A randomized study of two doses of abdominopelvic radiation therapy for patients with optimally debulked Stage I, II, and III ovarian cancer.

PURPOSE

To determine whether an increased dose of abdominal radiation therapy results in improved disease control and survival in patients with early ovarian cancer.

METHODS AND PATIENTS

Between 1981 and 1990, 125 patients with optimally debulked Stage I, II, and III ovarian cancer were entered into a prospective randomized clinical trial of abdominopelvic radiation therapy. Patients were stratified and randomized to either the control arm, treated with an abdominal dose of 22.5 Gy in 22 fractions, or the experimental arm of 27.5 Gy in 27 fractions. A pelvic boost dose of 22.5 Gy was used in both arms. There were 43 patients with Stage I tumors, 71 Stage II tumors, and 11 Stage III tumors. Nineteen patients had grade 1 histology, 77 grade 2, and 29 grade 3. Three patients had small-volume residual disease (<2 cm) in the pelvis alone and the remainder had no gross tumor following surgery. Median follow-up was 6.6 years (range 1.4-9.9).

RESULTS

Overall survival (OS) at 5 years was 83% in the low-dose arm and 72% in the high-dose arm (p = 0.3). Disease-free survival (DFS) at 5 years was 74% and 67% in the low-dose and high-dose arms, respectively (p = 0.5). The difference in OS between the two arms was -11%, with 95% confidence intervals of -26% (favoring low-dose treatment) to 4% (in favor of high dose). The difference in DFS was -7% (95% confidence interval, -23 to 9%). Failure in the pelvis alone predominated (n = 15); six patients had abdominal and pelvic failure and seven patients failed in the abdomen alone. There were no differences in patterns of relapse, hematologic toxicity, or late complications between the two arms. Serious bowel toxicity was seen in three patients: two in the low-dose and one in the high-dose arm. A Cox proportional hazards model was used to assess the effect of treatment when adjusting for other prognostic variables. Ascites (p = 0.03, relative risk 2.05) was the only significant covariate in predicting disease-free survival, but was not prognostic for overall survival.

CONCLUSIONS

There was no difference in survival, tumor control, or toxicity between high-dose and low-dose abdominopelvic radiation therapy. High-dose abdominopelvic radiation therapy is unlikely to be associated with an increase in OS of more than 4% or DFS of more than 9%.