienced biochemical relapse. CONCLUSIONS: This study demonstrates the favorable biochemical controls of proton therapy even in advanced localized prostate cancer patients with a low incidence of late toxicities, supporting the feasibility of conducting prospective clinical trials. The risk groups defined by the National Comprehensive Cancer Network guidelines, version 4.2019, are useful to classify patients with localized prostate cancer. Our findings might suggest the necessity to develop a treatment strategy that accounts for the patient's age.

Evaluation of the urethral α/ß ratio and tissue repair half-time for iodine-125 prostate brachytherapy with or without supplemental external beam radiotherapy.

PURPOSE: To assess the correlation between postimplant dosimetric quantifiers and the genitourinary (GU) toxicity of low-dose rate brachytherapy for prostate cancer. METHODS AND MATERIALS: The minimum urethral dose (UD10, 30, and 90) and the percent volume of the urethra receiving the prescription dose (V100, V150) were calculated from the postimplant dose-volume histograms of 182 patients. We then calculated various urethral biologically equivalent doses (uBEDs) using different values of the α/ß ratio and tissue repair half-time (t1/2) and examined the correlations with GU toxicity. RESULTS: Common dosimetric quantifiers, such as UD90 (brachytherapy) + UD50 (external beam radiotherapy), showed no correlation with Grade ≥ 2 GU toxicity. There was a significant correlation between Grade ≥2 GU toxicity and uBED when the α/ß value was 0.5 or 1 Gy and t1/2 was 0.5-2.5 h. An uBED (α/ß = 1.0, t1/2 = 0.5) had the largest hazard ratio for GU toxicity, and it was also significantly correlated with Grade ≥ 2 GU toxicity according to multivariate analysis. CONCLUSIONS: We observed a significant correlation of uBED with GU toxicity when α/ß was 0.5 or 1.0 Gy and t1/2 was 0.5-2.5 h. As the simple formula we used has not been verified in basic experiments, more data are needed to validate our results.

Proton Beam Therapy for Locally Recurrent Parotid Gland Cancer.

The aim of this study was to evaluate the efficacy and safety of proton beam therapy for patients with locally recurrent parotid cancer. Between 2009 and 2012, ten patients with locally recurrent parotid gland cancer were treated with proton beam therapy (70.2 Gy equivalents in 32 fractions) with or without intra-arterial infusion chemotherapy of cisplatin (50 mg/body/week, for a total of 5-8 weeks). The median follow-up was 24 months (range 10-49 months). The 1-year overall survival and local control rates were 80 %, and the 3-year overall survival and local control rates were 60 %. None of the patients experienced grade 3-5 toxicities in the treatment or the follow-up periods. These findings suggest that proton beam therapy could be applied effectively and safely for patients with locally recurrent parotid gland cancer.

Re-irradiation using proton beam therapy combined with weekly intra-arterial chemotherapy for recurrent oral cancer.

AIM: The purpose of this study was to clarify the efficacy and toxicities of re-irradiation using proton beam therapy combined with weekly intra-arterial chemotherapy for recurrent oral cancer. METHODS: Between October 2009 and July 2014, 34 patients who had recurrent oral cancer were treated by proton beam therapy combined with intra-arterial infusion chemotherapy at the Southern Tohoku Proton Therapy Center, Japan. RESULTS: For all patients, the median follow-up was 25 months (range, 3-77 months). After treatment, 22 patients (65%) achieved a complete response, and 12 patients (35%) achieved a partial response at the primary tumor site. One-year and 2-year overall survival (OS) rates were 62% and 42%, respectively. One-year and 2-year LC rates were 77% and 60%, respectively. No treatment-related deaths were observed during the treatment and follow-up periods. CONCLUSION: Re-irradiation using proton beam therapy combined with weekly intra-arterial chemotherapy improved OS and local control rates compared with other treatment modalities and could become a new treatment modality for patients with recurrent oral cancer.

The clinical results of proton beam therapy in patients with idiopathic pulmonary fibrosis: a single center experience.

