Treatment of metastatic solid pseudopapillary neoplasms

Abstract Background Surgical resection is the primary treatment for solid pseudopapillary neoplasms (SPN). Systemic treatment options are limited; no prospective trials or consensus guidelines exist given the rarity of SPN. Patients and Methods We retrospectively reviewed patients treated for SPN at Memorial Sloan Kettering Cancer Center from 2009-2024, summarizing demographics, treatments, outcomes, and genetic testing results when available. Results Of 45 patients, 42 (93%) underwent surgical resection and 8 (18%) received systemic or locoregional treatment (average 3.25 therapies per patient). Genetic testing was available for 10 patients (22%), 9 of whom had Wnt/β-catenin pathway alterations. One patient whose tumor harbored a CTNNB1 mutation was treated with an investigational therapy inhibiting β-catenin, achieving disease control for 7 months. Conclusion This is the largest single-institution series of treatment of advanced SPN, demonstrating that select therapies can provide disease control. Molecular characterization of SPN frequently identifies Wnt/β-catenin pathway alterations, demonstrating a potential clinical benefit for drugs targeting this pathway.