An observational study investigating failure of primary endocrine therapy for operable breast cancer in the elderly

Elderly patients are more likely to have oestrogen receptor positive cancers that can be treated without surgery with primary endocrine therapy (PET). Few studies have sought to identify predictors of failure of PET and so the aim of this study was to evaluate treatment failures in elderly breast cancer patients treated with PET and to determine predictors of failure. A retrospective observational study was performed on consecutive patients with ER-positive early stage breast cancer treated with PET between 2005 and 2015 in the three breast units in the North East of England. The primary outcome measure was treatment failure and secondary outcome measure was disease progression. 488 patients were included with mean follow-up 31 months (SD 23). Overall, 206 patients were still alive with their disease controlled at the end of follow-up, 219 had died with their disease controlled and 63 (12%) experienced treatment failure. Younger age [SHR 0.96 (95% CI 0.94-0.99) p 0.013], larger tumours [SHR 1.03 (1.01-1.06) p 0.015], grade 3 cancers [SHR 3.58 (1.93-6.63) p < 0.001] and axillary lymph node metastases [SHR 1.93 (1.06-3.52) p 0.030] were all independent predictors of treatment failure. Disease progression was reported in 86 (17.6%) of patients. This is the largest retrospective series evaluating PET treatment failure. Clear predictors of failure have been identified, which can be used to facilitate treatment decision making. These results support previous analyses, further validating our results.