Abstract
For patients with breast cancer, delays in chemotherapy initiation have been adversely associated with recurrence and survival. We evaluated patient-level factors associated with delayed chemotherapy initiation, from both diagnosis and surgery, in a community-based cohort of women with early-stage breast cancer. For the Optimal Breast Cancer Chemotherapy Dosing study, we identified a cohort of 34,109 women diagnosed with stage I-IIIA breast cancer at two U.S. integrated healthcare delivery systems between 2004 and 2019. We used logistic regression to calculate odds ratios (OR) and 95% confidence intervals (CI) to identify patient factors associated with delays in chemotherapy initiation after diagnosis (≥90 days) and surgery (≥60 days). Among 10,968 women receiving adjuvant chemotherapy, 21.1% experienced delays in chemotherapy initiation after diagnosis and 21.3% after surgery. Older age, non-Hispanic Black and Hispanic race and ethnicity, and ER+ and/or PR+ disease were associated with increased likelihood of delays to chemotherapy initiation after diagnosis and surgery. People diagnosed in 2012-2019 (vs. 2005-2011), with a higher grade and larger tumor size were less likely to experience delays. Other factors were associated with a higher likelihood of delays specifically from diagnosis (earlier stage, mastectomy vs. breast-conserving surgery), or surgery (higher comorbidity, increased nodal number). Women diagnosed with breast cancer who were at highest risk of progression and recurrence were less likely to experience delays in chemotherapy initiation after diagnosis and surgery. Understanding reasons for chemotherapy delays beyond patient factors may be potentially important to reduce risk of breast cancer recurrence and progression.