Factors associated with CDK 4/6 inhibitor use for patients with advanced, hormone positive, HER-2-negative breast cancer.

Abstract

e13038 Background: “CDK4/6 inhibitors have emerged as a standard of care for patients with HR-positive, HER2-negative advanced breast cancer.” Wayne Kuznar ASCO Reading Room 10.29.2019. Within an academic institution there were concerns that CDK 4/6 inhibitors were not utilized as indicated. We conducted an analysis of CDK 4/6 inhibitor use for patients with advanced, hormone positive, HER2 negative breast cancer to assess factors associated with CDK 4/6 inhibitor use. Methods: We conducted a retrospective medical records review of patients treated at an academic medical center from 01/1/2015 to 9/30/2020 with stage IV, hormone positive and HER2 negative breast cancer. We compared characteristics for patients that received one or more CDK 4/6 inhibitors to those who did not receive any CDK 4/6 inhibitors. Statistical analysis used Fishers exact 2-sided test via GraphPad QuickCalcs website. Results: 162 patient records met inclusion criteria, 73% (119/162) received one or more CDK 4/6 inhibitors as part of their care. The average age of patients who received CDK 4/6 inhibitors was 59.9, as compared to 66.9 average age in patients who did not receive CDK 4/6 inhibitors. Patients who received CDK 4/6 inhibitors were more likely to have received chemotherapy (Table, p < 0.0001), have a family history of cancer (p < 0.0001) and have a Charlson comorbidity index of 5 or more (p = 0.0005). Patients receiving CDK 4/6 inhibitors trended more likely to have used tobacco at some point (p = 0.09). Patients who did not receive CDK 4/6 were more likely to have refused, moved or be in hospice (p = 0.003). There were no statistically significant differences based on patient status, timing of diagnosis or timing of first hormone receptor positive dose. Further analysis of the 27% (43/162) of patients not receiving CDK 4/6 inhibitors identified that 40% (17/43) died, 28% (12/43) had Charlson comorbidity score of 7 or more, 19% (8/43) refused treatment. The remaining 14% (6/43), 4% (6/162) of entire population, did not have a clear reason for not getting CDK 4/6 inhibitors, of those 4 received hormone therapy, 1 received chemotherapy and 1 received both. Conclusions: In a retrospective analysis of patient records, we found consistent use of CDK 4/6 inhibitors for indicated patients. Patients who did not receive CDK 4/6 inhibitors died, had a high co-morbidity index, or refused treatment. Only 4% of the population analyzed did not have a visible reason to not receive CDK 4/6 inhibitors.[Table: see text]