Dose escalation for localized prostate cancer: substantial benefit observed with 3D conformal therapy.

Abstract

To determine the effect of radiation dose escalation on biochemical and/or disease failure in patients with localized prostate cancer treated with three-dimensional conformal radiotherapy (3D-CRT). Between May 1987 and December 2000, 1473 patients were assessed after treatment with 3D-CRT. The mean patient age was 70.4 +/- 6.8 years, 1316 patients had T1-T2 disease, and 1150 had Gleason score <or=7. The median pretreatment prostate-specific antigen (PSA) level was 8.9 ng/mL. The mean dose was 71.7 +/- 4.3 Gy (range 60.0-80.4). Failure was defined as the first event of any of the following: biochemical failure, local recurrence or metastasis, postirradiation hormonal therapy, or death from disease. At a median follow-up of 35.2 months, 395 failures (26.8%) had occurred. Adjusting for dose as a continuous variable, the hazard ratio for failure was 2.03 (p < 0.0001) for 569 intermediate-risk patients (stage T1-T2 and Gleason score 7 or PSA 10-20 ng/mL) and 5.16 (p < 0.0001) for 456 high-risk patients (stage T3-T4 or PSA >20 ng/mL or Gleason score >or=8) compared with 448 low-risk patients (stage T1-T2 and Gleason score <or=6 and PSA <10 ng/mL). For intermediate-risk patients, each 1-Gy increment in total radiation dose was associated with a highly significant 8% reduction in the probability of failure (hazard ratio = 0.92, p = 0.005). Dose escalation using 3D-CRT significantly reduces the risk of biochemical/disease failure among intermediate-risk prostate cancer patients.