Do patients with metastatic pancreatic adenocarcinoma to the lung have improved survival?

INTRODUCTION: Pancreatic ductal adenocarcinoma (PDAC) is a genetically heterogeneous disease often diagnosed with synchronous metastatic disease involving the liver. Tumors with extra-abdominal spread that bypass the liver are thought to represent a unique molecular subgroup and those with isolated pulmonary metastatic disease are thought to have a more favorable clinical phenotype.

METHOD: We conducted a retrospective review of patients with pathologically confirmed PDAC treated between the years 2007 and 2020 at a Scripps Health hospital. The final study sample (N = 205) included patients with isolated pulmonary metastasis (IL), isolated liver metastasis or synchronous liver and lung metastasis (LL), or metastasis to any site other than the liver or lung (NLL). Primary endpoint was overall survival (OS). Progression-free survival (PFS) and recurrence-free survival (RFS) were analyzed as secondary endpoints. Each survival outcome was analyzed using Cox proportional hazards tests.

RESULTS: No statistically significant differences were seen between the three groups in OS, PFS, or RFS. Median OS for the IL group was 561 days, 341 days for the LL group, and 441 days for the NLL group. Median RFS was 748 days for the IL group, 574 days for the LL group, and 545 days for the NLL group. Median PFS was 307 for the IL group, 236 for the LL group, and 265 for the NLL group. When comparing only the IL and LL groups, a statistically significant difference in OS was seen favoring the IL group (HR1.59 LL vs IL [ref], CI 1.04-2.41, p = 0.031) CONCLUSION: Though statistically significant differences in survival outcomes were not seen in our population, there was a trend toward improved survival for patients with isolated lung metastases. When comparing only the IL to LL group, statistically significant overall survival favoring the IL group was seen. These findings highlight a potential prognostic indicator of metastatic PDAC.