Natural History of Stage IV Pancreatic Cancer. Identifying Survival Benchmarks for Curative-intent Resection in Patients With Synchronous Liver-only Metastases.

Objective: To evaluate long-term oncologic outcomes of patients with stage IV pancreatic ductal adenocarcinoma and to identify survival benchmarks for comparison when considering resection in these patients.

Background: Highly selected cohorts of patients with liver-oligometastatic pancreas cancer have reported prolonged survival after resection. The long-term impact of surgery in this setting remains undefined because of a lack of appropriate control groups.

Methods: We identified patients with clinical stage IV pancreatic ductal adenocarcinoma with synchronous liver metastases within our cancer registry. We estimated overall survival (OS) among various patient subgroups using the Kaplan-Meier method. To mitigate immortal time bias, we analyzed long-term outcomes of patients who survived beyond 12 months (landmark time) from diagnosis.

Results: We identified 241 patients. Median OS was 7 months (95% CI, 5-9), both overall and for patients with liver-only metastasis (n=144). Ninety patients (38% of liver only; 40% of whole cohort) survived at least 12 months; those who received chemotherapy in this subgroup had a median OS of 26 months (95% CI, 17-39). Of these patients, those with resectable or borderline resectable primary tumors and resectable liver-only metastasis (n=9, 4%) had a median OS of 39 months (95% CI, 13-NR).

Conclusions: The 4% of our cohort that were potentially eligible for surgery experienced a prolonged survival compared with all-comers with stage IV disease. Oncologic outcomes of patients undergoing resection of metastatic pancreas cancer should be assessed in the context of the expected survival of patients potentially eligible for surgery and not relative to all patients with stage IV disease.