Final results of the Montpellier prostate cancer intensity modulated radiotherapy pilot study.

Abstract

105 Background: Thirteen hundred prostate cancer patients have been treated with Intensity modulated radiotherapy (IMRT) since 2001. We present the final results of the pilot study concerning the first 373 patients with a median follow-up of 72.7 months (range 0 to 130). Methods: All patients received the entire treatment course to a prescribed total dose of 80 Gy. No pelvic irradiation was applied. Androgen ablation therapy was delivered for 6 months and 2 to 3 years in intermediate and high-risk patients, respectively (n=142, 38%). Prostate-specific antigen (PSA) failure was defined as nadir + 2. Toxicity was assessed according to the National Cancer Institute (NCI)/Common Terminology Criteria for Adverse Events (CTCAE) v3.0. Multivariate analysis using the Cox model was performed to assess factors that may impact on PSA relapse. Logistic regression was used to correlate clinical and physical parameters with grade 2 or higher gastro-intestinal and genitourinary toxicities. Results: Median age was 69 (range 40 to 81). One hundred thirty nine (37.3%), 167 (44.8%), and 67 (18%) patients were classified as low (group 1), intermediate (group 2), and high-risk (group 3) patients, respectively. The 5 year biochemical relapse-free survival (5y-biochemical recurrence-free survival [bRFS]) was 85.7% (95% CI, 0.81-0.89). For the three prognostic groups, 5y-bRFS was 91% (95% CI, 0.85-0.95), 82% (95% CI, 0.75-0.87), and 80% (95% CI, 0.67-0.88) for groups 1, 2, and 3, respectively. Multivariate analysis showed that the absence of hormonotherapy in the group 2 and the number of positive biopsies impact on PSA relapse (p=0.04, HR 1.8 and p=0.01, HR 2.13, respectively). The incidence of late grade 2 or higher rectal and urinary toxicities were 10.5% and 12.7%, respectively. The dose received by 50% (D50) of the rectum was the only factor significantly correlated with late grade 2 or higher rectal toxicities (p = 0.04). Similarly, the dose received by 50% (D50) of the bladder was the only factor significantly correlated with late grade 2 or higher bladder side-effects (p = 0.02). Conclusions: IMRT to 80 Gy can provide good to excellent carcinologic results and low late toxicity rates in all prostate cancer subgroups. Hormonotherapy combined to high dose IMRT seems to be a serious option to consider in intermediate-risk patients. Clinical trial information: ICM 2001-13.