OBJECTIVES: This study described hospitalization costs of grade 3/4 all-cause adverse events (AEs) and treatment-related AEs (TRAEs) of nivolumab plus relatlimab fixed-dose combination therapy (Nivo+Rela) and nivolumab monotherapy (Nivo) for unresectable or metastatic melanoma.

METHODS: Rates of all-cause AEs and TRAEs associated with Nivo+Rela or Nivo between first dose and 30 days after last dose (i.e., study period) were calculated using patient-level data from the RELATIVITY-047 trial (NCT03470922; October 2021 database lock). Hospitalization costs of grade 3/4 AEs were included. AE unit costs were obtained from the US Healthcare Cost and Utilization Project (HCUP) National Inpatient Sample (NIS) database and inflated to 2021 USD. Per-patient-per-month (PPPM) AE costs were calculated as total costs divided by the total person-months at risk. Cost difference was calculated between the average costs for Nivo+Rela and Nivo. Top cost-driver AE categories were identified for each treatment.

RESULTS: The per-patient cost difference between Nivo+Rela and Nivo was $1,839 for all-cause AEs and $494 for TRAEs during study period (median follow-up: 19.3 months). The two arms followed similar trends of AE costs: all-cause AE PPPM costs were highest in the first 6 months, decreased during Year 1, and plateaued through Year 2 and 3, whereas TRAE costs were stable throughout the study. Nivo+Rela had slightly higher all-cause AE and TRAE costs than Nivo, especially in the first year. Top TRAE cost-driver categories were laboratory investigations ($461), gastrointestinal disorders ($264), and endocrine disorders ($208) for Nivo+Rela, accounting for 40% of costs; and blood and lymphatic system disorders ($612), skin and subcutaneous tissue disorders ($244), and laboratory investigations ($216) for Nivo (58% of total costs).

CONCLUSIONS: The AE cost trends over the study period were similar for the Nivo+Rela and Nivo arms, with slightly higher cost associated with Nivo+Rela. This analysis suggests minimal incremental economic burden associated with AE management for Nivo+Rela.