Healthcare Resource Utilization and Costs of Advanced Systemic Mastocytosis Among Medicare Fee for Service Beneficiaries

Systemic mastocytosis (SM) is a rare mast cell neoplasm driven by KIT D816V mutation. Advanced SM (AdvSM) includes three disease subtypes: aggressive SM, SM with associated hematological neoplasm, and mast cell leukemia. ¹ Advanced disease onset often develops in patients above the age of 60. ¹ Patients with AdvSM experience a range of severe symptoms including organ damage and shortened survival. ² There is limited research quantifying the impact of AdvSM on healthcare resource utilization (HCRU) and costs, particularly within the Medicare population. This retrospective study compared direct HCRU and costs in Medicare beneficiaries with AdvSM to a matched cohort of beneficiaries without SM.

This study used Centers for Medicare and Medicaid Services-sourced 100% Medicare Fee for Service (FFS) claims (Parts A/B/D) to identify newly diagnosed SM patients with >2 medical claims for SM (ICD-10-CM Dx codes: D47.02 OR C94.30 OR C94.31 OR C94.32 OR C96.21) between 01/01/2017 and 12/31/2018. The index date was the date of first observed SM diagnosis code. A claims-based algorithm was used to determine AdvSM subtype. Patients were required to have continuous enrollment in Medicare Parts A/B/D for 12 months pre- and post-index. AdvSM patients were direct matched (1:1) to a non-SM control cohort on age, sex, race, index year, Medicare-Medicaid dual eligibility, and Charlson Comorbidity Index score. HCRU and costs were assessed pre- and post-index. Chi-square and t-tests were used to evaluate differences in outcomes between AdvSM and non-SM patients. Medical costs are reported in 2021 USD.

After matching, there were 339 AdvSM and 339 non-SM patients. Mean [SD] age was 68.2 [13.2] among AdvSM and 68.5 [13.9] among non-SM patients. More than 25% of patients were <65 years old at index and qualified for Medicare due to a preexisting disability. Majority of patients were female (59%) and White (91%). Compared to non-SM patients, AdvSM patients had more specialist and emergency department (ED) visits during the baseline period. Baseline prevalence of asthma (26% vs. 16%, p=0.0009) and any malignancy (60% vs. 23%, p<0.0001) was higher among AdvSM patients compared to controls, and lower for hypertension (70% vs. 81%, p=0.0006), and diabetes with and without complications (28% vs. 52%; 16% vs. 33%; both p<0.0001).

During the 12 months post-index, all cause total healthcare expenditures (Parts A/B/D) were significantly higher for AdvSM patients than for non-SM comparator patients (mean [SD]: $123,412 [$180,386] vs. $47,988 [$64,693]; p<0.0001). Pharmacy costs (Part D) were a key driver of the total, accounting for 41% ($50,494 [$140,561]) of the total costs for AdvSM patients and 19% ($9,221 [$22,270]) of the total for non-SM patients. Inpatient hospital stays made up 24% of AdvSM patient costs and 26% of non-SM patient costs. More AdvSM than non-SM patients had ≥1 inpatient hospitalization (58% vs. 42%; p=0.0001), and length of hospital stay was significantly longer for AdvSM patients (13.1 [26.95] days) than for comparator patients (5.22 [12.66]; p<0.0001). Mean [SD] number of ED visits per patient was over twice as high for AdvSM than for non-SM patients (3.7 [12.0] vs. 1.6 [3.6]; p=0.0026). AdvSM patients had more than 5 times as many oncology/hematology and allergy/immunology physician office visits per patient versus non-SM controls (10.9 [21.5] vs. 2.0 [7.2]; 2.3 [7.4] vs. 0.1 [0.7]; both p<0.0001). AdvSM patients were higher utilizers of epinephrine (29.2% vs. <3% non-SM patients; p<0.0001), oral and systemic corticosteroids (54.0% vs. 38.1%, p<0.0001; 51.9% vs. 41.6%, p=0.0071), chemotherapy (12.09% vs. 6.78%; p=0.0181), and omalizumab (4.7% vs. 0.0%, p<0.0001).

AdvSM Medicare FFS patients were more resource intensive and had 2.5 times higher per-patient healthcare costs in the 12 months following SM diagnosis compared to a matched cohort of non-SM patients. These costs were driven by significantly higher rates of inpatient stays, more frequent ED and physician outpatient visits, and higher utilization of multiple medications. Notably, AdvSM patients in this analysis included a larger proportion of patients <65 years old with preexisting disability compared to the broader Medicare population (~25% vs. 14%), suggesting that AdvSM patients may be more likely to qualify for Medicare due to disability rather than age compared to the overall Medicare population. Further research in this area is warranted.