Metastatic pattern and response to endocrine therapy in human breast cancer

The effect of endocrine therapy in 465 postmenopausal patients with advanced breast cancer who entered four consecutive, randomized trials has been related to the site of the metastases. Patients received either tamoxifen (T) alone or T in combination with medroxyprogesterone acetate, diethylstilbestrol, halotestin, or aminoglutethimide. The overall response rate was 40%. Responses were most frequently seen in patients with metastases in soft tissue, and the duration of response to endocrine therapy in these patients was longer than for those with metastases in bone or viscera (p less than 0.00001). In addition, the response rate was inversely correlated with the number of main metastatic sites in patients with soft tissue metastases, whereas the response rate was not associated with the number of metastatic sites in patients with metastases in bone and viscera. Survival after first recurrence was significantly longer in responding patients with soft tissue lesions compared to those with recurrence in bone or viscera. In contrast, survival after first recurrence was identical in patients with nonresponding disease, irrespective of dominant site of metastases. The outcome of endocrine therapy depends partially upon the dominant site of metastases. This may reflect a difference in biological characteristics of human breast cancer tumor cells that metastasize to different sites.