BACKGROUND: The purpose of this study is to retrospectively evaluate the incidence of lung toxicities after proton beam therapy (PBT) in patients with idiopathic pulmonary fibrosis (IPF). METHODS: Patients diagnosed with primary lung cancer or lung metastasis who were treated with PBT between January 2009 and May 2015 were recruited from our database retrospectively. Cases of pneumonitis (excluding infection-related pneumonitis) were evaluated using the Common Terminology Criteria for Adverse Events version 4.0, and the Fletcher-Hugh-Jones classification of respiratory status was used to evaluate pretreatment and posttreatment respiratory function. RESULTS: Sixteen IPF patients received PBT for lung tumors, 15 received PBT for primary lung cancer, and one patient received PBT for metastasis from lung cancer. The cohort was composed of 14 men and 2 women, with a median age of 76 years (range: 63-89 years). The median follow-up time was 12 months (range: 4-39 months). The median dose of PBT was 80.0 Gy relative biological dose effectiveness (RBE) (range: 66.0-86.4 Gy [RBE]). The cumulative incidence of pneumonitis was 19.8 % (95 % confidence interval [CI]: 0-40.0 %), including one case of grade 5 pneumonitis. Reduced respiratory function was observed after PBT in seven patients, including one patient with pleural dissemination; five of these patients required home oxygen therapy. CONCLUSIONS: This study suggests that PBT can be performed more safely in IPF patients than surgery or X-ray irradiation. Although PBT has become a treatment choice for lung tumors of patients with IPF, the adverse events warrant serious attention.

Dosemetric Parameters Predictive of Rib Fractures after Proton Beam Therapy for Early-Stage Lung Cancer.

Proton beam therapy (PBT) is the preferred modality for early-stage lung cancer. Compared with X-ray therapy, PBT offers good dose concentration as revealed by the characteristics of the Bragg peak. Rib fractures (RFs) after PBT lead to decreased quality of life for patients. However, the incidence of and the risk factors for RFs after PBT have not yet been clarified. We therefore explored the relationship between irradiated rib volume and RFs after PBT for early-stage lung cancer. The purpose of this study was to investigate the incidence and the risk factors for RFs following PBT for early-stage lung cancer. We investigated 52 early-stage lung cancer patients and analyzed a total of 215 irradiated ribs after PBT. Grade 2 RFs occurred in 12 patients (20 ribs); these RFs were symptomatic without displacement. No patient experienced more severe RFs. The median time to grade 2 RFs development was 17 months (range: 9-29 months). The three-year incidence of grade 2 RFs was 30.2%. According to the analysis comparing radiation dose and rib volume using receiver operating characteristic curves, we demonstrated that the volume of ribs receiving more than 120 Gy3 (relative biological effectiveness (RBE)) was more than 3.7 cm(3) at an area under the curve of 0.81, which increased the incidence of RFs after PBT (P < 0.001). In this study, RFs were frequently observed following PBT for early-stage lung cancer. We demonstrated that the volume of ribs receiving more than 120 Gy3 (RBE) was the most significant parameter for predicting RFs.

Retrograde intra-arterial chemotherapy and daily concurrent proton beam therapy for recurrent oral cavity squamous cell carcinoma: Analysis of therapeutic results in 46 cases.

BACKGROUND: The purpose of this study was to evaluate the efficacy and toxicities of proton beam therapy combined with intra-arterial infusion chemotherapy via superficial temporal and occipital arteries for recurrent oral cavity squamous cell carcinoma (SCC). METHODS: Between October 2009 and June 2013, 46 patients with recurrent oral cavity SCC were treated by proton beam therapy combined with intra-arterial infusion chemotherapy of cisplatin (CDDP) and docetaxel. Treatment consisted of proton beam therapy (28.6-74.8 GyE in 13-34 fractions) and intra-arterial infusion chemotherapy (CDDP, 30-50 mg/body/week; docetaxel, 5-25 mg/body/week). RESULTS: One-year and 2-year overall survival (OS) rates were 65% and 46%, respectively. One-year and 2-year local control rates were 81% and 70%, respectively. CONCLUSION: These findings suggest that proton beam therapy combined with intra-arterial infusion chemotherapy could be applied effectively and safely for patients with recurrent oral cavity SCC. © 2016 Wiley Periodicals, Inc. Head Neck 38:1145-1151, 2016.

Clinical Outcomes and Prognostic Factors of High-Dose Proton Beam Therapy for Peripheral Stage I Non-Small-Cell Lung Cancer.

