Clinical Research Fellow Memorial Sloan Kettering Cancer Center New York, New York, United States
Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
Participants should be aware of the following financial/non-financial relationships:
Regina Matar, MD: I do not have any relevant financial / non-financial relationships with any proprietary interests.
Introduction: NCCN guidelines recommend radiotherapy (RT) omission in women ≥70 years with ER+, cN0, T1 tumors undergoing lumpectomy due to a lack of survival benefit and little decrease in LRR rates if they receive endocrine therapy (ET). However, little is known about ET adherence in older women managed without RT and the impact of poor adherence on LRR.
Methods: Women age ≥70 years with pT1-2, ER+ breast cancer undergoing lumpectomy without RT from 2004-2019 were identified from a prospectively maintained database. ET adherence, calculated as treatment duration over follow-up time up to 5 years, was determined by chart review. We compared clinicopathologic characteristics and rates of LRR between women with high adherence (≥80%), low adherence ( < 80%), and no ET.
Results: Of 968 women (27 bilateral cancers), adherence was high in 676 (70%) and low in 162 (17%); 130 (13%) took no ET. Younger age and aromatase inhibitor use (vs tamoxifen or both) were associated with high adherence, while race and period of surgery (2004-2010 vs 2011-2019) were not. At 53 months (IQR 30-76) of median follow-up, there were 80 LRR events. Crude rates of LRR were significantly lower in women with high adherence (4%; 30/692) than in those with low adherence (16%; 27/168) and no ET (17%; 23/135) (p < 0.001; Table). Age, histology, nuclear grade, multifocality, LVI, pN stage, and DCIS within 2mm of surgical margins were not associated with LRR. On multivariable analysis, tumor size (HR 1.67, 95% CI 1.03-2.68, p=0.04) and high adherence (HR 0.13, 95% CI 0.07-0.26, p < 0.001) were significantly associated with LRR. The 5-year rate of LRR was 3.1% (95% CI 1.6-4.6%) for high adherence, 14.7% (95% CI 8.9-20.6%) for low adherence, and 17.9% (95% CI 10.1-25.6%) for the no ET group (p < 0.01).
Conclusions: Although adherence to ET was high overall, in the 30% of women with low adherence or who did not take ET, LRR rates were significantly increased. Counseling regarding the distinct toxicities of RT and ET can help patients choose therapy they will likely comply with, and studies to identify those at high risk of non-adherence to ET are needed, as they may benefit from RT.
Learning Objectives:
Upon completion, participant will be able to characterize outcomes among older women managed with lumpectomy without adjuvant radiotherapy, and with poor adherence to anti-estrogen therapy.
Upon completion, participant will be able to know rates of adherence to endocrine therapy among women > 70 treated with lumpectomy alone.
Upon completion, participant will know factors predictive of adherence to endocrine therapy.
