Abstract
PURPOSE: To evaluate economic outcomes in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer (mBC) treated with a first- or second-line cyclin-dependent kinase 4/6 inhibitor (CDK4/6i). METHODS: This retrospective analysis utilized Optum's Clinformatics DataMart (January 1, 2014-September 30, 2021). Included patients had ≥1 pharmacy claim for palbociclib, abemaciclib, or ribociclib in first or second-line and ≥6 months of continuous health plan enrollment in preindex (index: date of first CDK4/6i claim) and follow-up periods. Mean all-cause per patient per month (PPPM) medical, healthcare resource utilization (HCRU) and costs, and outpatient pharmacy prescriptions costs were compared among CDK4/6is using stabilized inverse probability of treatment weighting (sIPTW). RESULTS: We identified 3,182 patients taking palbociclib, 286 taking abemaciclib, and 149 taking ribociclib, with median follow-ups of 20.8, 16.6, and 19.9 months, respectively. After sIPTW, palbociclib was associated with a lower risk of inpatient (IP) admissions versus abemaciclib (35.8% vs 41.6%; odds ratio: 1.31; P=0.034). No other significant differences were seen for HCRU. PPPM outpatient costs were significantly lower with palbociclib versus abemaciclib ($754; P=0.05). PPPM IP ($2,252 vs $6,286), medical ($6,948 vs $11,717), and total ($19,370 vs $23,639) costs were also lower with palbociclib versus abemaciclib, although not significant. There were no significant differences in PPPM HCRU or costs between palbociclib and ribociclib. In patients with Medicare, PPPM total medical costs were lower with palbociclib versus abemaciclib by $1,608 (P=0.04), while other costs were not significantly different. No significant differences in costs were seen with palbociclib versus ribociclib. CONCLUSION: All-cause HCRU and costs were generally not different between the CDK4/6is but favored palbociclib for medical (including IP) costs versus abemaciclib. Due to limited patient numbers, uncertainty exists about abemaciclib and ribociclib cost estimations. Further studies of HCRU and costs are needed to support a cost-minimizing strategy for mBC.