Radiation dose response in patients with favorable localized prostate cancer (Stage T1-T2, biopsy Gleason <= 6, and pretreatment prostate-specific antigen <= 10)

Purpose: To study the radiation dose response as determined by biochemical relapse-free survival in patients with favorable localized prostate cancers , i.e., Stage T1-T2, biopsy Gleason score (bGS) less than or equal to 6, an d pretreatment prostate-specific antigen (iPSA) less than or equal to 10 ng /mL, Methods and Materials: A total of 292 patients with favorable localized pro state cancer were treated with radiotherapy alone between 1986 and 1999. Th e median age was 69 years. Sixteen percent of cases (n = 46) were African-A merican. The distribution by clinical T stage was as follows: T1/T2A, 243 ( 83%); and T2B/T2C, 49 (17%). The distribution by iPSA was as follows: less than or equal to 4 ng/mL, 49 (17%); and > 4 ng/mL, 243 (83%), The mean IPSA level was 6.2 (median, 6.4), The distribution by bGS was as follows: less than or equal to 5 in 89 cases (30%) and 6 in 203 cases (70%), The median r adiation dose was 70.0 Gy (range, 63.0-78.0 Gy), Doses of less than or equa l to 70.0 Gy were delivered in 175 cases, 70.2-72.0 Gy in 24 cases, 74 Gy i n 30 cases, and 78 Gy in 63 cases. For patients receiving < 72 Gy, the medi an dose was 68 Gy, vs. 78 Gy for patients receiving greater than or equal t o 72 Gy. A conformal technique was used in 129 (44%) of cases. The median f ollow-up was 43 months (range, 3-153). Results: For the entire cohort, the projected 5- and 8-year biochemical rel apse-free survival (bRFS) rates were both 81%. For patients receiving great er than or equal to 72 Gy, the 5- and g-year bRFS rates were both 95% vs. o nly 77% for patients receiving ( 72 Gy,p = 0,010. For patients receiving 74 Gy, the 4-year bRFS rate was 94% vs. 96% for patients receiving 78 Gy, p = 0.90, A multivariate analysis for factors affecting bRFS rates using Cox p roportional hazards was performed for all cases using the following variabl es: age (continuous variable), race (black vs, white), iPSA (continuous var iable), bGS (less than or equal to 5 vs. 6), Stage (T1-2A vs. T2B-C), radia tion dose (continuous variable), and radiation technique (conformal vs. sta ndard). From the multivariate analysis, only iPSA (p = 0,017, chi (2) = 5,7 ), and radiation dose (p = 0,021, chi (2) = 5,3) were independent predictor s of outcome. Age (p = 0,94), race (p = 0,89), stage (p = 0.45), biopsy GS (p = 0,40), and radiation technique (p = 0.45) were not. Conclusion: There is a clear radiation dose response in patients with favor able localized prostate cancers (i.e., Stage T1-T2, biopsy Gleason score le ss than or equal to 6, and iPSA less than or equal to 10 ng/mL). At least 7 4 Gy should be delivered to the prostate and periprostatic tissues. With ou r cohort of patients, longer follow-up will be needed to assess the importa nce of doses exceeding 74 Gy, (C) 2001 Elsevier Science Inc.