Tumor Downsizing Following Neoadjuvant Therapy For Borderline-Resectable Pancreatic Adenocarcinoma

690 Background: Downstaging of pancreatic adenocarcinoma in patients presenting with nonmetastatic, unresectable disease has proven to be associated with improved clinical outcomes. Efforts at rescuing these patients to become surgical candidates are commonly attempted with a combination of systemic and radiation strategies. In this study, we aimed to determine tumor downsizing in patients that underwent neoadjuvant systemic therapy followed by a curative-intended surgical resection. Methods: A retrospective review of consecutive patients that underwent surgical resection for pancreatic adenocarcinoma following a course of neoadjuvant therapy was performed. Basic demographics, endoscopic ultrasound (EUS) findings, chemotherapy regimens and duration, rates of radiotherapy, type of surgical procedure and pathologic results were recorded. Tumor response to neoadjuvant therapy was established by correlating EUS- to pathologic tumor dimensions. Analysis of the data was done using Mann-Whitney U test, Pearson correlation and Chi-square when indicated. Results: A total of 97 patients were analyzed; 40 underwent neoadjuvant chemotherapy (13 patients also received concurrent radiation therapy). In those 57 patients that were resected upfront, EUS tended to underestimate tumor sizes significantly compared to pathologic dimensions, with an average difference between dimensions of 0.66 cm (p = 0.0004). Within the group treated with neoadjuvant chemotherapy, 90% of patients had downsizing at an average of 8% of tumor size. There were no differences in rates of tumor downsizing between FOLFIRINOX or Gemcitabine/Nac-paclitaxel treated patients. In addition, there were no correlations in margin status (R0) based on chemotherapy used, with both regimens achieving a similar rate of R0 resections (mean 61%). The type of chemotherapy regimen used did not affect the ratio of positive lymph nodes harvested. Conclusions: In patients that present with borderline resectable pancreatic adenocarcinoma, a course of neoadjuvant therapy results in tumor downsizing in a significant number allowing for margin negative resections. These results were seen regardless of the chemotherapeutic regimens utilized.