OBJECTIVES: To evaluate chronic conditions as leading predictors of economic burden over time among older adults with incident primary MCC.

METHODS: We used a retrospective analysis of SEER-Medicare data of older adults(age ≥ 67 years) diagnosed with MCC between 2009 and 2019 with three phases (pre cancer, treatment, and post treatment) anchored around cancer diagnosis date. All three phases had 12 months baseline and 12-months follow-up periods. The chronic conditions were identified in baseline and follow-up periods. The economic burden in terms of annual total (Medicare payments) and out-of-pocket(OOP) healthcare expenditures expressed in 2019$ were measured during 12-month follow-up periods. XGBoost regression models and SHapley Additive exPlanations methods were used to identify leading predictors and their associations with economic burden.

RESULTS: Congestive heart failure(CHF), chronic kidney disease(CKD) and depression had the highest average incremental total expenditures during pre-diagnosis, treatment, and post-treatment phases respectively($25,004,$24,221, and $16,277(CHF); $22,524,$19,350,$20,556 (CKD); and $21,645, $22,055, $18,350(depression)). Whereas the average incremental OOP expenditures during the same periods were: $3703,$3,013, $2,442(CHF); $2,457,$2,518, $2,914(CKD); and $3,278, $2,322, $2,783(depression). Except for hypertension and HIV, all chronic conditions had higher expenditures compared to those without the chronic conditions. Across all three phases, CHF, CKD, and heart diseases were among the top 10 leading predictors. The root mean square error(RMSE) ranged from as low as 0.63(pre during treatment) to as high as 1.05(pre-diagnosis) for total expenditures, and from 0.52(during treatment ) to 0.8(pre-diagnosis) for OOP suggesting modest predictive performance. Although CHF, CKD, heart diseases was among the top common 10 leading predictors of total and OOP expenditures, their feature importance ranking declined over time.

CONCLUSIONS: Among older adults with MCC, cardiac and renal conditions were the leading drivers of total expenditures and OOP expenditures. Our findings suggest that managing cardiac and renal conditions may be important for cost containment efforts.