Change in practice patterns over time for endocrine therapy (ET) and radiation therapy (RT) in women with breast cancer age 65 and older.

Abstract

e12574 Background: In 2016, the American College of Surgeons (ACS) recommended omitting RT for women over age 70 with stage 1, HR+ breast cancer after lumpectomy. However, the optimal treatment approach for these patients remains uncertain since there are challenges with both ET and RT. Actual and perceived barriers exist for receipt of RT. Conversely, many women develop side effects from ET, which can lead to early discontinuation. We examined how localized and systemic treatment patterns for women age 65+ have changed over time, and examine differences in recurrence rates. Methods: Women with HR+, HER2 negative, clinically node negative breast cancer aged 65+ diagnosed 2012-2021 who underwent lumpectomy +/- SLNB at a single institution were included. We omitted patients diagnosed in 2020 as treatment may have been altered due to the global pandemic. The treatment groups of ET only, RT only, both ET and RT, and neither ET nor RT were compared by patient age, year of diagnosis, and recurrence rates. Fisher's Exact Test was used to compare treatment groups, and competing risk analysis was used to examine recurrence rates. Results: The 391 women had tumors with ductal (79%), lobular (17%), and other (4%) histology; tumor size was <= 10 mm (41%), <10-20 mm (42%), <2-5 cm (16%), and > 5 cm (0.2%). 6% of patients underwent chemotherapy; 75% had axillary surgery. A total of 108 (28%) had ET only, 34 (9%) RT only, 208 (53%) both ET and RT, and 40 (10%) neither ET nor RT. Treatment regimens by year of diagnosis and age are given in Table 1. Compared to patients treated with both ET and RT, risk for recurrence for those treated with neither ET nor RT was hazard ratio (HR) 8.52 (95% CI 3.2-22.9, P < .001), for ET alone was HR 3 (95% CI 1.3-7.2, p=.013), and for RT alone was HR 1.31 (95% CI 0.3-6.3, p=.74). Recurrences occurred in patients who received neither ET nor RT [8 (20%) local and 2 (5%) contralateral breast], ET alone [9 (8%) local, 1 (1%) contralateral breast and 2 (2%) distant], RT alone [2 (6%) local], and both ET and RT [4 (2%) local, 3 (1%) contralateral breast and 3 (1%) distant]. Conclusions: Fewer older women underwent both ET and RT as well as RT alone after the publication of the ACS guidelines. However, recurrence risks were higher for those receiving only ET, possibly because of poor adherence to ET, and those who underwent neither ET nor RT. Given the new data regarding effectiveness of shorter RT treatment courses and concerns about recurrence without adjuvant therapy, these results support the conduct of larger studies evaluating RT alone following lumpectomy in this patient population. Treatment regimens by year of diagnosis and patient age. Factor ET and RT ET only RT only No ET or RT P value 2012-2013 58 (67%) 11 (13%) 12 (14%) 6 (6.9%) .003 2015-2016 58 (47%) 42 (34%) 10 (8.1%) 13 (11%) 2019-2021 92 (51%) 55 (31%) 12 (6.7%) 21 (12) Age 65-<70 107 (75%) 18 (13%) 14 (9.8%) 4 (2.8%) <.001 Age 70-<80 93 (48%) 63 (32%) 16 (8.2%) 23 (12%) Age 80+ 4 (8.7%) 27 (59%) 2 (4.3%) 13 (28%)