Healthcare Resource Utilization and Costs of Medicare Fee for Service Beneficiaries Newly Diagnosed with Moderate to Severe Non-Advanced Systemic Mastocytosis

Systemic mastocytosis (SM) is a rare mast cell disease driven by the KIT D816V mutation in which mast cells accumulate in ≥1 tissues or organs resulting from clonal proliferation of abnormal mast cells in one or more extracutaneous organs. Most forms of SM are non-advanced (non-AdvSM). To date, the economic burden of non-AdvSM has not been well-studied among Medicare patients. This study compared direct healthcare resource utilization (HCRU) and healthcare costs in Medicare beneficiaries with non-AdvSM and a matched cohort without SM.

This study used Centers for Medicare and Medicaid Services-sourced 100% Medicare Fee for Service (FFS) claims (Parts A/B/D) and identified newly diagnosed non-AdvSM patients who had ≥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 1/1/2017 and 12/31/2018. Patients were classified as non-AdvSM using a claims-based algorithm. The index date was the date of first observed SM diagnosis. Continuous enrollment in Medicare Parts A/B/D for 12 months pre- and post-index was required. Non-AdvSM patients were direct matched (1:1) on age, sex, race, index year, Medicare-Medicaid dual eligibility, and Charlson Comorbidity Index score to a non-SM control cohort. HCRU and costs were assessed during the 12 months pre- and post-index. Medical costs are reported in 2021 US dollars.

Post match, there were 333 non-AdvSM and 333 non-SM patients. Mean [SD] age of the non-AdvSM cohort was 67.3 [11.7] and 67.8 [13.3] years for the control cohort. Over 25% of patients were <65 years of age at index and originally qualified for Medicare with a disability. Most (76%) patients were female, and 94% were White. During the 12-month pre-index period, non-AdvSM patients had more specialist physician office visits per patient (mean [SD]: 15 [15]) compared to non-SM patients (10 [13]; p<0.01). Non-AdvSM patients vs. controls had higher prevalence of asthma (29% vs. 15%, p<0.0001) and any malignancy (43% vs. 15%, p<0.0001) and lower prevalence of hypertension (58% vs. 68%, p=0.0103), diabetes with and without complications (19% vs. 34%; 8% vs. 15%; both p<0.0001), and renal disease (7% vs. 11%, p=0.0439). Non-AdvSM patients were also higher utilizers of corticosteroids (64% vs. 54%, p=0.0094), epinephrine auto-injectors (31% vs. 1%, p<0.0001), and omalizumab (6% vs. 0%, p<0.0001) compared to non-SM patients.

Total (Parts A/B/D) healthcare costs in the 12-month follow up period were almost one-third higher for non-AdvSM patients than for non-SM controls (mean [SD]: $40,250, [$54,563] vs. $30,013 [$51,235]; p=0.0128). Pharmacy (Part D only) expenditures were also significantly higher ($13,938[$38,367] vs. $5,745 [$17,213], p=0.0004) and accounted for a greater proportion (34.6% vs. 19.1%) of total costs for non-AdvSM patients vs. non-SM patients. Non-AdvSM patients were high utilizers of physician office visits post-index compared to non-SM controls; more non-AdvSM patients had ≥1 oncology/hematology visit (36.9% vs. 12.9%; p<0.0001), or allergy/immunology visit (47.2% vs. 3.9%; p<0.0001) and mean [SD] visits per patient were higher among non-AdvSM patients (3.4 [11.8] vs. 1.3 [6.4] oncology/hematology, p=0.0049; 3.3 [9.5] vs. 0.2 [1.7] allergy/immunology, p<0.0001). Approximately 40% of non-AdvSM patients filled ≥1 prescription for an epinephrine auto-injector compared with <3% in non-SM patients (p<0.0001). More non-AdvSM patients had prescriptions for H1 antihistamines (13.8% vs. 5.4%, p=0.0002), oral and systemic corticosteroids (39.0% vs. 27.9%, p<0.0001; 51.7% vs. 32.1%, p=0.0079, respectively), leukotriene antagonists (40.5% vs. 8.7%; p<0.0001), and omalizumab (6.9% vs. 0.0%, p<0.0001).

Compared to a matched cohort of non-SM Medicare FFS patients, non-AdvSM Medicare patients had 30% higher mean per patient total healthcare expenditures ($40,250 vs. $30,013), driven by more prescription drug use and higher utilization of outpatient resources, specifically visits to oncologists/hematologists and allergists/immunologists. Notably, this analysis does not represent the HCRU and costs of the most severe SM patients. Further research to understand the basis of the higher proportion of non-AdvSM patient in this analysis who were <65 years and qualified for Medicare with a disability (vs. 14% in all of Medicare), and the corresponding long-term medical costs among these patients is warranted.