Endocrine therapies for patients with recurrent breast cancer: predictive factors for responses to first- and second-line endocrine therapies

Breast cancer patients have been treated with four different hormonal agents, antiestrogen, progestin, luteinizing hormone-releasing hormone agonist and aromatase inhibitor, during the past 7 years in Japan. To investigate the efficacy of these agents for the treatment of recurrent breast cancer patients, we conducted a retrospective multi-institute survey in Japan. The clinico-pathological data of 131 patients, who received endocrine therapy as first-line treatment between 1993 and 1998, were collected from seven institutes. The median age of the patients was 55 (range 27-92) years, 75% of their primary tumors were estrogen receptor (ER)-positive or unknown, and 95% of the dominant metastatic sites were bone, soft tissue or lungs. The objective response rate to first-line endocrine therapy was 42.7%, and that to second-line therapy 42.5% (17 of 40 patients). Multiple regression analyses of predictive factors for a response to first- and second-line endocrine therapies indicated two independent factors, ER status of the primary tumors and dominant site of metastasis, for the former, and one independent factor, a response to first-line endocrine therapy, for the latter. Analysis of relationships between sequences of use of hormonal agents and objective response rates revealed that the choice of first-line hormonal agent did not influence the overall efficacy of first- and second-line endocrine therapies. Overall survival after first recurrence in patients with tumors exhibiting an objective response or stable disease to first-line endocrine therapy was significantly better than that in patients with tumors exhibiting progressive disease (p < 0.01). These findings suggest that an adequate selection of recurrent breast cancer patients referring the ER status, dominant site of metastasis and a prior response to endocrine therapy may contribute to better clinical outcomes of the patients.