Risk of non-breast cancer–related mortality in breast cancer and dependence on disease characteristics, treatment, and survival duration.

Abstract

12041 Background: Breast Cancer (BC) has seen significant improvement in survival in both early (eBC) and metastatic (mBC) setting. Prolonged survival increases the risk of acquisition of other comorbidities and result in non-BC related mortality (NBCRM). Purpose of this study is to identify the high-risk disease characteristics and trends for NBCRM. Methods: Patients (pts) with BC diagnosed as first primary malignancy between 2010-2019 were identified from 2023 release of SEER 17 database, with follow up till 12/31/2021. Causes of mortality were extracted and categorized as BC related mortality (BCRM) and NBCRM. BC related competing risk adjusted fine and gray regression model was used for survival analysis for NBCRM and subdistribution hazard ratio (SHR) is reported. Restrictive mean survival time (RMST) was calculated for pts with radiation and chemotherapy. Pearson chi-square tests used for comparison of categorical data. Results: 457,655 BC pts were identified. Median overall survival (OS) for mBC was 34 months (m) (95% CI 33-35 m) and not reached for eBC. For adjusted NBCRM, risk of mortality was higher for age ≥ 65 (eBC SHR 10.2, mBC SHR 2.5, Both p < 0.01) and age 51-65 (eBC SHR 2.5, mBC SHR 1.5, both p < 0.05) compared to age ≤ 50 years. Triple negative (TNBC) (eBC SHR 1.2, p < 0.05) had higher risk compared HR+/HER2- but not for mBC. For eBC, higher risk for Stage II (SHR 1.5, p < 0.05) and Stage III (SHR 2.0, p < 0.05) compared to Stage I. Lobular histology had lower risk of NBCRM for eBC (HR 0.86, p < 0.05) and no difference was seen for mBC (SHR 0.93, p = 0.27). Pts with radiation (RT) had lower risk of NBCRM (eBC SHR 0.57, mBC SHR 0.86, Both p < 0.05). RMST difference for Pts with RT vs no RT increased from 0.08 m at 1 year to 1.7 m at 5 years for eBC and 0.09 m at 1 year to 1.38 m at 5 years for mBC. Similarly, pts with chemotherapy (CT) had lower NBCRM (eBC SHR 0.52 p < 0.05, mBC SHR 0.7, p < 0.01). RMST difference for pts with CT vs no CT increased from 0.35 m at 1 year to 1.31 m at 5 years for eBC and 0.27 m at 1 year to 3.53 m at 5 years for mBC. Cardiovascular (CVS) (30.76%) and subsequent malignancies (19.96%) were most common causes of NBCRM for eBC. Of all CVS-mortality, 11% occurred < 1 year of diagnosis and 40% after 5 years. Subsequent solid malignancy- mortality was 6.8% in < 1 year and 41% for > 5 years. Subsequent hematological malignancy- mortality was 5.9% in < 1 year and 38% for > 5 years. For mBC, the above trends for NBCRM were inconclusive, given median OS was < 3 years. Conclusions: With the rising number of BC survivors, it is imperative to identify high-risk disease characteristics which can lead to NBCRM. Risk of NBCRM was noted to be related to age of diagnosis, stage, histology and treatment. Risk of CVS and subsequent malignancy related mortality was significantly more for pts surviving more than 5 years, especially in the eBC setting, highlighting the importance of adherence to preventive health guidelines and lifestyle modifications.