How would you manage an enlarging brain metastasis that has progressed in size three months after radiosurgery?

Before making a decision, I would want to know the tumor histology, SRS dose delivered, and whether the current site of progression is truly within the prior radiation field (using new MRI fused to the SRS plan in treatment planning software).

If the lesion is within the high-dose region and the patient is asymptomatic, the most reasonable next step is close follow-up with repeat brain MRI in 6-8 weeks, ideally with perfusion sequence, to help clarify progression versus early post-treatment RT e...

This is an uncommon situation, and to adequately answer the question, it would be nice to know the histology, the dose of SRS used, the PTV margin, and whether immune checkpoint inhibitors were used concurrently. For example, if the histology was NSCLCa and a dose of 24 Gy was used and the PTV was 2 mm, could this apparent increase in size be radiation necrosis? Whereas, if a lower dose of 18 Gy was used and the histology was RCC or melanoma, it could very well be that the tumor survived and kep...

This review would suggest that 1/3rd transiently enlarge after SRS: Patel et al., PMID 21920854.

Consider also the "Bergen" criteria: Skeie et al., PMID 32642686.

No response with sustained, continued true progression, I think, is quite rare.

I never have, and likely never would, retreat a metastasis that went from 3 mm pre-SRS to 8 mm on first follow-up. Surgery, if very problematic. Otherwise, continue to follow and use advanced imaging and evolution to try and determine treatment effect vs true ...