The economic impact of short-term imaging with metastatic pancreatic ductal adenocarcinoma.

Abstract

643 Background: Although modern cancer treatment has significantly improved overall survival, this comes with a high financial cost. Based on an NIH report on Financial Burden of Cancer Care, treating pancreatic adenocarcinoma (PDAC) costs $108K, $18K, and $125K for initial treatment, during follow-up, and in last year of life, respectively. During the course of treatment, patients will visit the hospital for acute symptoms for which cross-sectional imaging is obtained within 45 days of subsequent scheduled follow-up imaging. This presents an opportunity for cost saving if data could be collected to identify an algorithm to avoid unnecessary duplication of imaging in a short interval. The purpose of this pilot study is to evaluate tumor growth trajectory within this short time span of 45 days to guide future trials to clarify the circumstances for which a subsequent follow up study is necessary. Methods: We retrospectively identified patients from our tumor registry from 2016 to 2019 who were diagnosed with metastatic PDAC (mPDAC). Subjects were included for analysis if they met the following criteria: 1) diagnosed with mPDAC; 2) had at least 2 CT abdomen/pelvis (CTAP) within 45 days of each other with one of the studies being obtained in the emergency department; and 3) had at least 1-3 measurable lesions as defined by RECIST 1.1 criteria. Tumor dimension was measured on axial images with the largest cross-section. For our primary outcome we used paired t-tests to evaluate the difference in mean size of all lesions (primary and metastatic). We also performed sub-group analyses comparing mean size of primary and metastatic lesions separately. An alpha level of 0.05 was used to determine statistical significance. Results: We screened 383 subjects from the tumor registry and identified 28 subjects suitable for our study. 18 subjects were female and 10 were male. We identified 69 target lesions, 23 of which were primary and 46 were metastatic. The mean sum of the largest dimension of target lesions was 2.82 cm on the initial study and 3.23 on the latter study (p<0.001). The mean sum of the largest dimension of the primary lesion was 3.62 cm on the initial study and 3.89 on the latter study (p=0.01). For metastatic lesions, the initial sum was 2.38 cm while the latter was 2.85 (p<0.001). Conclusions: Our finding of increase in tumor size in 45 days for mPDAC suggests that mPDAC is aggressive and can grow even in short time span. This suggests that if progression is identified on a study obtained within 45 days of scheduled follow-up, the follow-up study could be cancelled to avoid added cost to the patient. However, if the earlier study is stable or shows response, the scheduled follow-up may still be necessary to demonstrate continued stability/response.