Heterogeneous growth rates of pancreatic adenocarcinoma by retrospective analysis of CT imaging data.

Abstract

248 Background: Pancreatic ductal adenocarcinoma (PDAC) remains the fourth leading cause of cancer death in the United States. Despite its high mortality, there is no effective screening method or frequency. The purpose of this study is to retrospectively evaluate prediagnostic CT images in order to identify growth rate and determine a potential surveillance frequency for at risk patients. Methods: 188 PDAC patients were seen at Banner MD Anderson Cancer Center (BMDACC) from 1/1/2012 to 12/31/2015. 24 patients met the final inclusion and exclusion criteria. Tumor area on CT imaging was then evaluated for rate of change prior to diagnosis. Both absolute and relative areas were plotted against time prior to diagnosis at 3, 6, 9, 12, 24, 36, 48, 60, and 72 months. Results: With two exceptions, no evidence of malignancy was identifiable at two or more years prior to diagnosis. Growth rates per year varied significantly. Absolute area change ranged from 1.7 cm2/yr to 139.22 cm2/yr; relative area change ranged from 1.17 to 7.15. Assuming a spherical mass, these relative changes correspond to relative volume change (ratio) per year of 1.27 and 19.13; the equivalent linear tumor doubling times are 3.7 years and 20 days respectively. Student’s T-test yielded no significant difference for relative growth, absolute growth, PFS, or OS between male and female patients. Conclusions: The heterogeneity in growth rate has significant implications for potential screening of PDAC. Screening interval greater than 1 year is feasible with other slow growing tumors. However, annual screening is not feasible for rapidly growing PDAC. Based on our findings, screening may need to be as frequent as 3-month intervals which would incur significant economic cost. Further correlation of prediagnostic growth rate with molecular changes may be necessary to discover the driver of this heterogeneous growth pattern.