Preliminary safety data from a randomized multicenter phase Ib/II study of neoadjuvant chemoradiation therapy (CRT) alone or in combination with pembrolizumab in patients with resectable or borderline resectable pancreatic cancer.

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4125 Background: Pancreatic cancer (PC) is a challenging target for immunotherapy.Tumor-infiltrating lymphocytes (TILs) do not reach the PC cells in significant numbers due to the presence of stroma and a suppressive microenvironment. Neoadjuvant chemoradiation (CRT) can increase the presence of TILs in the PC microenvironment. We hypothesized that combination of CRT and pembrolizumab can lead to further increase in TILs and their activation. Methods: Patients with resectable or borderline resectable PC have been randomized 2:1 to the investigational treatment (Arm A) to receive pembrolizumab 200mg IV every 3 weeks on days 1, 22, and 43 during concurrent CRT with capecitabine (825 mg/m2 orally twice daily, Monday-Friday, on days of radiation only) and radiation (50.4 Gy in 28 fractions over 28 days) or Arm B to receive only concurrent CRT with capecitabine. Restaging CT scan or MRI is performed at 4-6 weeks after completion of neoadjuvant treatment, and patients with resectable disease will undergo surgical resection. Here we report the preliminary safety data based on 22 enrolled patients. Results: As of February 3-2017,22 patients have been enrolled (14 Arm A and 8 Arm B). 50% of the patients had resectable disease (7 arm A; 4 arm B) and the other 50% had borderline resectable disease (7 Arm A; 4 arm B). Post-neoadjuvant therapy, 6 patients had unresectable disease (3 on each arm), and 14 patients underwent surgery (10 arm A and 4 arm B). There were 7 grade 3 treatment-related toxicities in Arm A (5 patients): 2 grade 3 diarrhea attributed to CRT; 4 grade 3 lymphopenias attributed to pembrolizumab, CRT or the combination; and one patient had elevated alkaline phosphatase probably related to the combination that met the definition of DLT and resolved after holding the treatment and receiving steroids. There was only one grade 3 toxicity on Arm B: lymphopenia attributed to CRT. No grade 4 toxicities have been reported on either arm. There were no major surgical complications reported within 30 days post-surgery. Conclusions: The combination of CRT and pembrolizuamb is safe based on the presented data. Clinical trial information: NCT02305186.