Treatment patterns and health care costs for patients with psoriatic arthritis on biologic therapy: a retrospective cohort study

Background: Biologic therapies have been used in patients with psoriatic arthritis (PsA) who have been inadequately treated with conventional disease-modifying anti-rheumatic drugs (DMARDs).

Objective: Examine treatment patterns and health care costs among patients with PsAs who initiated biologic therapy either as monotherapy or adjunctively with traditional DMARDs.

Methods: The MarketScan(®) database was used to identify adults with PsA who initiated therapy with a biologic (with first use identified as index date). Patients were required to have a 6-month pre-period with no biologic use and 1 year insurance eligibility pre- and post-index date. Cohorts of patients initiating biologic therapy either as monotherapy or adjunctively with traditional DMARDs were created. Medication use patterns including discontinuation, switching, and restarting were identified during the 1-year follow-up period. Cox proportional hazards models were conducted to compare time to discontinuation of index biologic, and logistic models were used to compare the rate of discontinuation and biologic switching between the 2 cohorts. All-cause and PsA-related costs were compared between the 2 cohorts using propensity score-adjusted bootstrapping methods. All comparisons were made after adjusting for age, sex, Charlson comorbidity index, and PsA-related total cost over 1-year pre-index date.

Results: Among the 3164 PsA patients identified, 67.7% initiated biologics as monotherapy and 32.3% initiated biologics adjunctively with traditional DMARDs. The number of patients on pain medications, topical medications, and traditional DMARDs was significantly lower post index date compared to pre-index date (P < 0.01), while use of antihypertensives, antidiabetics, and statins increased after patients initiated biologic therapy. In 1-year post-period, approximately half of the patients (50.9%) who initiated a biologic continued their index biologic with an average time to discontinuation of 279.8 days for all patients. Rates of discontinuation, switching, and restart were 33.1%, 9.9%, and 6.1%, respectively, for all patients. Rates of switching and restart were similar between the 2 cohorts, but a significantly lower rate of discontinuation was observed in the biologic plus traditional DMARDs cohort than the biologic monotherapy cohort. Pharmacy expenditures were higher for the biologic + DMARD cohort than the biologic-monotherapy cohort ($14,486 vs $14,062; P = 0.0348). No statistically significant differences for either all-cause or PsA-specific costs were observed across the treatment cohorts.

Conclusions: Traditional DMARDs used in combination with biologic therapy appear to reduce rates of biologic therapy discontinuation.