Is there a difference in the incidence of serious immune-related adverse events with the lenvatinib + pembrolizumab combination vs pembrolizumab alone in endometrial cancer?   

Yes, high risk of both hypertension and diarrhea.  The diarrhea can be very difficult to manage.  The lenvatinib definitely adds a level of complexity to the management of pembro side effects.  This requires dose reductions and interruptions, maybe even hospitalization for dehydration...

Their dose not appear to be a significant difference in immune mediated AEs with the combination regimen.  There are some AEs that can result from either drug, perhaps best exemplified by the diarrhea, requiring close and careful monitoring.  

Combination of pembrolizumab and lenvatinib has been shown to be superior to sunitinib in advanced renal cancer (Motzer et al., PMID 33616314), and superior to chemotherapy in advanced (pMMR/dMMR) endometrial cancer (Makker et al., PMID 35045221). However, this combination has not been shown to be s...