Patient Characteristics Associated with Definitive Diagnosis of Metastatic Pancreatic Cancer in Those Initially Diagnosed with Cancer of Unknown Primary.

Cancer of unknown primary (CUP) is the fourth most common cause of cancer mortality in the U.S. Median survival after CUP diagnosis is 3-4 months. As CUP and metastatic pancreatic cancer (PC) are comparable in prevalence and survival, PC diagnosis is a useful endpoint to assess patient characteristics associated with definitive diagnosis in older patients who initially present with CUP. This study used 2010-2015 SEER-Medicare data. Logistic regression models compared patient characteristics who received definitive diagnosis in two subsets: CUP-PC and PC only. Approximately 26% of patients who received a definitive diagnosis of metastatic pancreatic cancer started with an initial diagnosis of CUP (n=17,565). The odds of definitive diagnosis in CUP-PC were lower for those with a comorbidity score of 0 (OR 0.85 [0.79, 0.91]) and epithelial/unspecified histology (OR 0.76 [0.71, 0.82]). The odds of definitive diagnosis in CUP-PC were higher for patients of Other race (OR 1.27 [1.13, 1.43]) compared to White patients. Definitive diagnosis of CUP-PC was favorable in patients in the Other race category with fewer or no comorbidities. Unfavorable characteristics included older patients and those with epithelial/unspecified histology. Future studies will focus on patterns of care and survival in patients with CUP-PC.