What type of local consolidation therapy, if any, would you offer to a patient with thymoma and pleural metastasis with complete metabolic response after chemotherapy?

A lot of caveats depend on patient age/performance status/comorbidities, the path and extent of initial disease.

Thymoma (depending on path), even with pleural disease, can be quite indolent, and in most cases, you aren't losing much by observing off therapy or on maintenance systemic therapy. Retro...

I would go for a second chance at cure and ablate what might be only a solitary drop met. We have cured patients like this before who have had no further relapse 5 years later.