Overall, 869, 882, and 853 patients with at least one SS diagnosis were identified in 2018, 2019, and 2020, respectively (Table 1). Patient characteristics were similar across the cohorts. Approximately 54–56% of patients were male, and the median age was 70 years in all three cohorts. The greatest proportion of patients was in the South, followed by the Northeast.

Overall, 64.6%, 67.7%, and 68.8% of SS patients had claims for at least one form of treatment in 2018, 2019, and 2020, respectively. Nearly 50% of patients had claims for systemic therapy in each year (Table 2). There was a numeric increase in patients receiving both systemic and SDTs, from 41.8 to 46.5% and 48.9 to 52.9%, respectively, between 2018 and 2020. The increase in systemic therapy was mainly driven by an increase in parenteral therapies, from 20.7 to 28.7% over the 3-year period. The increase in SDT appeared to be driven by an increase in topical therapy claims, from 42.3% in 2018 to 48.3% in 2020. Very few patients had BMT (≤ 1.5% per year).

The most common systemic therapies are illustrated in Fig. 1a. ECP was most common in 2018 and 2019. However, ECP utilization decreased from 40.8% in 2018 to 33.3% in 2019 and 29.0% in 2020. Utilization of bexarotene and brentuximab vedotin also decreased between 2018 and 2020. Following its approval in 2018, mogamulizumab use increased over time, becoming the second most used systemic therapy among SS patients with any systemic therapy in 2019 (24.5%) and the most used in 2020 (29.2%).

Systemic therapy rates. a Annual. b Quarterly. Percentages in a were calculated among patients treated with any systemic therapy. Patients with claims for multiple treatments will appear in multiple categories. The gray highlighting in b indicates the period in which COVID-19 impacts are most likely to have occurred. Percentages in b represent the number of patients with a claim in a given quarter divided by the total number of unique SS patients with a prescription for systemic therapy in that year. As such, quarterly treatment claims in b may not sum to the yearly treatment claims presented in Table 2. ECP extracorporeal photopheresis, IFN interferon, IV intravenous, SS Sézary syndrome

Parenteral systemic therapy use decreased from 11.6% in Q1 to 10.5% in Q4 of 2018; however, there was a progressive increase in usage observed from Q1 to Q4 in both 2019 and 2020 (15.3–16.9%, and 16.8–17.5%, respectively) (Fig. 1b). Parenteral systemic therapy was the most common systemic therapy (> 14%) in each quarter of 2019 and 2020, followed by ECP in 2019 (ranging from 9.9–11.0%) and oral systemic therapy in 2020 (ranging from 9.4 to 11.1%). Oral systemic therapy use decreased from 11.5% in Q1 to 9.4% in Q4 of 2018, remained relatively stable from 8.8% in Q1 to 9.0% in Q4 of 2019, and increased slightly from 10.2% Q1 to 11.1% in Q4 of 2020. Despite the increasing trend, there was a notable dip in utilization (9.4%) in Q2 2020, coinciding with the start of the COVID-19 pandemic. ECP usage decreased from Q1 to Q4 within each study year; similar to oral systemic therapy, there was a notable dip (8.4%) in Q2 2020.

Among the 853 patients diagnosed with SS in 2020, the five US states with the highest proportions of patients were Florida (13.1%), New York (10.7%), California (9.1%), Texas (6.7%), and Pennsylvania (5.6%). The proportion of patients with at least one form of treatment over 3 years in Florida, New York, Texas, and Pennsylvania ranged from 62.2 to 74.7%, with this being slightly lower in California (51.0–64.1%). SDT usage varied by state: New York had the highest utilization overall, ranging from 56.8% in 2018 to 59.3% in 2020; by contrast, there was a decrease in Texas from 49.1% in 2018 to 35.1% in 2020 (Fig. 2).

Annual treatment rates in the top five US states. Rates represent the number of patients in each state with a claim in each year divided by the total number of unique SS patients in each state in that year

Systemic therapy use increased over time in California (from 27.5% in 2018 to 42.3% in 2020) and New York (from 44.2% in 2018 to 50.5% in 2020). By contrast, usage increased from 2018 to 2019 but decreased from 2019 to 2020 in Florida (2018: 45.3%, 2019: 52.5%, 2020: 49.1%), Pennsylvania (2018: 43.2%, 2019: 57.1%, 2020: 52.1%), and Texas (2018: 49.1%, 2019: 51.9%, 2020: 49.1%). Overall, BMT was reported in very few patients, though again this varied (0–7.4%).

The five most commonly used systemic therapies are presented by state in Fig. 3. In Florida (Fig. 3a), ECP was the most common systemic therapy in all years (2018: 56.3%, 2019: 37.7%, 2020: 40.0%). Mogamulizumab was the second most common in 2019 (34.0%) and 2020 (29.1%). Treatment rates for bexarotene (2018: 18.8%, 2019: 9.4%, 2020: 12.7%), oral methotrexate (2018: 16.7%, 2019: 11.3%, 2020: 7.3%), and romidepsin (2018: 12.5%, 2019: 5.7%, 2020: 9.1%) decreased over time.

Most prescribed systemic treatments in the top five US states. a Florida, b New York, c California, d Texas, e Pennsylvania. Rates represent the number of patients in each state with a claim in each year, divided by the total number of unique SS patients with a prescription for systemic therapy in each state in that year. ECP extracorporeal photopheresis

In New York (Fig. 3b), bexarotene was the most common systemic therapy in 2018 (33.3%) and 2020 (30.4%) and the second highest in 2019 (27.8%) after ECP (30.6%). Mogamulizumab use increased from 2019 (19.4%) to 2020 (23.9%) to become the second most common systemic therapy. Treatment rates for oral methotrexate decreased over time (from 19.0% in 2018 to 8.7% in 2020), while romidepsin rates increased (from 7.1% in 2018 to 13.0% in 2020).

In California (Fig. 3c), romidepsin was the most common systemic therapy in 2018 (28.6%); however, mogamulizumab was most common in 2019 (30.0%) and 2020 (42.4%). Oral methotrexate usage increased from 21.4% in 2018 to 36.4% in 2020, whereas ECP usage decreased over time from 21.4% in 2018 to 6.1% in 2020. Bexarotene usage varied between years (2018: 7.1%, 2019: 15.0%, 2020: 9.1%).

In Texas (Fig. 3d), systemic treatment rates varied by year. In 2018, bexarotene was the most common (29.6%); however, rates decreased in 2019 (10.7%) and 2020 (10.7%). In 2019, romidepsin was most common (28.6%); in 2020, ECP was most common (35.7%). Overall, an increase in rates of ECP was observed from 2018 (22.2%) and 2019 (25.0%). Mogamulizumab usage was relatively low in 2019 and 2020 (10.7% and 10.7%, respectively) compared to other states. Oral methotrexate use remained low over time (from 0.0% in 2018 to 3.6% in 2020).

In Pennsylvania (Fig. 3e), ECP was the most common systemic therapy across all 3 years of the study (2018: 68.8%, 2019: 60.7%, 2020: 64.0%). Mogamulizumab was the second most common in 2019 and 2020 (25.0% and 24.0%, respectively). Bexarotene usage remained stable from 2018 (25.0%) to 2019 (25.0%); however, it decreased slightly in 2020 (20.0%). Romidepsin usage decreased (2018: 18.8%, 2019: 3.6%, 2020: 8.0%), and oral methotrexate use remained low over time (from 0.0% in 2018 to 4.0% in 2020).