BACKGROUND: The efficacy, toxicity, and prognostic factors of high-dose proton beam therapy (PBT) for peripheral stage I non-small-cell lung cancer were assessed in this retrospective study. MATERIALS AND METHODS: Fifty patients with peripheral stage I non-small-cell lung cancer, two of whom had heterochronic multiple lung cancers, underwent high-dose PBT between January 2009 and September 2014. The relative biological effectiveness of the proton beam was defined as 1.1. The beam energy and spread-out Bragg peak were fine-tuned for the 90% isodose volume of the prescribed dosage to encompass the planning target volume. The cumulative survival curves were calculated using the Kaplan-Meier method. Treatment toxicities were evaluated using version 4 of the Common Terminology Criteria for Adverse Events, version 4. RESULTS: The study included 35 males and 15 females with a median age of 72.5 years. The median follow-up period was 22.8 months. The clinical stage was IA in 44 (85%) and IB in eight (15%) tumors. The total dose of PBT was 66 GyE in 10 fractions in all tumors. Three-year overall survival rate among all patients was 87.9% (95% confidence interval [CI], 94.8%-73.2%). Forty-five patients were alive, and 5 were dead. Three-year local control and progression-free survival rates were 95.7% (95% CI, 98.9%-83.8%) and 76.3% (95% CI, 86.9%-59.3%), respectively. Only one patient experienced Grade 2 pneumonitis. CONCLUSION: High-dose PBT may be an effective and safe treatment option for patients with stage I non-small-cell lung cancer.

Preliminary treatment results of proton beam therapy with chemoradiotherapy for stage I-III esophageal cancer.

The effect of proton beam therapy (PBT) on various cancers is controversial. We aimed to evaluate the efficacy and safety of PBT with alternating chemoradiotherapy (ACRT) for patients with stage I-III esophageal cancer. Two cycles of systemic chemotherapy with a continuous infusion of 5-fluorouracil (5-FU) on days 1-5 and a 5h infusion of nedaplatin (NDP) on day 6 were accompanied by thoracic irradiation using X-ray therapy and PBT. During the first half of the treatment, X-rays were delivered to the prophylactic area. During the second half of the treatment, proton beams were used to irradiate the involved field. To reduce the dose of cardiac irradiation, proton beams were delivered with posterior and posterior oblique angles. Between January 2009 and December 2012, 47 patients were enrolled in this study. The median follow-up duration was 29 months for all patients and 40 months for survivors. The 3 year overall survival rate, progression-free survival rate, and local control rate were 59.2%, 56.3%, and 69.8%, respectively. With respect to grade 3-4 late toxicities, there were no pleural or pericardial effusions, but two patients (4.3%) had esophageal stenosis, one patient (2.1%) had fistula, and two patients (4.3%) developed radiation pneumonitis. PBT with ACRT might have the potential to reduce the risk of cardiac damage and might become one of the primary methods of esophageal cancer treatment.

Preliminary results of proton beam therapy combined with weekly cisplatin intra-arterial infusion via a superficial temporal artery for treatment of maxillary sinus carcinoma.

OBJECTIVE: This study aimed to evaluate the efficacy and toxicity of proton beam therapy combined with cisplatin intra-arterial infusion via a superficial temporal artery as treatment for maxillary sinus carcinoma. METHODS: Twenty-six patients with confirmed maxillary sinus carcinoma were enrolled in this study from May 2009 to April 2011. Patients underwent proton beam therapy and intra-arterial infusion chemotherapy with cisplatin. RESULTS: The median total dose was 70.4 GyE per 32 fractions, and the median dose of cisplatin was 300 mg/body for six cycles of intra-arterial infusion. The 3-year overall survival rate was 58% for all patients (n = 26), 58% for patients with stage T4 disease (n = 12), 57% for patients with

Treatment results of alternating chemoradiotherapy followed by proton beam therapy boost combined with intra-arterial infusion chemotherapy for stage III-IVB tongue cancer.

PURPOSE: Proton beam therapy (PBT), compared with conventional radiotherapy, can deliver high-dose radiation to a tumor, while minimizing doses delivered to surrounding normal tissues. The better dose distribution of PBT may contribute to the improvement in local control rate and reduction in late adverse events. We evaluated therapeutic results and toxicities of PBT combined with selective intra-arterial infusion chemotherapy (PBT-IACT) in patients with stage III-IVB squamous cell carcinoma of the tongue. MATERIALS AND METHODS: After 2 systemic chemotherapy courses and whole-neck irradiation (36 Gy in 20 fractions), we administered concurrent chemoradiotherapy comprising PBT for the primary tumor [28.6-33 Gy(RBE) in 13-15 fractions] and for the metastatic neck lymph node [33-39.6 Gy(RBE) in 15-18 fractions] with weekly retrograde intra-arterial chemotherapy by continuous infusion of cisplatin with sodium thiosulfate. RESULTS: Between February 2009 and September 2012, 33 patients were enrolled. The median follow-up duration was 43 months. The 3-year overall survival, progression-free survival, local control rate, and regional control rate for the neck were 87.0, 74.1, 86.6, and 83.9 %, respectively. Major acute toxicities >grade 3 included mucositis in 26 cases (79 %), neutropenia in 17 cases (51 %), and dermatitis in 11 cases (33 %). Late grade 2 osteoradionecrosis was observed in 1 case (3 %). CONCLUSIONS: PBT-IACT for stage III-IVB tongue cancer has an acceptable toxicity profile and showed good treatment results. This protocol should be considered as a treatment option for locally advanced tongue cancer.

