Acute toxicity of three-dimensional conformal radiotherapy in prostate cancer patients eligible for implant monotherapy

Purpose: To assess the acute toxicity of three-dimensional conformal radiotherapy (3D-CRT) in prostate cancer patients eligible for implant monotherapy, Methods and Materials: Between December 1991 and June 1998, 198 prostate cancer patients were treated with 3D-CRT at the University of California Davis Medical Center. Fifty-two of these patients had a prostate-specific antigen (PSA) level less than or equal to 10.0 ng/ml, Gleason score less than or equal to 6, and a 1997 AJCC clinical stage T1bN0-T2bN0. Eleven (21%) patients received radiotherapy to the prostate and seminal vesicles; the remaining patients were treated to the prostate only. The 3D-CRT treatment planning guidelines in Radiation Therapy Oncology Group (RTOG) 9406 were followed after 1994 (similar treatment planning was used before the protocol became available). Typically, 4 oblique and 2 lateral fields were treated, All patients were seen at least weekly while under treatment, 1 month postirradiation and then every 3 months, Total radiation doses ranged from 66.0-79.2 Gy, with a median dose of 73.8 Gy in 41 fractions over 8 weeks. Acute toxicity is described according to the RTOG acute toxicity scoring system. Results: Overall, 3D-CRT was well-tolerated: 29% of patients experienced RTOG Grade 1 and 27% experienced Grade 2 acute lower gastrointestinal (GI) toxicity, Forty percent and 33% of patients experienced Grade 1 and 2 acute genitourinary (GU) toxicity, respectively. As expected, more acute morbidity, especially GI, was observed with a Larger clinical target volume (prostate and seminal vesicles versus prostate only; p = 0.05). Neoadjuvant hormonal therapy did not increase the incidence or severity of radiation-induced side effects. No acute toxicity greater than or equal to Grade 3, e.g., hourly nocturia, gross hematuria, diarrhea requiring parenteral support, narcotics for pain control, or catheterization for acute urinary retention, was observed. Conclusion: Although relatively high doses of radiation are delivered to prostate cancers with 3D-CRT compared with conventional radiotherapy, 3D-CRT is surprisingly well-tolerated. No patients in the cohort eligible for implant monotherapy experienced acute toxicity greater than or equal to Grade 3. (C) 2000 Elsevier Science Inc.