Treatment modalities for advanced solid pseudopapillary tumor of the pancreas.

Abstract

e16327 Background: Solid pseudopapillary tumor (SPT) of the pancreas is a rare low-grade malignant tumor. However, a minority of SPT patients present aggressive behavior and develop recurrent or metastatic diseases. The treatment strategies of advanced SPTs remain unclear. Our study aimed to explore the treatment modalities of aggressive SPTs and the role of endocrine therapy. Methods: The data on clinicopathologic characteristics and treatment of advanced SPT patients from Sun Yat-Sen University Cancer Center and Shen Zhen People's Hospital were collected. The treatment modalities were explored by co-analyzing our local cohort and published literatures. Single sample gene set enrichment analysis (ssGSEA) was used to explore the functional enrichment pathway (GSE43795). Fresh surgical specimens from 10 SPT patients were collected for endocrine drugs sensitive test in vitro by performing tumor histoculture end-point staining computer image analysis (TECIA). Results: A total of 77 advanced SPT patients including 14 cases in our local cohort and 63 cases from published literatures were enrolled. 60 patients received local treatment including cytoreductive surgery, interventional therapy or radiation therapy. 55 patients who had undergone cytoreductive surgery have better outcome compared with others (P = 0.046, HR = 4.12). 31 patients received systemic chemotherapy and 6 patients received targeted therapy. There were 2 patients achieved partial response after chemotherapy. In our local cohort, 5 patients received endocrine therapy with tamoxifen plus megestrol. One patient achieved partial response with duration of response (DOR) of 89 months. 4 patients showed stable disease. ssGSEA for GSE43795 showed that Wnt signaling pathway and its inhibitory pathway-progesterone receptor signaling pathway were simultaneously enriched in SPTs. The results of endocrine drug sensitive test in vitro by TECIA showed response rate of 50% (5/10) in megestrol group, 40% (4/10) in tamoxifen group, and 30% (3/10) in testosterone propionate group. Conclusions: Advanced SPTs did not appear chemosensitive. Cytoreductive surgery may improve survival. Simultaneously enriching Wnt and progesterone receptor signaling pathway may partially explain the low aggressive ability of SPT and their unbalance may lead to the aggressive behavior of SPT. Endocrine therapy with tamoxifen plus megestrol, by enhancing the progesterone signaling pathway, seems to be a promising regimen for advanced SPTs, which is worth to be noted and further studied.