RESUMO
Purpose: Intermediate- and high-risk prostate cancer patients undergoing combination external beam radiation therapy (EBRT) and low dose rate (LDR) brachytherapy have demonstrated increased genitourinary (GU) toxicity. We have previously demonstrated a method to combine EBRT and LDR dosimetry. In this work, we use this technique for a sample of patients with intermediate- and high-risk prostate cancer, correlate with clinical toxicity, and suggest preliminary summed organ-at-risk constraints for future investigation. Methods and Materials: Intensity modulated EBRT and 103Pd-based LDR treatment plans were combined for 138 patients using biological effective dose (BED) and deformable image registration. GU and gastrointestinal (GI) toxicity were compared with combined dosimetry for the urethra, bladder, and rectum. Differences between doses in each toxicity grade were assessed by analysis of variance (α = 0.05). Combined dosimetric constraints are proposed using the mean organ-at-risk dose, subtracting 1 standard deviation for a conservative recommendation. Results: The majority of our 138-patient cohort experienced grade 0 to 2 GU or GI toxicity. Six grade 3 toxicities were noted. Mean prostate BED D90 (± 1 standard deviation) was 165.5±11.1 Gy. Mean urethra BED D10 was 230.3±33.9 Gy. Mean bladder BED was 35.2±11.0 Gy. Mean rectum BED D2cc was 85.6±24.3 Gy. Significant dosimetric differences between toxicity grades were found for mean bladder BED, bladder D15, and rectum D50, but differences between individual means were not statistically significant. Given the low incidence of grade 3 GU and GI toxicity, we propose urethra D10 <200 Gy, rectum D2cc <60 Gy, and bladder D15 <45 Gy as preliminary dose constraints for combined modality therapy. Conclusions: We successfully applied our dose integration technique to a sample of patients with intermediate- and high-risk prostate cancer. Incidence of grade 3 toxicity was low, suggesting that combined doses observed in this study were safe. We suggest preliminary dose constraints as a conservative starting point to investigate and escalate prospectively in a future study.
RESUMO
PURPOSE: Medical students often complete clinical rotations at other institutions (away rotations). This study assesses the number of away rotations undertaken by radiation oncology residency applicants and their value from the applicants' perspective. METHODS AND MATERIALS: A survey was sent to applicants to a single radiation oncology program from 2015 to 2017. Questions addressed away rotation frequency, funding, motivations, barriers, and match results. A χ2 test was used to assess the correlation between number of away rotations and matching to an away program. Binary logistic regression was used to assess factors associated with undertaking >2 away rotations. RESULTS: The response rate was 39% (n = 194); 89% of respondents completed ≥1 away rotation (median, 2; interquartile range, 2-3), of whom 39% (n = 67) matched to an away program. The number of away rotations completed did not differ between those who did and did not match (P = .29). Furthermore, the number of away rotations did not correlate with matching at an away program (P = .40). Factors associated with completing more away rotations included male sex and high loan burden (P < .05). Away rotations were perceived as extremely important (71%), with interest in a specific program (44%) and obtaining letters of recommendation (31%) the most common reasons to pursue away rotations. Only 9% (n = 15) of applicants did away rotations because they had no home program. Funding sources included personal savings (29%), family support (26%), and loans (22%). If costs were inconsequential, 67 applicants (35%) noted they would do more away rotations. CONCLUSIONS: Away rotations are common and often result in students matching to an away program, although benefits of ≥2 away rotations appear limited and have associated costs. Limiting the number of away rotations in radiation oncology may decrease costs without sacrificing one's chances of matching.