For a patient with metastatic gastric adenocarcinoma with CT showing NED after 4 months of FOLFOX + pembrolizumab + trastuzumab, would you consider resection of the primary and/or a chemo break?

This question is about a patient with gastric cancer who has a complete response to therapy with chemotherapy, trastuzumab, and checkpoint inhibitor blockade. The patient had a radiographic CR after 4 months of therapy. How to proceed from here is an interesting question, and would be influenced by specifics of the clinical situation which are not given here. For the purposes of this answer, I will assume that the cancer is not mismatch-repair deficient.

In gastric cancers with HER-2 overexpression (by IHC or FISH), I have observed (and discussed with others) exceptional responses to trastuzumab-containing chemotherapy. In these cases, I have tried to continue systemic chemotherapy (often with capecitabine and trastuzumab) for a year or lon...

I absolutely agree with @Dr. First Last about the duration of systemic therapy (6-12 months at a minimum) before considering surgical management. Most of the surgeons I work with wouldn't even think about operating with curative intent before the 12 month mark.

I also think that the nature of the metastatic disease matters a lot. Although I agree that there are no good data to drive decision making, resection of limited hepatic or pulmonary metastases are going to have better outcomes than peritoneal metastases. The best data I'm aware of in this setting is the AIO-FLOT3 study which had 3 parallel arms, one of which was potentially resectable metastatic disease (the other arms were localized, resectable, and diffuse metastatic). Although on...