OBJECTIVES: Many United States (US) cost-effectiveness and budget impact models of oncology treatments source Grade 3/4 adverse event (AE) costs from HCUPnet, a public website query tool for the National Inpatient Sample (NIS) of the Healthcare Cost and Utilization Project (HCUP). Recently, HCUPnet has shifted from allowing users to identify hospitalization costs and length of stay (LOS) via detailed diagnosis codes (International Statistical Classification of Diseases 10^th Revision [ICD-10]) to only allowing broader categories not useful for parameterizing costs in economic models. We sought to estimate Grade 3/4 AE costs.

METHODS: The most commonly reported Grade 3/4 AEs were identified from the prescribing information (PI) for all Food and Drug Administration (FDA) approved novel therapies for an oncology indication in 2023. Selected AEs were mapped to ICD-10 codes. Accounting for survey and sampling design, weighted hospitalization costs and LOS were calculated for each code from the most recent NIS dataset available (2020) using R.

RESULTS: Twelve novel therapies were approved by the FDA in 2023 for oncology indications. Twenty-nine Grade 3/4 AEs were reported in the PIs of ≥4 treatments. Fatigue, decreased lymphocyte count, and decreased hemoglobin were the most reported (11/12) followed by musculoskeletal pain, decreased neutrophil count, decreased potassium, and increased alanine aminotransaminase (all 10/12). Survey weighted means and standard errors were calculated for each mapped ICD-10 code. Cytokine release syndrome was the most expensive and had the longest LOS; however, sample size was too low for reliable estimates. Of AEs with reliable estimates, total hospitalization costs (2020 US$) ranged from $6,032 for increased creatinine to $15,292 for decreased neutrophil count. LOS (days) ranged from 2.31 for headache to 5.48 for decreased appetite.

CONCLUSIONS: Many AEs of oncology treatments are common across recent approvals. Costs and LOS reported may be useful in parameterizing future economic models.