A large global registry study is shedding new light on how to best treat mycosis fungoides (MF) and Sézary syndrome (SS) — two rare but serious cutaneous T-cell lymphomas. Data from the PROCLIPI registry, which spans six continents and follows over 2,000 patients (509 with advanced-stage disease), show that combining and sequencing available therapies can push the time to next treatment into the 18–20 month range — a meaningful win for a disease with no accepted standard of care.

Among first-line options, extracorporeal photopheresis (ECP) delivered the longest median time to next therapy at 19 months, while gemcitabine posted the highest response rate at 78%. Combination regimens consistently outperformed monotherapy — for example, ECP in combination extended time to next treatment from 14.6 to 20.3 months. In the second-line setting, mogamulizumab led with a 79% response rate, and ECP again topped durability charts at 19.3 months.

Key Takeaways:

• Combination therapy consistently outperforms monotherapy across agents including ECP, methotrexate, interferon alpha, and bexarotene
• A 4-month objective response rate (ORR4) to mogamulizumab predicts better 2-year overall survival (76% vs. 60%) and progression-free survival (58% vs. 35%)
• Skin rash during mogamulizumab treatment may signal a stronger clinical response
• Dermatologist-led options such as phototherapy and electron beam therapy remain central throughout the disease course, even alongside systemic therapy

Why it matters: With no standard of care established for advanced MF/SS, real-world sequencing data like these are critical for guiding clinicians. The findings reinforce that dermatologists should remain central to care even in advanced stages, and that smarter sequencing — not just drug selection — can meaningfully extend patient outcomes.