Conformal radiotherapy to 76 Gy in localized prostate cancer. Therapeutic modalities and preliminary results

Purpose: to describe therapeutic modalities for localized prostate cancer treated by conformal radiation to 76 Gy with or without androgen ablation. To evaluate the preliminary results in terms of survival, biological control and toxicity. Patients and method: between January 1998 and June 2001, 321 patients with localized prostate cancer were irradiated at Institut Curie. Tumors were stratified into the three Memorial Sloan-Kettering Cancer Center prognostic groups (1998) for analysis: favorable risk group (F.G.) 23%, intermediate risk group (I.G.) 36.5%, unfavorable risk group (U.G.) 40.5%. Androgen deprivation, mainly neo-adjuvant, less or equal to one year was prescribed to 93.8% of patients (72.6% less or equal to six months). Planning target volume prescription doses were: prostate: 76 Gy, seminal vesicles: 56 to 76 Gy, and pelvic lymph nodes: 44 Gy to 16.8% of patients. Results: the five-year actuarial overall survival was 94% (95% I.C.: 90-97%). The median post-therapeutic follow-up was 36 months (nine to 60 months). The 48-month actuarial rates of biochemical control for the three prognostic groups were statistically different according to both the American Society for Therapeutic Radiology and Oncology consensus (A.S.T.R.O. 1997) and the Fox Chase Cancer Center definitions of biochemical failure (F.C.C.C. 2000) with respectively 87 and 94% for F.G., 78 and 84% for I.G., 54 and 58% for U.G. (P < 10-6 and P < 10-8). At time of our analysis, late post-treatment rectal and bladder bleedings were 17,4 and 13,6%, respectively. According to a 1-4 scale adapted from M.D. Anderson Cancer Center criteria: rectal bleedings were grade 1 (9.6%), grade 2 (6.2%) and grade 3 (1.6%). Bladder bleedings were grade 2 (13%) and grade 3 (0.6%). Analysis of rectal bleeding risk factors showed significant correlations with pelvic lymph nodes irradiation for grade 2 and 3, (P = 0.02), and for all grades, a correlation with smaller rectal wall volumes (P = 0.03), and greater percentages of rectal wall irradiated to higher doses: 65, 70, 72 and 75 Gy (P = 0.02, P = 0.01, P = 0.0007 and P 0.003, respectively). Conclusions: these results are comparable to those previously reported with the same follow-up. Impact of dose escalation with short androgen deprivation on local control, survival and complications needs longer follow-up and further analysis. (authors)