We retrospectively analyzed BFFR in 362 patients with localized prostate cancer treated with IGRT. We compared BFFR with prospectively collected Radiation Therapy Oncology Group (RTOG) maximum acute gastrointestinal (GI) and genitourinary (GU) toxicity scores. Median follow-up for all patients was 58.3 months after total radiotherapy doses of 75.6-79.8 Gy.
Patients reporting RTOG acute GU or GI toxicity scores of 鈮? were considered 鈥渟ensitive鈥?(n = 141, 39%) and patients reporting scores <2 were considered 鈥渘onsensitive鈥?(n = 221, 61%). When calculating biochemical failure (BF) using the American Society for Therapeutic Radiology and Oncology definition at 5 years, 76%(CI 70-82%) of the 鈥渘onsensitive鈥?patients were failure free, compared with only 53%(CI 43-62%) of the 鈥渟ensitive鈥?patients (log-rank test, p < 0.0001). This difference was also observed using the Phoenix definition; 鈥渘onsensitive鈥?5-year BFFR was 81%(CI 74-86%) vs. 鈥渟ensitive鈥?BFFR was 68%(CI 58-76%; log-rank test p聽= 0.0012). The difference in BF between cohorts remained significant when controlled for radiation dose (75.6 vs. 79.8 Gy), prognostic stratification (T category, prostate-specific antigen, and Gleason score), and prostate volume.
This study unexpectedly shows that prostate cancer patients who develop 鈮rade 2 RTOG acute toxicity during radiotherapy are less likely to remain BFF at 5 years. These results deserve further study and, if validated in other large IGRT cohorts, additional models would be required to study interaction between normal tissue and tumor biology in prostate cancer patients.