Prospective Trial of Stereotactic Body Radiation Therapy for Both Operable and Inoperable T1N0M0 Non-Small Cell Lung Cancer: Japan Clinical Oncology Group Study JCOG0403.

PURPOSE: To evaluate, in Japan Clinical Oncology Group study 0403, the safety and efficacy of stereotactic body radiation therapy (SBRT) in patients with T1N0M0 non-small cell lung cancer (NSCLC). METHODS AND MATERIALS: Eligibility criteria included histologically or cytologically proven NSCLC, clinical T1N0M0. Prescribed dose was 48 Gy at the isocenter in 4 fractions. The primary endpoint was the percent (%) 3-year overall survival. The threshold % 3-year survival to be rejected was set at 35% for inoperable patients, whereas the expected % 3-year survival was 80% for operable patients. RESULTS: Between July 2004 and November 2008, 169 patients from 15 institutions were registered. One hundred inoperable and 64 operable patients (total 164) were eligible. Patients' characteristics were 122 male, 47 female; median age 78 years (range, 50-91 years); adenocarcinomas, 90; squamous cell carcinomas, 61; others, 18. Of the 100 inoperable patients, the % 3-year OS was 59.9% (95% confidence interval 49.6%-68.8%). Grade 3 and 4 toxicities were observed in 10 and 2 patients, respectively. No grade 5 toxicity was observed. Of the 64 operable patients, the % 3-year OS was 76.5% (95% confidence interval 64.0%-85.1%). Grade 3 toxicities were observed in 5 patients. No grade 4 and 5 toxicities were observed. CONCLUSIONS: Stereotactic body radiation therapy for stage I NSCLC is effective, with low incidences of severe toxicity. This treatment can be considered a standard treatment for inoperable stage I NSCLC. This treatment is promising as an alternative to surgery for operable stage I NSCLC.

Analysis of Prostate Deformation during a Course of Radiation Therapy for Prostate Cancer.

PURPOSE: Accurate analysis of the correlation between deformation of the prostate and displacement of its center of gravity (CoG) is important for efficient radiation therapy for prostate cancer. In this study, we addressed this problem by introducing a new analysis approach. METHOD: A planning computed tomography (CT) scan and 7 repeat cone-beam CT scans during the course of treatment were obtained for 19 prostate cancer patients who underwent three-dimensional conformal radiation therapy. A single observer contoured the prostate gland only. To evaluate the local deformation of the prostate, it was divided into 12 manually defined segments. Prostate deformation was calculated using in-house developed software. The correlation between the displacement of the CoG and the local deformation of the prostate was evaluated using multiple regression analysis. RESULTS: The mean value and standard deviation (SD) of the prostate deformation were 0.6 mm and 1.7 mm, respectively. For the majority of the patients, the local SD of the deformation was slightly lager in the superior and inferior segments. Multiple regression analysis revealed that the anterior-posterior displacement of the CoG of the prostate had a highly significant correlation with the deformations in the middle-anterior (p < 0.01) and middle-posterior (p < 0.01) segments of the prostate surface (R2 = 0.84). However, there was no significant correlation between the displacement of the CoG and the deformation of the prostate surface in other segments. CONCLUSION: Anterior-posterior displacement of the CoG of the prostate is highly correlated with deformation in its middle-anterior and posterior segments. In the radiation therapy for prostate cancer, it is necessary to optimize the internal margin for every position of the prostate measured using image-guided radiation therapy.

High-dose proton beam therapy for stage I non-small cell lung cancer: Clinical outcomes and prognostic factors.

