Gaither, Rachel

Abstract Background: Young age at diagnosis is an independent risk factor for recurrence and death from breast cancer (BC), with the greatest impact of young age demonstrated in hormone receptor positive (HR+) disease. Younger women are less likely to be adherent to endocrine therapy (ET), which may contribute to disparate outcomes. Methods: As part of a prospective cohort that enrolled women with BC diagnosed at age ≤40 between 2006-2016, we identified women with HR+, Stage I-III BC. Serial surveys with items assessing socio-demographic and treatment information including medication use are administered 1-2 times per year. Medical record review was used to ascertain stage and HR status and to confirm recurrent disease (locoregional, distant, or new primary breast cancer). Women who initiated ET but discontinued it <5-years post-diagnosis without resumption were classified as non-persistent. Univariable and multivariable regression models were fit to identify predictors of non-persistence and recurrence.Results: Among 607 women who initiated ET (median age at diagnosis: 36, range:17-40; 38%, 45%, 17% were Stage 1, 2, and 3, respectively).16% (99/607) were non-persistent, of whom 30% (30/99) discontinued ET ≤2 years post-diagnosis and over half had discontinued (54%, 54/99) by 3 years. In multivariable regression, those who were younger at diagnosis (age ≤30 vs. 36-40: OR: 3.39, 95% CI: 1.84-6.24; age 31-36 vs. 36-40: OR: 2.81 95% CI: 1.70-4.64) were more likely to discontinue ET while those with a higher stage at diagnosis were less likely to discontinue ET (Stage 2 vs. 1: OR: 0.46, 95% CI: 0.29-0.74; Stage 3 vs 1: OR: 0.32, 95% CI: 0.15-0.68). At a median follow-up time from diagnosis of 7.8 years (range 1-13 years), 15% of women (88/607) recurred or developed a new primary BC at a median time from diagnosis of 3.5 years (range 1-12 years). Of these, 66% (58/88) were distant recurrences, 32% (28/88) loco-regional, and 2% (2/88) new primary BCs. Rates of recurrence were higher among women who were persistent (81/508, 16%) vs. non-persistent (7/99, 7%, p=0.02). In multivariable regression, those who were non-persistent were less likely to recur (OR: 0.43, 95% CI: 0.19-0.98) while those with a higher stage were more likely to recur (Stage 3 vs. 1: OR: 2.36, 95% CI: 1.03-5.41). Sociodemographic, patient, and other treatment factors did not predict recurrence. Conclusions: Approximately 16% of young women with HR+ BC stop ET earlier than indicated, however non-persistence was not a risk factor for BC recurrence a median of 8 years following diagnosis in our cohort. Importantly, women with higher risk disease who are likely to benefit most from adherence to ET were less likely to discontinue treatment. Extended follow-up will further inform the impact of non-persistence on the incidence of late recurrences for which women with HR+ BC are at increased risk. Citation Format: Shoshana M Rosenberg, Yue Zheng, Philip Poorvu, Kathryn Ruddy, Rachel Gaither, Rulla Tamimi, Lidia Schapira, Jeffrey Peppercorn, Steven Come, Virginia Borges, Ann Partridge. Endocrine therapy non-persistence and recurrence in young women with early stage breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD2-08.

Objective: We aimed to investigate eligibility for breast conserving surgery (BCS) pre- and post-neoadjuvant systemic therapy (NST), and trends in the surgical treatment of young breast cancer patients. Background: Young women with breast cancer are more likely to present with larger tumors and aggressive phenotypes, and may benefit from NST. Little is known about how response to NST influences surgical decisions in young women. Methods: The Young Women's Breast Cancer Study, a multicenter prospective cohort of women diagnosed with breast cancer at age ≤40, enrolled 1302 patients from 2006 to 2016. Disease characteristics, surgical recommendations, and reasons for choosing mastectomy among BCS-eligible patients were obtained through the medical record. Trends in use of NST, rate of clinical and pathologic complete response, and surgery were also assessed. Results: Of 1117 women with unilateral stage I-III breast cancer, 315 (28%) received NST. Pre-NST, 26% were BCS eligible, 17% were borderline eligible, and 55% were ineligible. After NST, BCS eligibility increased from 26% to 42% (P < 0.0001). Among BCS-eligible patients after NST (n = 133), 41% chose mastectomy with reasons being patient preference (53%), BRCA or TP53 mutation (35%), and family history (5%). From 2006 to 2016, the rates of NST (P = 0.0012), clinical complete response (P < 0.0001), and bilateral mastectomy (P < 0.0001) increased, but the rate of BCS did not increase (P = 0.34). Conclusion: While the proportion of young women eligible for BCS increased after NST, many patients chose mastectomy, suggesting that surgical decisions are often driven by factors beyond extent of disease and treatment response.