Citations

e12522 Background: Trastuzumab is widely used in management of HER2+ breast cancer patients. A known adverse effect of trastuzumab use is cardiac dysfunction, which can often be reversed with cessation of therapy. Our objectives were to 1) assess if trastuzumab can be safely administered to breast cancer patients with reduced cardiac function and 2) identify patient characteristics that predict susceptibility to trastuzumab-induced cardiac dysfunction. Methods: A retrospective analysis was performed on female patients seen at Mayo Clinic for HER2+ breast cancer and treated with trastuzumab for localized or metastatic disease between January 1, 2000 and August 31, 2015. Eligibility criteria included documentation of and results from at least one echocardiogram prior to and at least one after trastuzumab initiation. Left ventricular (LV) ejection fraction (EF) of 53% or more was considered normal. Any LVEF reduction of 10% or more was considered significant. Among patients with normal EF, age strata of < 45, 45-60, and > 60 at time of trastuzumab initiation were used to assess risk factors for clinically diagnosed cardiac dysfunction (defined as EF < 53 or abnormal strain and physical symptoms of heart failure (HF)). Results: We identified 335 women (mean age 53.3, with 25.3% age < 45, 44.5% age 45-60, and 30.1% age > 60) who had normal LVEF (median EF 64, range: 53-75) and 23 women (mean age 53.4, with 30.4% age < 45, 43.5% age 45-60, and 26.1% age > 60) who had low LVEF at baseline (median EF 52, range: 25-52). Approximately a third (34.3%) of women with normal LVEF prior to initiation of therapy had at least one subsequent echocardiogram showing a drop of 10% or a low LVEF ( < 53). Approximately a quarter (26%) of women with low LVEF at baseline had a 10% drop in LVEF. HF incidence increased with age. Predictive factors for trastuzumab-induced cardiac dysfunction were obesity and history of coronary artery disease (CAD) across all age strata, and chest irradiation (IR) for those aged 45-60 only. Conclusions: Our results suggest that trastuzumab can be administered in women with reduced cardiac function at no greater risk than in those with preserved cardiac function. Some women with no obesity, history of CAD, or history of chest IR may not need echocardiograms during trastuzumab therapy.

531 Background: The greatest age disparity in early stage breast cancer (BC) outcomes is in young women with hormone receptor positive (HR+) BC. While differences in biology may play a role, understanding the role of non-persistence (early discontinuation) with endocrine therapy (ET) is critical given the demonstrated efficacy of ET in this population. Methods: As part of a prospective cohort that enrolled women with BC diagnosed (dx) at age ≤40 between 2006-2016, we identified women with HR+, Stage I-III BC. Socio-demographic and treatment information, fertility concerns and confidence with the ET treatment decision were assessed by survey within 1 yr of dx. Medical record review was used to ascertain stage and HR status. Women who initiated ET but did not report taking tamoxifen or an aromatase inhibitor at 3 yrs post-diagnosis (or last follow-up if <3 yrs) were classified as non-persistent. Chi-square tests were used to compare categorical variables between persisters and non-persisters and stepwise multivariable regression to evaluate predictors of non-persistence. Results: In 538 women who initiated ET, median age at dx was 36; 10% were non-persistent. Discontinuation of ET was more likely in those who were less confident with their ET decision compared to those who were more confident (25/179, 14% vs 18/263, 7%, p=0.01). A greater proportion of women concerned about fertility discontinued vs. women not concerned (29/213,14% vs 25/319, 8%, p=0.03), and fertility concerns were associated with non-persistence in multi-variable analyses (OR: 1.85, 95% CI 1.05-3.26, p=0.03). Age at dx, race, education, employment, financial comfort, marital status, parity, stage, chemotherapy and local therapy were not associated with non-persistence. Conclusions: A significant minority of women with HR+ BC discontinued ET within 3 yrs. The association between fertility concerns expressed soon after dx and non-persistence underscores a need to address psychosocial issues that can impact treatment decisions in young women. Strategies to reduce decisional conflict and increasing confidence with the choice to take ET, may influence persistence. Future work will evaluate the contribution of other factors (eg symptom burden) to non-persistence.

526 Background: Young age at diagnosis (dx) is a predictor of worse prognosis in patients (pts) with luminal breast cancer (BC). Poorer adherence to endocrine therapy (ET) among younger women may contribute to this disparity. Aim: To assess non-adherent behaviors and associated factors among young women with stage 1-3 hormone receptor (HR)+ BC taking ET. Methods: This study is a part of a multi-center, prospective cohort of pts with dx of BC at or under age 40. On a survey 30 months after dx, among pts reporting taking ET, adherence was measured using a 3-item Likert-type scale (Do you ever forget to take your ET? If you feel worse when you take your ET, do you stop taking it? Did you take your ET exactly as directed by your doctor?). Pts reporting any non-adherent behavior during the last 3 months were classified as non-adherers. Variables with a p-value <0.20 were included in a multivariate logistic model. Results: Among361 pts eligible for this analysis, 174 (48%) reported some non-adherent behaviors in the last 3 months; 56 (16%) moderate or greater non-adherent behaviors. None of the studied variables was associated with non-adherent behaviors (table). Conclusions: Non-adherent behaviors to ET are present in almost half of the young women with HR+ BC. Further analyses of explanatory factors and impact of non-adherence are required to understand and potentially improve this problem. [Table: see text]