Clinical outcomes of breast cancer patients treated in phase I clinical trials at University of Colorado Cancer Center

Patients with metastatic breast cancer (MBC) refractory to standard of care therapies have a poor prognosis. The purpose of this study was to assess patient characteristics and clinical outcomes for patients with MBC treated on phase I clinical trials. We performed a retrospective review of all patients with MBC who were enrolled in phase I clinical trials at the University of Colorado Cancer Center from January 2012 to June 2018. A total of 208 patients were identified. Patients had a mean age of 57 years and received on average 2.1 (range 0-10) prior lines of chemotherapy. The majority of patients had hormone receptor-positive/HER2-negative breast cancer (58.6%) and 30.3% had triple-negative breast cancer. The median progression free survival (PFS) was 2.8 months (95% CI, 2.3-3.9) and median overall survival (OS) was 11.5 months (95% CI, 9.6-13.2). Independent factors associated with longer PFS in multivariable analysis were treatment in a breast cancer-selective trial or cohort (p = 0.016), age >50 years (p = 0.002), and <= 2 prior lines of chemotherapy in the metastatic setting (p = 0.025). Phase I clinical trials remain a valuable option for select patients with MBC and enrollment should be encouraged when available.