Feasibility of active surveillance for atypical lipomatous tumors and impact on quality of life: interim analysis of the MINIMALIST trial

Background Atypical lipomatous tumors (ALTs) are low-grade soft tissue tumors with an excellent prognosis and small risk of dedifferentiation. Despite their indolent behavior, ALTs are often treated with surgery, which can cause substantial morbidity and risk of local recurrence. The aim of this study was to assess the safety and feasibility of active surveillance (AS) as well as health-related quality of life (HRQoL) in patients with ALT during 1 year of follow-up. Patients and methods In this prospective multicenter cohort study (MINIMALIST, NL72207.078.20), 50 patients with a primary or recurrent MDM2-confirmed ALT were included. Patients chose AS or surgery following standardized counseling. The AS protocol included regular clinical assessment and monitoring with magnetic resonance imaging to assess symptoms, tumor growth, and dedifferentiation. This prespecified interim analysis reports 1-year feasibility (>50% remaining on AS), safety (dedifferentiation in <5%), tumor progression rate, progression-free survival (PFS) and HRQoL during AS. Results Of the 50 patients included, 46 (92%) chose AS, whereas four (8%) opted for surgery. Among patients managed with AS, 38 (83%) patients remained on surveillance at 1 year and PFS was 89% at the 1-year follow-up. In most cases, debilitating symptoms were the reason for switching to surgery. None of the patients developed dedifferentiation during AS. HRQoL scores remained stable over 1 year in the AS group. Conclusion This interim analysis demonstrates that AS is feasible and seems safe in the majority of patients with ALT, with 83% remaining on surveillance after 1 year, no cases of dedifferentiation, and preserved HRQoL.