Response after withdrawal of tamoxifen and progestogens in advanced breast cancer.

Tumor response after withdrawal of endocrine therapy for advanced breast cancer with estrogens and androgens is well described. There have been few reports of withdrawal responses (WRs) after cessation of treatment with the newer antiestrogens and progestogens. We assessed WR in women after cessation of adjuvant therapy at first relapse, and after progression on first, second or third line endocrine therapy for advanced disease. One of seven patients (14%) responded after cessation of tamoxifen adjuvant therapy at relapse. Sixty-five of 72 patients were evaluable for WR after cessation of tamoxifen as first line therapy for advanced disease. There were five partial responses (8%) and 14 (22%) 'no change' with a median duration of WR of 10 months (range 3-40 months). WR were seen mainly in soft tissue disease but there were two responses in lung and two in bone. Four of 21 (19%) patients had a WR after cessation of norethisterone acetate (3) and tamoxifen (1), all used as second line therapy. WR are therefore demonstrable after cessation of tamoxifen and norethisterone acetate with durations of response similar to those found with additive therapy. Assessment of WR may represent a way of prolonging the overall response duration in patients with relatively indolent metastatic breast cancer, particularly in soft tissues.