Toxicity associated with postoperative radiation therapy for prostate cancer.

Objective: To quantify gastrointestinal (GI) and genitourinary (GU) toxicity associated with postprostatectomy radiation and to determine the relationships between dosimetry parameters and medical comorbidities and toxicity.
Methods: We reviewed the records of 233 prostate cancer patients irradiated after prostatectomy between 1987 and 2002. Ninety-nine patients were treated with a volumetric 3-dimensional conformal approach and 134 patients were treated conventionally. Acute and late GI and GU toxicity was recorded and the relationships between dosimetry parameters and comorbidities and toxicity were examined.
Results: Acute grade 2 to 3 GI toxicity was more common in the conventionally versus conformally treated patients (83% vs. 61%, P=0.01). The rates of acute grade 2 to 3 GU toxicity were not significantly different between the techniques. There were no acute grade 4 events. Most patients had no late GI toxicity (73% conformal and 75% conventional) and no late GU toxicity (64% conformal and 59% conventional). In an actuarial analysis, the 5-year rates of grade 2 to 4 GI and GU complications were not different between the treatment techniques. Two patients treated conventionally had late grade 4 complications. Hemorrhoids predicted for late GI toxicity, and renal stones and preirradiation urinary incontinence predicted for late GU complications. Delivery of 50 Gy to more than 38% of the rectal volume, 40 Gy to more than 58%, or 30 Gy to more than 72% was associated with an increased risk of late GI complications. Eighty-seven percent of the late GI complications occurred in patients with at least grade 2 acute GI toxicity.
Conclusions: For prostate cancer patients treated with postoperative radiation, limited toxicity is seen with conventional or conformal techniques. The similar rates of toxicity between techniques may have been because of higher conformal median doses -70 Gy versus 62 Gy. Dose-volume parameters correlate with the risk of GI complications.