The impact of lung and bone metastases on prognosis in advanced PDAC

494 Background: Pancreatic ductal adenocarcinoma (PDAC) remains a highly fatal disease inherently resistant to cytotoxic treatment. Despite the prevalence of liver and peritoneal metastases, subsets of patients also develop lung and bone metastases highlighting phenotypic heterogeneity. We reviewed the prognostic implications of metastatic sites on survival. Methods: This retrospective cohort study included all patients with PDAC who received surgical or oncological treatment at the University Health Network from September 2012 until December 2016. Clinical and pathological variables were obtained from patient electronic records. Radiological images and pathology reports were reviewed to ascertain sites of metastatic disease. The Kaplan-Meier method for survival and multivariable cox regression analysis identified prognostic factors. Results: 1153 patients were reviewed and 985 were included. 55% were male and the median age at diagnosis was 67 years. 287 (29%) completed curative surgery and 698 (71%) had locally advanced or metastatic disease; the median survival was 22 months and 9 months respectively. Lung and bone metastases were present in 18% (N = 180) and 6% (N = 58) of patients. In multivariable analysis increasing age and stage at diagnosis correlated with inferior survival (p < 0.0001) and the presence of any lung (HR 0.77; 95% CI 0.63-0.94, p = 0.01) or bone metastases (HR 0.74; 95% CI 0.54-1.0, p = 0.05) resulted in improved outcomes. Liver and peritoneal disease were not prognostic. Sex and family history of PDAC did not associate with survival. There was no association between site of metastases and sex however patients with bone metastases were significantly younger at first diagnosis (median age 63yrs, p < 0.01). Conclusions: Patients with advanced PDAC and metastases to lung or bone may represent distinct biological subtypes of PDAC. Molecular profiling of available tissue is ongoing.