Incidence, prediction, and the long-term outcome of solid pseudopapillary tumor of the pancreas with malignant behaviors: a pooled-analysis

Abstract

Background: Microscopic malignancy or gross metastasis of solid pseudopapillary tumor of the pancreas were considered to be malignant behaviors. The clinical status of solid pseudopapillary tumors of the pancreas with malignant behaviors (SPTM) are unclear. This study was to perform a review and pooled-analysis to determine the incidence and predictors of SPTM, and explore the survival and prognostic factors.Methods: A registered meta-analysis (PROSPERO: CRD42020163788) was performed. Studies reporting on SPTM and follow-up information were identified between 1960 and 2020 by searching PubMed, Scopus, and Embase. The search process followed the PRISMA guidelines.Results: A total of 98 articles were included in this study, including 22 articles reporting the incidence of SPTM, and 159 SPTM cases containing survival information in 77 articles. Pooled estimates showed that the incidence of SPTM in solid pseudopapillary tumors of the pancreas was 22% [95% CI：19~24%], and tumor size ≥5 cm (OR: 2.03，95%CI: 1.28~3.22) was the only risk factor for predicting the occurrence of SPTM. The 5-, and 10-year survival rates of SPTM patients after complete surgical resection were 92% and 77%, respectively. Larger tumors (diameter ≥5cm) (p=0.046), lymphovascular invasion (p=0.005), lymph node metastasis (p=0.02), cellular atypia (0.018), Ki67 index ≥5% (p=0.001), tumor recurrence (p=0.004), recurrent time <5 years (p=0.005) and positive margin (p=0.003) were prognosis unfavorable factors for survival. Additionaly, lymphovascular invasion (OR:8.25, 95% CI:2.26-30.1), lymph node metastasis (OR:25.28, 95% CI:3.01-211.74), extrapancreatic invasion (OR:9.07, 95% CI:2.36-34.84), cellular atypia (OR:16, 95% CI:3-85.3), and Ki67 ≥5% (OR: 7.88, 95%CI: 1.53~40.51) increased the risk of recurrences of resected SPTM. Conclusion: Tumor size is an important factor in predicting the occurrence of SPTM before operation, and complete surgical resection can provide SPTM patients a expected long-term survival. Proved clinicopathological factors by current research will help to determine prognosis and recurrence, and close follow-up of five years or more after operation is essential.