Dose–volume relationship for acute side effects during high dose conformal radiotherapy for prostate cancer

Purpose: To determine acute and late complications for bladder and rectum and to determine dose–volume correlations. Methods and materials: Sixty-four patients received definitive treatment for prostate cancer between January 1995 and December 1998 using conformal three-dimensional radiotherapy. Doses ranged from 72 to 80 Gy. The acute and late side effects were gathered retrospectively, and graded according to Radiotherapy and Oncology Group criteria (RTOG). The patients were divided into two groups: ≤72 Gy (Group A) and ≥76 Gy (Group B) and had a mean follow-up of 32 and 22 months, respectively. Results: No grades 3–4 acute, urinary or rectal toxicity was reported. Acute grade 2 rectal complications were seen in 10 and 18% of the patients in Groups A and B, respectively. They were observed at a mean dose of 38 Gy. Acute grade 2 urinary symptoms were 33 and 47% for Groups A and B, respectively. They were seen at a mean dose of 43 Gy. Acute rectal symptoms were dose–volume related. Patients without diarrhea had a mean rectal volume receiving a dose of 70 Gy or more of 8.5 cm³. However, patients with RTOG 2 diarrhea had a volume of 16.5 cm³ (P=0.042). No dose–volume relationship for acute bladder symptoms or late complications were seen. Grades 1–2 late rectal and bladder complications were seen in 11 and 8% of the patients, respectively. None required hospital admission or transfusion. Conclusion: Radiotherapy to the prostate can be given at 80 Gy. No grades 3–4 acute, urinary or rectal toxicity was reported. Acute rectal symptoms are dose–volume related.