BACKGROUND: Evidence has suggested that radiation therapy with a lower dose per fraction may be a reasonable option for the treatment of centrally located non-small cell lung cancer (NSCLC). The aim of this study was to evaluate the safety and efficacy of two proton beam therapy (PBT) protocols for stage I NSCLC and to determine prognostic factors. MATERIAL AND METHODS: This study included patients clinically diagnosed with stage I NSCLC. Based on the location of the tumor, one of the two PBT protocols was administered. Patients with peripherally located tumors were given 66 Gy relative biological dose effectiveness (RBE) over 10 fractions (Protocol A) while patients with centrally located tumors were given 80 Gy (RBE) over 25 fractions (Protocol B). RESULTS: Between January 2009 and May 2012, 56 eligible patients were enrolled (protocol A: 32 patients; protocol B: 24 patients). The three-year overall survival (OS), progression-free survival (PFS), and local control (LC) rates were 81.3% [95% confidence interval (CI) 75.9-86.7%], 73.4% (95% CI 67.2-79.6%), and 96.0% (95% CI 93.2-98.8%), respectively. There were no significant differences in outcomes between the two protocols. Late grade 2 and 3 pulmonary toxicities were observed in nine patients (13.4%) and one patient (1.5%), respectively; no grade 4 or 5 toxicities were observed. Sex, age, performance status, T-stage, operability, and tumor pathology were not associated with OS and PFS. Only maximum standardized uptake value (SUVmax; <5 vs. ≥5) was identified as a significant prognostic factor for OS and PFS. CONCLUSION: Both high-dose PBT protocols achieved high LC rates with tolerable toxicities in stage I NSCLC patients, and SUVmax was a significant prognostic factor.

Results and DVH analysis of late rectal bleeding in patients treated with 3D-CRT or IMRT for localized prostate cancer.

In patients undergoing radiotherapy for localized prostate cancer, dose-volume histograms and clinical variables were examined to search for correlations between radiation treatment planning parameters and late rectal bleeding. We analyzed 129 patients with localized prostate cancer who were managed from 2002 to 2010 at our institution. They were treated with 3D conformal radiation therapy (3D-CRT, 70 Gy/35 fractions, 55 patients) or intensity-modulated radiation therapy (IMRT, 76 Gy/38 fractions, 74 patients). All radiation treatment plans were retrospectively reconstructed, dose-volume histograms of the rectum were generated, and the doses delivered to the rectum were calculated. Time to rectal bleeding ranged from 9-53 months, with a median of 18.7 months. Of the 129 patients, 33 patients had Grade 1 bleeding and were treated with steroid suppositories, while 25 patients with Grade 2 bleeding received argon plasma laser coagulation therapy (APC). Three patients with Grade 3 bleeding required both APC and blood transfusion. The 5-year incidence rate of Grade 2 or 3 rectal bleeding was 21.8% for the 3D-CRT group and 21.6% for the IMRT group. Univariate analysis showed significant differences in the average values from V65 to V10 between Grades 0-1 and Grades 2-3. Multivariate analysis demonstrated that patients with V65 ≥ 17% had a significantly increased risk (P = 0.032) of Grade 2 or 3 rectal bleeding. Of the 28 patients of Grade 2 or 3 rectal bleeding, 17 patients (60.7%) were cured by a single session of APC, while the other 11 patients required two sessions. Thus, none of the patients had any further rectal bleeding after the second APC session.

Clinical results of proton beam therapy for twenty older patients with esophageal cancer.

BACKGROUND: In an aging society, increasing number of older patients are diagnosed with esophageal cancer. The purpose of this study was to assess the clinical efficacy and safety of proton beam therapy for older patients with esophageal cancer. PATIENTS AND METHODS: Older patients (age: ≥ 65 years) newly diagnosed with esophageal cancer between January 2009 and June 2013 were enrolled in this study. All patients underwent either proton beam therapy alone or proton beam therapy with initial X-ray irradiation. Toxicities were evaluated using the Common Terminology Criteria for Adverse Events version 4.0. RESULTS: Twenty patients were eligible for this study and all completed the treatment. The median age was 78 years (range: 65-89 years) and the median follow-up time was 26.5 months (range: 6-62 months). Seven patients had lymph node metastases and 10 had stage II/III cancer. The median dose of proton beam therapy was 72.6 Gy relative biological dose effectiveness (RBE) (range: 66-74.8 Gy [RBE]) for proton beam therapy alone and 33 Gy (RBE) (range: 30.8-39.6 Gy [RBE]; total dose range: 66.8-75.6 Gy [RBE]) for proton beam therapy with initial X-ray irradiation. The 2-year overall survival rate was 81.8% (95% confidence interval [CI]: 62.4%-100%), and the 2-year local control rate was 89.4% (95% CI: 75.5%-100%). Grade 2 or 3 toxicities occurred in some cases; however, no grade 4 or 5 toxicity was observed. CONCLUSIONS: High-dose (66-75.6 Gy [RBE]) proton beam therapy without chemotherapy was an efficacious and safe treatment for older patients with esophageal cancer.

