The relationship between treatment intensity and characteristics of patients with early-stage breast cancer.

Abstract

125 Background: Clinical trials are used to generate standard-of-care, yet often do not reflect patient populations treated in real-world settings. Elderly patients or patients of color who are often underrepresented in trials, which may impact what types of treatments are prescribed. This study examines how patient characteristics are associated with treatment intensity in early stage breast cancer. Methods: This retrospective cross-sectional study included women with a stage I-III breast cancer from American Society of Clinical Oncology’s CancerLinQ database treated by chemotherapy from 2005-2019. Seven standard-of-care regimens were characterized by intensity. For patients with ER+/- HER2- breast cancer, low-intensity regimens were Taxol and Cyclophosphamide or Adriamycin and Cyclophosphamide; while Taxol, Adriamycin, and Cyclophosphamide was considered high intensity. For patients with HER2+ breast cancer, the low intensity regimen was Taxol and Herceptin; while Adriamycin and Cyclophosphamide followed by Taxol and Herceptin; Taxol, Carboplatin, and Herceptin; or Taxol, Carboplatin, Herceptin, and Pertuzumab were considered high intensity. A model estimating the likelihood of intensity was calculated using log-binomial regression, in order to produce relative risks. The models were adjusted for patient demographics and cancer stage. Results: Of 24,383 patients, 51% had ER+HER2-, 20% ER-HER2-, and 29% HER2+ breast cancer. Most patients were White (60%), age 40-69 (80%), had stage II breast cancer (39%), and received higher intensity treatment (65%). Adjusted for the other covariates, patient who were Black were more likely to receive high-intensity treatment than patients who were White (61% vs 58%; RR 1.05, 95%CI 1.02-1.06. Additionally, older adults were more likely to receive low-intensity treatment, with 42% of patients over 70 receiving low intensity treatment, and 29% of patients between the ages 40 and 69 received low intensity treatment (RR 1.5, 95% CI 1.44 -1.54). Conclusions: Differences in treatment intensity were observed for patients with differing demographic characteristics. Further research is needed to determine lack of representation in clinical trials impacts on prescribing patterns, regimen intensity, and survival.