Clinical efficacy of adjuvant surgery following systemic treatments in patients with initially unresectable pancreatic cancer: Results of a project study for pancreatic surgery by the Japanese Society of Hepato-Biliary-Pancreatic Surgery.
255 Background: Medical oncologists or pancreatic surgeons have identified candidates for surgical resection in patients with initially unresectable pancreatic cancer who favorably responded to multimodal treatment. Additional surgical resection during multimodal treatment, is called “adjuvant surgery”. A multicenter survey was conducted to explore the clinical efficacy of adjuvant surgery for initially unresectable pancreatic cancer with a long-term favorable response to systemic treatments. Methods: Clinical data, including the primary endpoint of overall survival were retrospectively compared between 58 initially unresectable pancreatic cancer patients that underwent adjuvant surgery with a favorable response to non-surgical cancer treatments over 6 months after the initial treatment (adjuvant surgery group) and 101 patients who did not undergo adjuvant surgery (control group). Results: The median observation periods were 51 months (20-122) in the control group, and 54 months (26-125) in the adjuvant surgery group, respectively. The actuarial survival rate at 1, 3, and 5 years after initial treatment in adjuvant surgery group (95, 53, and 34%) was significantly better than that in control group (88, 18, and 10%, p<0.0001). The propensity score analysis to provide adjustment of significant differences in the clinical backgrounds between the two groups revealed that adjuvant surgery was a significant independent prognostic variable with an adjusted hazard ratio (95% confidential interval) of 0.569 (0.36-0.89). Subgroup analysis according to the time from initial treatment to surgical resection showed a significant favorable difference in the overall survival in patients who underwent adjuvant surgery over 240 days after the initial treatment. Conclusions: The adjuvant surgery can occupy an important position in the multimodal therapy for patients with initially unresectable pancreatic cancer. The overall survival rate from the initial treatment is extremely high, especially in patients who received systemic treatments for more than 240 days.