Efficacy of radiotherapy for ovarian ablation: Results of a breast intergroup study

BACKGROUND. In 1994, the Eastern Cooperative Oncology Group (ECOG) initiated for the Breast Intergroup a randomized clinical trial (E3193) in premenopausal patients with early-stage breast carcinoma (lymph node-negative and receptor-positive, with tumors measuring ≤ 3 cm) comparing tamoxifen as adjuvant systemic therapy with tamoxifen and ovarian ablation by one of three different methods. Ovarian ablation could be accomplished either via radiotherapy (RT) (20 Gray [Gy]/10 fractions to a modified pelvic volume), surgical oophorectomy, or goserelin/leuprolide injections as per patient/physician choice. In the current study, we report the efficacy of pelvic RT with this dose-fractionation scheme in the induction of ovarian ablation. METHODS. Twenty-two of 174 patients (13%) who were randomized to treatment with tamoxifen and ovarian ablation received RT for ovarian ablation. RT quality assurance was performed. Of the 22 patients, 19 were treated per protocol, 1 patient had a minor violation (20 elapsed days for 10 RT fractions), and 2 patients had major violations (1 patient who was treated with RT as per protocol but who was treated at a non-Intergroup center, and 1 patient who was treated at a dose of 15 Gy/5 fractions). RESULTS. No acute Grade 3 or 4 (according to the Common Toxicity Criteria of the National Cancer Institute) toxicities were reported during RT. Of the 22 patients receiving RT, evaluable follow-up data were available for 20 patients. Based on postmenopausal levels of estradiol or follicle-stimulating hormone at varying intervals after the completion of RT, 15 of 20 patients (75%) achieved successful ovarian ablation with RT. At a median follow-up of 54 months (range, 21-66 months), no Grade 3 or 4 complications from RT were observed. CONCLUSIONS. Ovarian ablation by RT as performed in the current trial (given at a dose of 20 Gy in 10 fractions to a modified pelvic treatment volume) was found to be effective for ovarian ablation in the majority of patients, but may take some months to be complete. Consequently, patients should be evaluated to ascertain that ablation has been accomplished.