Adherence to Adjuvant Endocrine Therapy in Christchurch Women with Early Breast Cancer.

AIMS: To assess adherence to adjuvant endocrine therapy by a real-world cohort of women in Christchurch and to determine any associated factors.

MATERIALS AND METHODS: Records were retrieved of all women newly diagnosed with early breast cancer and registered on the Christchurch Breast Cancer Patient Register over 4 years from June 2009. Demographic and pathological factors, dates of starting and stopping endocrine therapies and reported side-effects were collected. The proportion remaining on endocrine therapy was analysed by Kaplan-Meier curve; Cox regression analysis was used to identify independent factors influencing adherence.

RESULTS: Of 1213 women, 1018 (83.9%) had oestrogen receptor-positive tumours, of whom 674 (66.2%) started adjuvant endocrine therapy, including 62 (9.2%) neoadjuvantly. Uptake was 52.4% of those with T1 tumours, 89% with T2 tumours, 93% with T3/T4 tumours, 92.7% with node-positive tumours and 49.7% with node-negative tumours. The initial endocrine therapy was an aromatase inhibitor in 254 (38%) and tamoxifen for 412 (61%). At 1 year, 90% remained adherent, at 2 years 84%, at 3 years 81%, at 4 years 76%, at 4.5 years 71% and at 5 years 50%, with a median duration of 60 months (56-64 months, 95% confidence interval) and a median follow-up of 33 months. Overall, 135 (20%) women stopped treatment for adverse events or poor tolerability. A longer persistence with endocrine therapy was associated with node-positive tumours (hazard ratio 1.38, P = 0.003), but not first hormone used; aromatase inhibitor compared with tamoxifen, P = 0.76.

CONCLUSION: Adjuvant endocrine therapy use fell to 50% by 5 years, limiting possible survival benefits, providing support for efforts to increase compliance.