How would you approach patient with known Lynch Syndrome who developed a gall bladder cancer which on pathologic testing of the tumor by PCR and immunohistochemistry is pMMR and MSS?

Assuming advanced/metastatic disease, for MSS disease, I would use frontline chemoimmuno therapy with cis+gem+durva/pembro. In this case, response to immunotherapy alone may not be comparable to MSI-high disease thus, hesitant to use pembro alone.