Management and outcomes for older women with early breast cancer treated with primary endocrine therapy (PET).

Background: This study reports the detailed management and outcomes of women treated with Primary Endocrine Therapy (PET) in a large prospective UK cohort of older women (≥70) with breast cancer.

Methods: This was an unplanned secondary analysis of a prospective, multicentre, observational study (The Age Gap study). Data were collected at baseline and regular intervals on patient, tumour and treatment characteristics with tumour RECIST response category recorded. Direct study follow-up was 24 months with longer-term survival data obtained from the UK cancer registry.

Results: The Age Gap study recruited 3316 women across 56 breast units. Primary endocrine therapy (PET) was initiated for 505/3316 (15 %) women; median age was 84 (IQR 79-88) with median follow-up 41.9 months (IQR 27-60). Death occurred in 205/505(40.6 %) patients, 160/205; 78 % non- Breast Cancer related, 45/205; 21.9 % Breast Cancer related. Multivariate analysis identified older age (HR-1.055(95 % Confidence Interval: 1.029-1.084); P < 0.001) and higher Charlson Index (HR-1.166 (1.086-1.252); P < 0.001) as risk factors for all-cause mortality, but conversion to surgery (HR-0.372(0.152-0.914); P = 0.031) was protective. Grade 3 cancer (G1 vs G3 HR-0.28 (0.094-0.829); P = 0.022 & G2 vs G3 HR-0.469 (0.226-0.973); P = 0.042), axillary positivity (axilla positivity HR-2.548 (1.321-4.816); P = 0.005) and change of endocrine therapy (HR-3.010 (1.532-5.913); P = 0.001) were associated with worse breast cancer specific survival (BCSS). RECIST category was not significantly associated with either overall survival or BCSS (P > 0.05).

Conclusion: Early disease response and change of endocrine therapy are not significantly associated with overall survival, conversion to surgery is linked to improved outcome. Prognosis is largely determined by age and comorbidity in older women treated with PET.