Pembrolizumab and Autologous Dendritic Cells for the Treatment of Refractory Colorectal Cancer (CRC)

PRIMARY OBJECTIVE: I. To determine the clinical efficacy of pembrolizumab in combination with intratumorally injected autologous dendritic cells (DCs) in refractory metastatic colorectal cancer (CRC). SECONDARY OBJECTIVES: I. To evaluate the safety profile of pembrolizumab in combination with intratumorally injected autologous dendritic cells (DCs) in CRC patients. II. To assess progression-free survival (PFS) in CRC patients receiving pembrolizumab in combination with intratumorally injected autologous dendritic cells (DCs). III. To assess overall survival (OS) in CRC patients receiving pembrolizumab in combination with intratumorally injected autologous dendritic cells (DCs). IV. To assess objective response as determined by Immune-related Response Evaluation Criteria in Solid Tumors (iRECIST). EXPLORATORY OBJECTIVES: I. To conduct correlative science studies including: Ia. Comparison of the metastatic tissue specimen with regard to total numbers of infiltrating T cells, their CD4/CD8 ratios, frequencies of Tregs, and their expression of chemokine receptors. Ib. Evaluate the local expression of T eff-attracting chemokines and T reg-favoring chemokines using immunofluorescence (IF) and reverse transcription-polymerase chain reaction (RT-PCR). OUTLINE: Patients receive pembrolizumab intravenously (IV) on days 8, 29, 50, and 71, and autologous dendritic cells intratumorally on days 1 and 8 in the absence of disease progression or unacceptable toxicity. Patients may also receive an autologous dendritic cells intratumorally on day 50. After completion study treatment, patients are followed up at 30 and 90 days, and then every 3 months for 12 months.