High-dose external BEAM intensity-modulated radiotherapy (HD-IMRT) versus intensity-modulated radiotherapy plus HDR brachytherapy boost (LD-IMRT+HDR-B) dose escalation for intermediate- or high-risk prostate cancer

263 Background: To report early & late toxicity & biochemical outcome in a prospective series of 1,465 patients with intermediate- or high-risk clinically localized prostate cancer treated with either HD-IMRT or with LD-IMRT+HDR-B. Methods: Between 12/1999 and 10/2011, 1,465 patients (pts) with PSA›10, Gleason score›6 and/or T2b-T3 N0 M0 prostate cancer entered the study. Pts were prospectively assigned to one of the two treatment groups: 76 Gy HD-IMRT to the prostate in 38 fractions (group 1; 733 patients) or 46 Gy LD-IMRT followed by 16 Gy HDR-B given in 2 fractions of 8 Gy (group 2, 732 patients), limiting the maximum rectal dose to 85% of the prescribed dose. Both groups were well balanced taking into account patient’s as well as tumor’s characteristics. Toxicities were scored by the EORTC/RTOG morbidity grading scales. Special attention to local, regional or distant recurrence, survival, late effects, PSA and testosterone levels and quality of life was done. Results: All pts completed treatment. None pts included in the group 1 or 2 experienced grade 3 or more rectal toxicity. 94 pts of group 1 (12.8%) and 20 pts of group 2 (2.7%) developed grade 2 rectal toxicity (rectal bleeding or urgency). 49 pts in group 1 (6.7%) and 10 pts in group 2 (1.3%) developed grade 1 rectal bleeding (less than 2 times/week). With a mean follow-up of 112 months, the 10-year free-from-failure survival was 90.7% and 98.3% (p<0.001) in group 1 and 2 respectively; free-from-metastases survival 93.9% and 97.8% (p<0,002)for group 1 and 2 respectively; and cause-specific survival 90.1% and 98.2% (p<0.001). No complications grade 2-4 were seen in either group. Conclusions: IMRT + HDR brachytherapy boost was a safe and extremely effective method of escalating the dose to the prostate without increasing the risk of late effects. Acute as well as late rectal complications were significantly reduced. Control rates were significantly better in the HDR-boosted patients as expected by higher effective-dose. Brachytherapy boost treated patients had a significant longer survival.