Abstract P2-14-04: Delayed initiation of adjuvant chemotherapy in older women with breast cancer
Authors: Smith-Graziani Demetria , Lei Xiudong , Giordano Sharon , Zhao Hui , Karuturi Meghan , Chavez-MacGregor Mariana 
Published: March 2020

Background: Early stage breast cancer patients benefit from adjuvant chemotherapy, but delays in initiation of treatment can negatively impact outcomes. Delays may be more common in older women. In this study we evaluate the survival impact of delays in adjuvant chemotherapy initiation in patients over 65 years of age and identify factors associated with delays.

Methods: Patients age 66 years and older diagnosed between 2001 and 2013 with localized or regional breast cancer were identified in the SEER-Medicare and Texas Cancer Registry-Medicare databases. All patients received adjuvant chemotherapy within 9 months of surgery. Patients were required to have continuous Medicare Parts A and B coverage and no HMO enrollment 12 months before and 12 months after diagnosis. We grouped patients according to time from surgery to chemotherapy in 4 groups: 0-30, 31-60, 61-90, and &gt; 90 days. Delayed chemotherapy initiation was defined as &gt; 90 days. We used multivariable logistic regression to identify predictors of delayed chemotherapy. We estimated overall survival (OS) and breast cancer-specific survival (BCSS) using Kaplan-Meier method. Inverse probability treatment weights were applied to survival analyses. Cox proportional hazard models were used to determine the association between delays in chemotherapy and outcome after adjustment for other variables.

Results: 25,902 women were included in the analysis, and the median age was 71 years. The median time from surgery to chemotherapy was 43 days. From 2001-2013 this interval increased from 38 days to 47 days (p &lt; 0.001). Chemotherapy delays were observed in 10.6% of the patients. In multivariable analysis, factors associated with an increased risk in chemotherapy delays included: older age, black or Hispanic race/ethnicity, being single, more comorbidities, hormone receptor positivity, mastectomy, Oncotype DX testing, and having a full state buy-in Medicare plan. Chemotherapy delay was associated with worse OS. The 5 year OS estimates for patients receiving chemotherapy 0-30, 31-60, 61-90 and &gt; 90 days after surgery were 0.82, 0.81, 0.80 and 0.73 respectively (p &lt; 0.001). A similar trend was seen with BCSS (p &lt; 0.001). After multivariable adjustment chemotherapy delay was associated with worse OS (HR=1.32, 95%CI 1.24-1.40) and BCSS (HR=1.38, 95%CI 1.24 - 1.52) compared with patients in the 0-30 day category. In a stratified analysis among patients with known breast cancer subtype, we observed that a delay in adjuvant chemotherapy initiation was associated with worse OS among patients with hormone receptor-positive (HR=1.45, 95%CI 1.05-2.01), HER2-positive (HR=1.52, 95%CI 1.03-2.23), and triple negative (HR=1.90, 95%CI 1.32-2.73) breast cancer.

Discussion: Delays in initiating adjuvant chemotherapy in older women with breast cancer are associated with worse OS and BCSS. Our data demonstrates that delays should be avoided and should encourage providers to initiate chemotherapy ≤ 90 days after surgery. In addition, the multidisciplinary medical team should be aware of the socioeconomic factors that may impact patients’ ability to receive timely treatment. Further studies should seek to elucidate the causes of these inequities in care.

Citation Format: Demetria Smith-Graziani, Xiudong Lei, Sharon Giordano, Hui Zhao, Meghan Karuturi, Mariana Chavez-MacGregor. Delayed initiation of adjuvant chemotherapy in older women with breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-14-04.