Oligo-like liver metastasis: A novel prognostic indicator to improve survival in pancreatic cancer

Purpose: Whether surgical intervention for patients with oligometastatic recurrence can improve their post-recurrent prognosis is unclear. In this study, we introduce a novel concept of oligometastasis in post-surgical pancreatic ductal adenocarcinoma (PDAC) patients with hepatic recurrence, which we call "oligo-like liver metastasis (OLLM)." Patients with OLLM have better post-recurrence prognosis and could therefore be eligible for surgical intervention.Methods: A total of 121 PDAC patients who underwent radical resection, and who had an initial and single-organ metastasis to the liver, were analyzed. Independent prognostic factors for overall survival after recurrence (OSAR) were examined, and patients with all of these factors were defined as OLLM. The clinicopathological features and post-recurrent prognosis of OLLM patients were evaluated. In addition, a detailed analysis using the oligo-score, which was based on the prognostic factors, was performed.Results: The prognostic analysis revealed that short recurrence-free interval (RFI) (<6 months), short stable disease interval (SDI) (<= 3 months), and four or more recurrent tumors were independent poor prognostic factors. OLLM patients were defined as those with all three conditions: long RFI (>= 6 months), long SDI (>3 months), and three or less recurrent tumors. OLLM patients had a significantly better prognosis for OSAR than non-OLLM patients (HR = 0.272, p < 0.001). Further analysis demonstrated that the OSAR of patients could be stratified using the oligo-score, which was calculated based on the prognostic factors.Conclusion: We recommend that OLLM should be used to predict which patients are most likely to experience better post-recurrent prognosis after surgery with curative intent.