Strength estimation of a moving 125Iodine source during implantation in brachytherapy: application to linked sources.

This study sought to demonstrate the feasibility of estimating the source strength during implantation in brachytherapy. The requirement for measuring the strengths of the linked sources was investigated. The utilized sources were (125)I with air kerma strengths of 8.38-8.63 U (µGy m(2) h(-1)). Measurements were performed with a plastic scintillator (80 mm × 50 mm × 20 mm in thickness). For a source-to-source distance of 10.5 mm and at source speeds of up to 200 mm s(-1), a counting time of 10 ms and a detector-to-needle distance of 5 mm were found to be the appropriate measurement conditions. The combined standard uncertainty (CSU) with the coverage factor of 1 (k = 1) was ∼15% when using a grid to decrease the interference by the neighboring sources. Without the grid, the CSU (k = 1) was ∼5%, and an 8% overestimation due to the neighboring sources was found to potentially cause additional uncertainty. In order to improve the accuracy in estimating source strength, it is recommended that the measurment conditions should be optimized by considering the tradeoff between the overestimation due to the neighboring sources and the intensity of the measured value, which influences the random error.

Clinical outcomes and toxicity of proton beam therapy for advanced cholangiocarcinoma.

BACKGROUND: We examined the efficacy and toxicity of proton beam therapy (PBT) for treating advanced cholangiocarcinoma. METHODS: The clinical data and outcomes of 28 cholangiocarcinoma patients treated with PBT between January 2009 and August 2011 were retrospectively examined. The Kaplan-Meier method was used to estimate overall survival (OS), progression-free survival (PFS), and local control (LC) rates, and the log-rank test to analyze the effects of different clinical and treatment variables on survival. Acute and late toxicities were assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. RESULTS: The median age of the 17 male and 11 female patients was 71 years (range, 41 to 84 years; intrahepatic/peripheral cholangiocarcinoma, n = 6; hilar cholangiocarcinoma/Klatskin tumor, n = 6; distal extrahepatic cholangiocarcinoma, n = 3; gallbladder cancer, n = 3; local or lymph node recurrence, n = 10; size, 20-175 mm; median 52 mm). The median radiation dose was 68.2 Gy (relative biological effectiveness [RBE]) (range, 50.6 to 80 Gy (RBE)), with delivery of fractions of 2.0 to 3.2 Gy (RBE) daily. The median follow-up duration was 12 months (range, 3 to 29 months). Fifteen patients underwent chemotherapy and 8 patients, palliative biliary stent placement prior to PBT. OS, PFS, and LC rates at 1 year were 49.0%, 29.5%, and 67.7%, respectively. LC was achieved in 6 patients, and was better in patients administered a biologically equivalent dose of 10 (BED10) > 70 Gy compared to those administered < 70 Gy (83.1% vs. 22.2%, respectively, at 1 year). The variables of tumor size and performance status were associated with survival. Late gastrointestinal toxicities grade 2 or greater were observed in 7 patients <12 months after PBT. Cholangitis was observed in 11 patients and 3 patients required stent replacement. CONCLUSIONS: Relatively high LC rates after PBT for advanced cholangiocarcinoma can be achieved by delivery of a BED10 > 70 Gy. Gastrointestinal toxicities, especially those of the duodenum, are dose-limiting toxicities associated with PBT, and early metastatic progression remains a treatment obstacle.

A dosimetry method for low dose rate brachytherapy by EGS5 combined with regression to reflect source strength shortage.

The post-implantation dosimetry for brachytherapy using Monte Carlo calculation by EGS5 code combined with the source strength regression was investigated with respect to its validity. In this method, the source strength for the EGS5 calculation was adjusted with the regression, so that the calculation would reproduce the dose monitored with the glass rod dosimeters (GRDs) on a water phantom. The experiments were performed, simulating the case where one of two (125)I sources of Oncoseed 6711 was lacking strength by 4-48%. As a result, the calculation without regression was in agreement with the GRD measurement within 26-62%. In this case, the shortage in strength of a source was neglected. By the regression, in order to reflect the strength shortage, the agreement was improved up to 17-24%. This agreement was also comparable with accuracy of the dose calculation for single source geometry reported previously. These results suggest the validity of the dosimetry method proposed in this study.