We sought to determine the proportion of women with early breast cancer (EBC) who stop/switch endocrine therapy (ET) and the reasons for these changes.
We identified women aged ≥50 years, diagnosed with stage 1-3, ER/PR positive EBC and starting ET between January 2008 and June 2010. We recorded: demographics; ET type, duration, and toxicity; recurrences and survival from EBC diagnosis.
Of 217 women with ER/PR positive EBC, 172 (79%) started ET. Median age at diagnosis was 62 years (range 50-89), 148 (87%) were post-menopausal and 69 (40%) received adjuvant chemotherapy. Reasons for not starting ET were: not recommended by doctor (46%), fear of toxicity (30%), and patient declined (12%). The most commonly prescribed first-line ET was anastrozole (59%), followed by Tamoxifen (26%). The median duration on ET was 60 months (range 1-92), with 66 women (38%) completing 5 years, and another 47 (27%) continuing >5 years. The number of ET agents received in the first 5 years was: 1 (58%); 2 (30%); and ≥3 (12%). Of women starting aromatase inhibitors (AI), 41% changed ET due to toxicity; 46% switched to Tamoxifen, 23% switched to another AI and 14% stopped ET. 59% of women starting AI completed ≥5 years of ET. Of women starting tamoxifen, 55% changed ET and 45% completed ≥5 years of ET. The most common reasons for stopping first-line ET were arthralgia (28%) and hot flushes (9%). With 5.4 years median follow-up, 18 women (7%) had a recurrence, (8 on ET, 5 after stopping ET, and 5 who never started ET), and 21 women (10%) have died.
One third of women recommended adjuvant ET never start or stop prematurely. Measures to improve uptake and adherence in these women are important to reduce BC recurrences.