To compare the outcomes of patients with intermediate risk prostate cancer (IR-PCa) treated with lowdose rate I-125 seed brachytherapy (LDR-BT) and targeted dose painting of a histologic dominant intra-epithelial lesion (DIL) to those without a DIL. Methods: 455 patients with IR-PCa were treated at a single center with intra-operatively planned LDR-BT, each following the same in-house dose constraints. Patients with a DIL on pathology had hot spots localized to that region but no specific contouring during the procedure. Results: 396 (87%) patients had a DIL. Baseline tumor characteristics and overall prostate dosimetry were similar between patients with and without DIL except the median number of biopsy cores taken: 10 (10-12) vs 12 (10-12) (p ¼ 0.002). 19 (5%) and 18 (5%) of patients with and 1 (2%) and 0 (0%) of those without DIL experienced CTCAE grade 2 and 3 toxicity respectively. Overall, toxicity grade did not significantly correlate with presence of DIL (p ¼ 0.10). Estimated 7-year freedom from biochemical failure (FFBF) was 84% (95% confidence interval: 79-89) and 70% (54-89) in patients with and without a DIL (log-rank p ¼ 0.315). In DIL patients, cox regression revealed location of DIL ("Base" vs "Apex" HR: 1.03; 1.00-1.06; p ¼ 0.03) and older age (70 vs 60 HR: 1.62; 1.06-2.49; p ¼ 0.03) was associated with poor FFBF. Conclusions: Targeting DIL through dose painting during intraoperatively planned LDR-BT provided no statistically significant change in FFBF. Patients with DILs in the prostate base had slightly lower FFBF despite DIL boost.
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306 Background: Palliative radiation therapy (RT) is offered to patients with cancer for symptom management. RT planning and delivery is resource intensive. Benefits may take weeks to develop. Palliative RT at the end of life may not be completed due to patient and disease factors. RT courses that are not completed may indicate a need for improved patient selection for RT and choice of RT prescription, minimizing the likelihood of delivering futile treatment. Methods: The FUTile Radiotherapy at End of life survey was implemented in the electronic RT workspace across Alberta in 2018. Radiation oncologists (ROs) were tasked with survey completion, at the time of palliative RT prescription approval, as part of their workflow on domains pertaining to patient and treatment decision-making. This survey data was linked to the cancer registry and date of death. Data association were examined among patients completing RT within 90 days of death for the accuracy of oncologist’s provided survival prognostication estimates, number of RT fractions prescribed, number of RT fractions completed, prescribing physician, including disease factors and treatment intent. Results were explored using descriptive statistics and tests of associations (STATA 11.1) Results: 1963 RT surveys were included in our analysis. Prescribing ROs overestimated patient survival 67% of the time, by a mean of 145 days, and underestimated survival 12% of the time by a mean of 109 days. Multi-fraction RT (1403 courses) was more frequently prescribed over single fraction (SF) RT (560 courses)(one-sample t-test, p≤0.001). SF treatments were more likely to be completed than MF treatments (RR = 10.3, 95% CI = [4.85, 21.7], p < 0.0001). Treatments were less likely to be completed when survival was overestimated by 6 or more months and were over twice as likely to be completed than when patient survival was underestimated (RR = 2.6, 95% CI = [1.04, 6.50], p = 0.04). Conclusions: Survival among end of life patients is overestimated by ROs prescribing palliative MF RT treatments.
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