Treating intermediate-risk prostate cancer with hypofractionated external beam radiotherapy alone.

Abstract

93 Background: A wide range of therapeutic alternatives is available for the treatment of intermediate-risk prostate cancer (IRPC). The use of hypofractionated external beam radiotherapy (HypoRT) in this group of patients appears to be an attractive option. Non-randomized institutional results have provided similar outcomes to conventional fractionation. For health-systems such as we have in Canada, where many patients live far, it significantly shortens treatment duration and impacts favorably in health costs. We report our results using HypoRT alone in IRPC. Methods: Between October/2002 and July/2009, 82 men with IRPC (T2b-T2c, or PSA 10–20 ng/dL, or GS=7) were treated with HypoRT, without any androgen deprivation. Ultrasound image guidance was used daily to confirm setup. The dose was 66 Gy in 22 daily fractions of 3 Gy (BED=79.4Gy/44) prescribed at the isocenter. PTV was the prostate (+/− 1cm seminal vesicles) with 7-mm margin in all directions. GI and GU toxicity were prospectively assessed every 4–6 months using the CTCAE v3 scoring system. Biochemical failure was defined as nadir PSA + 2 ng/dL. Results: 60% of patients had Gleason score 7; 43% had stage T2; median initial PSA=9 ng/ml; median age 71 years. With a median follow-up of 43 months (range: 7–89), only three patients (4%) have developed biochemical failure. All three showed metastatic disease few months after biochemical failure. Actuarial biochemical recurrence free survival (bNED) is 95.4%. There was no death related to prostate cancer. Three patients died from other causes without biochemical failure. The 5-year overall survival was 93%. At the last follow up visit, grade ≥ 2 late GI and GU toxicity rates were 2% and 7%, respectively. No grade 4 or 5 has occurred. Conclusions: Men with IRPC treated with 66Gy/22 fractions and without androgen deprivation have experienced excellent 5-year biochemical control rate with acceptable late toxicity. This regimen is very convenient because the duration of the treatment is half of the time used with conventional fractionation. Whether the addition of short-term androgen deprivation would further improve outcome remains unclear. No significant financial relationships to disclose.