Sequential Immunochemotherapy Treatment with Pembrolizumab Plus Dendritic Cell (DC) Vaccine Followed by Trifluridine/Tipiracil Plus Bevacizumab in Refractory Mismatch-repair-proficient (pMMR) or Microsatellite-stable (MSS) Metastatic Colorectal Cancer

This trial is testing a sequence of treatments — immunotherapy (pembrolizumab) plus a personalized dendritic cell vaccine, followed by trifluridine/tipiracil and bevacizumab — for people with metastatic colorectal cancer that has a specific genetic profile (pMMR or MSS) and has not responded to standard chemotherapy. **You may be eligible if...** - You are 18 or older - You have confirmed metastatic colorectal cancer that is pMMR or MSS (a genetic feature meaning it does not respond to standard immunotherapy alone) - You have had 1–2 prior chemotherapy regimens including fluoropyrimidines, irinotecan, oxaliplatin, anti-VEGF, and/or anti-EGFR drugs - You have measurable disease on CT or MRI - Your blood counts and organ function are adequate - A tumor sample was previously collected and sent to the lab for vaccine manufacturing - You are not pregnant or breastfeeding **You may NOT be eligible if...** - You have not completed the required prior chemotherapy regimens - Your tumor sample is not available or does not meet lab acceptance criteria - You have unresolved serious side effects from prior treatments or surgery - You are currently pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.