Adverse effects of preoperative radiation therapy for rectal cancer: long-term follow-up of the Swedish Rectal Cancer Trial.

To analyze the occurrence of subacute and late adverse effects in patients treated with preoperative irradiation for rectal cancer. The study population included 1,147 patients randomly assigned to preoperative radiation therapy or surgery alone in the Swedish Rectal Cancer Trial conducted 1987 through 1990. Patient data were matched against the Swedish Hospital Discharge Register to identify patients admitted to hospital after the primary treatment of the rectal cancer. Patients with known residual disease were excluded, and patients with a recurrence were censored 3 months before the date of recurrence. Relative risks (RR) with 95% CIs were calculated. Irradiated patients were at increased risk of admissions during the first 6 months from the primary treatment (RR = 1.64; 95% CI, 1.21 to 2.22); these were mainly for gastrointestinal diagnoses. Overall, the two groups showed no difference in the risk of admissions more than 6 months from the primary treatment (RR = 0.95; 95% CI, 0.80 to 1.12). Regarding specific diagnoses, however, RRs were increased for admissions later than 6 months from the primary treatment in irradiated patients for unspecified infections, bowel obstruction, abdominal pain, and nausea. Gastrointestinal disorders, resulting in hospital admissions, seem to be the most common adverse effect of short-course preoperative radiation therapy in patients with rectal cancer. Bowel obstruction was the diagnosis of potentially greatest importance, which was more frequent in irradiated than in nonirradiated patients.