Estimation of the amount of tumor stroma as a prognostic factor for pancreatic cancer using FDG-PET

Abstract:ObjectiveFDG-PET provides quantitative information regarding the tumor glucose metabolism which is useful for theclinical diagnosis of tumor diseases. It is said that the amount of tumor stroma correlates with prognosis ofpatients with cancer. FDG accumulates in cancer cells but does not accumulate so much in stroma tissues.So cancer tissue with abundant stroma might show relatively lower accumulation of FDG than that with scantystroma. We estimated the amount of tumor stroma with FDG-PET (STRpet), and evaluated prognosis ofpatients using STRpet after surgery of pancreatic cancer.MethodsSixteen pre-surgery patients with either proven or suspected primary pancreatic cancer underwent FDG-PET/CT. The pathologically confirmation found out 13 malignancy in all cases. The STRpet in tumor wasevaluated for the 13 cases with the following equation:STRpet = [Mean value of spherical VOI of 10mm in radius with SUVmax in the center of it] / [SUVmax]The tumor with abundant stroma might be low STRpet, because the tumor cell accumulates FDG avidly butstroma does not so much. According to pathological findings, the stroma of tumors (STRpatho) werequantitatively classified in the following 3 types (Scirrhous type: abundant stroma, Intermediate type: a typeintermediate between the scirrhous type and the medullary type, and Medullary type: scanty stroma).The STRpet were statistically compared with STRpatho using the Mann-Whitney\u27s U test. The 1-year disease-free survival (DFS) and overall survival (OS) for STRPEt and STRpatho were calculated using Kaplan-Meiermethod.ResultsThere is no patient with Medullary type in our cases. Statistically-significant difference was observed inSTRpet between Scirrhous type and Intermediate type (p<0.04). Scirrhous type has a lower STRpet thanIntermediate type. The patients with STRpet<0.7 or scirrhous type had markedly lower 1-year DFS rate thanthose with STRpet^O.7 or intermediate type (0% vs. 50% p<0.03, 0% vs. 57% p<0.01). The patients withSTRpet<0.7 or scirrhous type had markedly lower OS rate than those with STRpet^0.7 or intermediate type(0% vs. 50% p<0.05, 0% vs. 57% p