A phamtom study: In vivo rectal dosimetry of high dose rate brachytherapy in cervical cancer.

The purpose of this study was to perform in-vivo dosimetry using a diode rectal dosimeter in phantom and compare the dose delivered to the rectum between the dose measured by the diode dosimeter and the dose calculated by the treatment planning system in cervical cancer. The PTW T9112 diode detector calibrations were performed to find the correction factor. Then the calibrated diode detector was used to measure the radiation dose received in the rectum area in the in-house pelvic phantom. An Iridium-192 source was loaded into the phantom with 7 Gy, the measurements were 3 times per treatment plan, with 15 total plans studied. The average cumulative charge (nC) of each plan was converted to the absorbed dose (mGy) for comparison with the treatment planning system. Finally, to test the hypothesis that an absorbed dose from the detector and the treatment planning system were not significantly different, dependent t-test statistical analysis was applied with p-value <0.05. For distance and direction correction factors, we found that the factors were approximately 1 at 5 cm and 180°. The percentage differences of radiation dose between the diode dosimeter and the treatment planning system were between -3.3 and 4.1%. Statistical analysis revealed that the doses from the detector and the treatment planning system were not statistically significant different. The comparison showed that the percent difference between diode dosimeter and treatment planning system was acceptable to perform the in vivo dosimetry in brachytherapy. Therefore, the diode detector may be a suitable candidate for a treatment verification system in cervical cancer brachytherapy to prevent the dose delivery errors that directly affect the prognosis and may cause complications for the patient.

Predictors for post-treatment biopsy outcomes after prostate stereotactic body radiotherapy.

PURPOSE: To investigate predictors associated with post-treatment biopsy outcomes after stereotactic body radiotherapy (SBRT) for localized prostate cancer. MATERIALS AND METHODS: 257 patients treated with prostate SBRT to dose levels of 32.5 Gy to >40 Gy in 5-6 fractions underwent a post-treatment biopsy performed approximately two years after treatment to evaluate local control status. 73 had% intermediate-risk disease (n = 187) and the remaining 17% (n = 43) and 10% (n = 27) had low-risk and high-risk disease, respectively. RESULTS: The incidence of positive, negative, and treatment-effect post-treatment biopsies were 15.6%, 57.6%, and 26.8%, respectively. The incidence of a positive biopsy according to dose was 37.5% (n = 9/24), 21.4% (n = 6/28), 19.4% (n = 6/31), and 10.9% (n = 19/174) for 32.5 Gy, 35 Gy, 37.5 Gy, and >40 Gy, respectively. In a multivariable model, patients treated with SBRT doses of <40 Gy and those with unfavorable-intermediate-risk or high-risk disease had higher likelihood of a positive post-treatment biopsy. A positive post-SBRT biopsy was associated with a significantly higher likelihood of subsequent PSA relapse at five years (Positive biopsy: 57%, 95% CI: 29-77% compared to negative biopsy: 7%, 95% CI: 3-14%; p < 0.001). CONCLUSION: Based on two-year post-SBRT biopsies, excellent tumor control was achieved when dose levels of 40 Gy or higher were used. Standard SBRT dose levels of 35-37.5 Gy were associated with a higher likelihood of a positive post-treatment biopsy. Two-year positive post-treatment biopsies pre-dated the development of PSA failure in the majority of patients.

Early Tolerance and Tumor Control Outcomes with High-dose Ultrahypofractionated Radiation Therapy for Prostate Cancer.

BACKGROUND: Studies using stereotactic body radiotherapy (SBRT) dose escalation in in low- and intermediate-risk prostate cancer patients have indicated favorable outcomes. OBJECTIVE: To evaluate tolerance and tumor control outcomes in low- and intermediate-risk prostate cancer patients treated with high-dose SBRT following our phase 1 trial. DESIGN, SETTING, AND PARTICIPANTS: A total of 551 patients with low- or intermediate-risk prostate cancer were treated with SBRT. INTERVENTION: Treatment with 37.5-40Gy SBRT in five fractions directed to the prostate and seminal vesicles. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Outcome measurements included acute toxicities (<3 mo after radiotherapy [RT]) and late toxicities (>3 mo after RT) and tumor control evaluation (prostate-specific antigen [PSA] levels at 3-6-mo intervals and post-treatment prostate biopsy at 2yr). RESULTS AND LIMITATIONS: Acute grade 2 gastrointestinal (GI) toxicities occurred in 1.8% of patients, and late grade 2 and 3 GI toxicities were observed in 3.4% and 0.4% of patients, respectively. Acute grade 2 genitourinary (GU) toxicities occurred in 10% of patients, and grade 3 acute GU toxicities were observed in 0.7% of patients. Late grade 2 and 3 GU toxicities were observed in 21.1% and 2.5% of patients, respectively. The use of a hydrogel rectal spacer was significantly associated with reduced late GI toxicity and lower odds of developing late GU toxicity. The median follow-up was 17 mo, and 53% of those with at least 2yr of follow-up (103/193) had a biopsy performed. The 5-yr cumulative incidence of PSA failure was 2.1%, and the incidence of a positive 2-yr treatment biopsy was 12%. Limitations to this report include its retrospective nature and short follow-up time. CONCLUSIONS: Favorable short-term outcomes were achieved with high-dose SBRT for low- and intermediate-risk disease. Severe late toxicities were observed and favorable tumor control was found. PATIENT SUMMARY: We utilized stereotactic body radiotherapy, a form of external beam radiotherapy that delivers highly targeted high-dose treatment to the prostate, to treat over 500 localized prostate cancer patients in five sessions over 1.5 wk. Treatments were well tolerated without significant urinary or rectal side effects. Nearly 90% of those who underwent biopsies after treatment did not demonstrate residual active disease.

