• P A Kupelian, J C Buchsbaum, C A Reddy, and E A Klein.
• Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH 44195, USA. kupelian@radonc.ccf.org
• Int. J. Radiat. Oncol. Biol. Phys. 2001 Jul 1; 50 (3): 621-5.

PurposeTo 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) < or = 6, and pretreatment prostate-specific antigen (iPSA) < or = 10 ng/mL.Methods And MaterialsA total of 292 patients with favorable localized prostate cancer were treated with radiotherapy alone between 1986 and 1999. The median age was 69 years. Sixteen percent of cases (n = 46) were African-American. 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: < or = 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: or = 5 in 89 cases (30%) and 6 in 203 cases (70%). The median radiation dose was 70.0 Gy (range, 63.0-78.0 Gy). Doses of < or = 70.0 Gy were delivered in 175 cases, 70.2-72.0 Gy in 24 cases, 74 Gy in 30 cases, and 78 Gy in 63 cases. For patients receiving < 72 Gy, the median dose was 68 Gy, vs. 78 Gy for patients receiving > or = 72 Gy. A conformal technique was used in 129 (44%) of cases. The median follow-up was 43 months (range, 3-153).ResultsFor the entire cohort, the projected 5- and 8-year biochemical relapse-free survival (bRFS) rates were both 81%. For patients receiving > or = 72 Gy, the 5- and 8-year bRFS rates were both 95% vs. only 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 proportional hazards was performed for all cases using the following variables: age (continuous variable), race (black vs. white), iPSA (continuous variable), bGS (< or = 5 vs. 6), Stage (T1-2A vs. T2B-C), radiation dose (continuous variable), and radiation technique (conformal vs. standard). 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 predictors 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.ConclusionThere is a clear radiation dose response in patients with favorable localized prostate cancers (i.e., Stage T1-T2, biopsy Gleason score < or = 6, and iPSA < or = 10 ng/mL). At least 74 Gy should be delivered to the prostate and periprostatic tissues. With our cohort of patients, longer follow-up will be needed to assess the importance of doses exceeding 74 Gy.

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