Background : Reports on conversion surgery (CS) for unresectable locally advanced pancreatic cancer (URLA-PC) have been gradually increasing; however, the optimal duration of down-staging chemotherapy remains undetermined.

Methods : In total, 88 patients diagnosed with URLA-PC between 2008 and 2022 were identified. At our institution, surgical indication for URLA-PC is defined as a patient who has a treatment response of SD or better on RECIST after at least 6 months of chemotherapy. Among patients who underwent CS, the cut-off of optimal duration of chemotherapy was determined by minimum p-value analysis, and its impact on overall survival (OS) was evaluated through multivariable analysis.

Results : Thirty-nine patients achieved CS with median survival time (MST) of 25.8 months, whereas 49 individuals were unable to undergo CS with MST of 13.4 months. Among patients undergoing CS, most frequent regimen was GEM+nab-PTX (n=16, 41%), following by GEM+S-1 (n=11, 28%), mFOLFIRINOX (n=9, 23%), and GEM only (n=3, 8%); R0 resection was achieved in 77% of CS patients (n=30). High proportion of patients experienced recurrence after CS (n=28, 72%). The X-tile software identified a chemotherapy duration ≥ 9 month as the optimal cut-off based on OS. Multivariable analysis revealed chemotherapy duration ≥ 9 months (HR: 2.91, 95%CI 1.19-7.71) and presence of adjuvant chemotherapy (HR: 6.11, 95%CI 2.04-18.3) were independent prognostic factors of patients who underwent CS.

Conclusions : Since high proportion of URLA-PC patients experienced recurrence even after CS, a combination of perioperative chemotherapy is expected to improve the prognosis.