Conventional versus hypofractionated postmastectomy radiotherapy: a report on long-term outcomes and late toxicity.

OBJECTIVE: We evaluated the long-term outcomes and late toxicity of conventional fractionated (CF) and hypofractionated (HF) postmastectomy radiotherapy (PMRT) in terms of locoregional recurrence-free survival (LRRFS), disease-free survival (DFS), overall survival (OS), and late toxicity. METHODS: A cohort of 1640 of breast cancer patients receiving PMRT between January 2004 and December 2014 were enrolled. Nine hundred eighty patients were treated with HF-PMRT: 2.65 Gy/fraction to a total of 42.4-53 Gy and 660 patients were treated with CF-PMRT: 2 Gy/fraction to a total of 50-60 Gy. RESULTS: The median follow-up time was 71.8 months (range 41.5-115.9 months). No significant difference was found in the rates of 5-year LRRFS, DFS, and OS of HF-PMRT vs CF-PMRT; 96% vs. 94% (p = 0.373), 70% vs. 72% (p = 0.849), and 73% vs. 74% (p = 0.463), respectively. We identified a cohort of 937 eligible breast cancer patients who could receive late toxicities assessment. With a median follow-up time of this patient cohort of 106.3 months (range 76-134 months), there was a significant higher incidence of grade 2 or more late skin (4% vs 1%) and subcutaneous (7% vs 2%) toxicity in patients treated with HF-PMRT vs CF-PMRT. Patients who received additional radiation boost were significantly higher in the HF-PMRT group. Grade 2 or more late RTOG/EORTC lung toxicity was significant lesser in HF-PMRT vs CF-PMRT (9% vs 16%). Grade 1 brachial plexopathy was also significant lesser in HF-PMRT vs CF-PMRT (2% vs 8%). Heart toxicity and lymphedema were similar in both groups. CONCLUSIONS: HF-PMRT is feasible to deliver with comparable long-term efficacy to CF-PMRT. HF-PMRT had higher grade 2 or more skin and subcutaneous toxicity but less lung and brachial plexus toxicity.

Early Tolerance Outcomes of Stereotactic Hypofractionated Accelerated Radiation Therapy Concomitant with Pelvic Node Irradiation in High-risk Prostate Cancer.

PURPOSE: This study aimed to evaluate the toxicity of prostate and pelvic lymph node stereotactic body radiation therapy (SBRT) for high-risk prostate cancer. METHODS AND MATERIALS: Twenty-three patients with high-risk or lymph node-positive prostate cancer were treated with SBRT that delivered 37.5 to 40 Gy in 5 fractions to the prostate and seminal vesicles, with concomitant treatment of the pelvic nodes to 25 Gy. In general, patients received neoadjuvant, concurrent, and adjuvant androgen deprivation therapy for a duration of 18 months. Toxicities were evaluated with the Common Terminology Criteria for Adverse Events, version 3.0. The median follow-up was 19 months (range, 3-48 months). RESULTS: Acute grade 1 gastrointestinal (GI) toxicities were noted in 2 patients (9.1%). No patient experienced acute grade ≥2 GI toxicity. Acute genitourinary (GU) grade 1, 2, and 3 toxicities were observed in 7 patients (31.8%), 8 patients (36.4%), and 1 patient (4.5%), respectively. Late grade 2 GI and GU toxicities were observed in 2 patients (9.1%) and 6 patients (27.3%), respectively. No late grade ≥3 GI toxicity was noted. Late grade ≥3 GU (hemorrhagic cystitis) was noted in 1 patient (4.5%), which responded to laser fulguration. CONCLUSIONS: SBRT with pelvic lymph node radiation therapy was feasible and well tolerated. The incidence of grade ≥3 GU and GI toxicities was uncommon. Continued follow-up will be required to determine the long-term safety and efficacy of this approach for high-risk patients.

A retrospective study comparing hypofractionated radiotherapy and conventional radiotherapy in postmastectomy breast cancer.

BACKGROUND: The conventional radiotherapy (CRT) in postmastectomy breast cancer is 1.8-2.0 Gy daily for 25 fractions, while hypofractionated radiotherapy (HFRT) delivered dose in fewer fractions with larger radiation intensity. The present study compares the efficacy of HFRT and CRT. MATERIAL AND METHOD: From 2004 to 2006, 215 patients were retrospectively reviewed. Sixty seven patients received CRT and 148 patients received HFRT (2.65 Gy in 16-18 fractions). Five-year locoregional control (LRC), disease free survival (DFS), overall survival (OS) and toxicities were analyzed. RESULTS: Median follow-up was 39 months. Five-year LRC was 86.6% in CRT and 85.8% in HFRT (p = 0.852). Five-year DFS was 62.7% and 69.6% (p = 0.136) in CRTand HFRT respectively. Patients who received HFRT had significant increase in 5-year OS (62.7% and 73.0% (p = 0.048). No difference of toxicities including changes in chest wall appearance, skin fibrosis, brachial plexopathy, arm edema, pulmonary fibrosis, rib fractures and cardiovascular events was found between two groups. CONCLUSION: HFRT is as effective as CRT in postmastectomy breast cancer.