An individual patient-based meta-analysis of tamoxifen versus ovarian ablation as first line endocrine therapy for premenopausal women with metastatic breast cancer

We performed a meta-analysis of randomized trials comparing tamoxifen to ovarian ablation carried out either by surgery or irradiation as first-line hormonal therapy for pre menopausal women with metastatic breast cancer. Patients in all trials included were required to have measurable disease and to be currently menstruating or within 1 year of cessation of menses, and to have estrogen receptor (ER) positive or unknown disease (ER negative women were admitted to one of the studies). Individual patient data were obtained from the four studies identified and the results updated to June 1992. A total of 220 eligible patients were enrolled in the four trials. There was no difference in overall response rate between tamoxifen and oophorectomy across the four trials (p = 0.94, Mantel-Haenszel test). The odds reduction for progression was 14% +/- 12% and for mortality 6% +/- 13 % in favour of tamoxifen, results which were not statistically significant (p = 0.32 and 0.72, respectively). Although the design of all four studies included a cross-over to the other therapy, only 54/111 patients receiving ovarian ablation and 34/109 patients receiving tamoxifen as primary therapy actually crossed over to the other arm at the time of disease progression. Response to initial treatment with tamoxifen was predictive of subsequent response to ovarian ablation (p < 0.05), and response to initial therapy with ovarian ablation was predictive of subsequent response to tamoxifen (p < 0.05). Support curves based on log-likelihood ratios revealed that this meta-analysis provides moderate evidence rejecting a 14% advantage for ovarian ablation compared to tamoxifen in terms of odds of disease progression. A 25% advantage for ovarian ablation with respect to odds of death is also rejected with moderate evidence. We conclude that the efficacy of tamoxifen appears to be similar to that of ovarian ablation by surgery or irradiation as first-line therapy for premenopausal, ER positive metastatic breast cancer, and is unlikely to be substantially inferior.