Comparison of Risk Stratification Models to Predict Recurrence and Survival in Pleuropulmonary Solitary Fibrous Tumor

Introduction: Solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms. Most follow a benign course, but a subset will recur or metastasize. Various risk stratification schemes have been proposed for SFTs, but none has been universally endorsed and few have focused on pleuropulmonary SFTs. Methods: Histologic sections from surgically resected pleuropulmonary SFTs were examined, with confirmatory immunohistochemistry. Patients were risk-stratified by using four prediction models as proposed by de Perrot, Demicco (original and modified), and Tapias. Kaplan-Meier analysis was used to estimate overall survival (OS) and progression-free survival (PFS). Results: The 147 study patients included 78 females (53.1%) with a median age of 61.5 years (range 25–87). The median follow-up was 5.5 years (range 0–33). Recurrence or metastasis occurred in 15 patients (10.2%), with five deaths from disease. Significant predictors of worse OS included male sex, age at least 55 years, tumor size at least 10 cm, nonpedunculated growth, severe atypia, necrosis, and mitotic count of at least four per 10 high-power fields. Predictors of recurrence included tumor size of at least 10 cm, severe atypia, necrosis, at least four mitoses per 10 high-power fields, and Ki67 labeling index of at least 2%. All systems predicted PFS, but only the Demicco and Tapias systems significantly predicted OS. The modified Demicco system provided the best discrimination for PFS (C-statistic = 0.80 compared with 0.78). Conclusion: The risk scoring systems proposed by Tapias et al. and Demicco et al. were both predictive of OS and PFS. The Demicco system has the advantages of simplicity and applicability to SFTs from other sites, as well as provision of the best discrimination for PFS, and thus may be the best system to apply in general practice.