Long-Term Outcome of Sustained Endocrine Monotherapy for Elderly Breast Cancer Patients

Background: Among elderly breast cancer patients, endocrine therapy may be chosen as definitive treatment by patients or physicians. This study investigated the efficacy of endocrine monotherapy (ET) in terms of avoidance of invasive local treatment. Methods: Elderly patients (≥70 years) with a diagnosis of estrogen receptor-positive breast cancer who underwent ET between 2008 and 2015 were identified through the Netherlands Cancer Registry. The primary outcome was the cumulative risk of undergoing invasive local treatment (radiotherapy or surgery) for the primary tumor. The secondary outcomes were development of uncontrolled local disease and overall survival (OS). Results: Of the 105 patients (median age, 86 years) enrolled in this study, 91 (78 %) received ET as definitive treatment, whereas 14 received ET as a “bridge to surgery.” For the 91 patients who used ET as intended definitive treatment, the 5-year cumulative risk of undergoing invasive local treatment and experiencing uncontrolled disease were respectively 28 % and 16 %. The 5-year cumulative OS was 42 %. Whereas 11 patients had metastatic or locally progressive breast cancer at the time of death, cardiovascular disease, infectious diseases, and old age or dementia were reported as contributing to the death of 39 patients. Conclusions: For a select group of elderly breast cancer patients who received sustained ET, the risk of undergoing invasive local treatment was surpassed by a twofold higher risk of dying. As an alternative to invasive local treatment, ET can be discussed as a safe and effective option for patients unwilling or unfit to undergo surgery.