Abstract P1-07-36: Outcomes and failure of primary endocrine therapy for operable breast cancer in the elderly: A regional North-east of England study

Introduction Primary Endocrine therapy (PET) to treat oestrogen receptor (ER) positive operable breast cancer in the elderly is used widely in the UK. A previous Cochrane analysis revealed its inferiority in long-term local control in comparison to surgery. As such, current guidance from the Society of International Geriatric Oncologists (SIOG) suggest that PET should be reserved for patients with a reduced life-expectancy (2-3 years) or for those considered unfit for surgery. Inaccurate assessment of life expectancy could lead to treatment failure which is potentially catastrophic for the patient. The aim of this study was to evaluate treatment failures in elderly breast cancer patients treated with PET and to determine predictors of failure. Methods 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 the secondary outcome measure was disease progression. Results 488 patients were included with mean follow up 31 months (SD 23). 465 (95.2%) patients were started on Letrozole as their initial therapy. 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. Kaplan-Meier survival analysis predicted at 3 years 40% of patients to have died with controlled disease and 10% to have failed, leaving 50% living beyond this point with controlled disease. Regression analysis identified younger age [SHR 0.96 (95% CI 0.94 to 0.99) p 0.013], larger tumours [SHR 1.03 (1.01 to 1.06) p 0.015], grade 3 cancers [SHR 3.58 (1.93 to 6.63) p Conclusions This is the largest retrospective series conducted evaluating PET treatment failure. Our comparably low rate of failure in comparison to that in the literature (12-85%) reflects good clinical acumen. Clear predictors of failure have been identified, which support previous analyses, further validating our results. Patients are able to live longer term (beyond 3 years) and maintain local disease control, which may represent a viable long-term treatment in the absence of risk factors for failure. Further work on our series is underway examining the effect of decision-making on PET outcomes. Citation Format: Thomas R, Rowell R, Crichton S, Cain H. Outcomes and failure of primary endocrine therapy for operable breast cancer in the elderly: A regional North-east of England study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-07-36.