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

Overall Response Rate (ORR)

The primary endpoint is Overall Response Rate (ORR) of chemotherapy, defined as the percentage of patients experiencing partial response (PR) or complete response (CR), according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, after starting the treatment with FTD/TPI plus Bevacizumab.

Progression free survival (PFS)

Measured as the time from the start of the treatment with FTD/TPI plus Bevacizumab to the date of first progression, or the date of death from any cause, or the date of the last restaging in non-progressed patients

Safety evaluation

All adverse events will be recorded during the observation period (i.e. from the day of the first DC vaccine dose administered in the induction phase up to 30 days after the last dose of chemotherapy), will be reported and graded according to NCI CTCAE 5.0.

Overall Survival (OS)

Measured from the start of the induction treatment until the date of death from any cause or the last date on which it was known that the patient was alive.

In vivo immunomonitoring through DTH test:

In vivo immunomonitoring through DTH test: DTH testing will be performed in all patients on day 0 (pre-treatment DTH), after the induction phase (post-combo immuno treatment DTH), after the maintenance phase, at the end of treatment and at disease progression. The diameter of induration/erythema observed after 24 hours is recorded according to the following scale: 0-5 mm grade 1, 6-10 mm grade 2, 11-20 mm grade 3, and \> 21 mm grade 4. As DTH reactivity to lower concentrations of the antigen(s) is strictly related to more intense antigen specific immune responses, score results will be normalized against the concentration itself and transformed into a 0-80 scale for analysis purposes. Best results obtained for each patient at any of the posttreatment DTHs, either for tumor homogenate or keyhole limpet hemocyanin (KLH), will be taken into account for data analysis (best normalized score).