Predictors of response to second-line endocrine therapy for breast cancer

This study reports on factors predicting response tosecond-line endocrine therapy in 250 patients with breastcancer for which they were assessable for responseby the International Union Against Cancer (UICC) criteria.Clinical details relating to first-line endocrine therapy wereavailable for all patients. We have not includedin this study patients who received first-line endocrinetherapy but did not or have not yetproceeded to second-line hormone therapy – e.g. diedfrom rapidly progressive disease, started chemotherapy for rapidlyprogressive disease, or remained in long-term remission onfirst-line endocrine therapy.One hundred and fifty nine patients (72%) achievedremission (objective response and static disease OR +SD]) on first-line endocrine therapy with a medianduration of 19 months. For second-line endocrine therapythe remission rate was 53% (132/225) with amedian duration of 15 months. Tumour grade andoestrogen receptor status of the primary tumour wereshown to be independent predictors of response tosecond-line endocrine therapy while response to first-line endocrinetherapy was a predictor of the duration ofresponse to second-line endocrine therapy. In the sub-groupof patients who showed OR or SD toboth first and second-line therapies, there was nocorrelation between the time to progression (TTP) onfirst and second-line therapies.