Can a second course of SRS be used to treat a brain met that initially responded to SRS and then progressed?

One should use caution in interpreting imaging as a definitive sign of progression, as sometimes radiation necrosis can mimic those findings. if asymptomatic, the patient can be considered for close observation with imaging and if symptomatic, one should consider a surgical option also.

If there is compelling evidence for recurrence, there are a few small case series that demonstrate feasibility of repeat SRS. We recently presented our own series at ASTRO (http://www.redjournal.org/article/S0360-3016(14)01740-4/fulltext) demonstrating a 1y LRFS of 62.4% with 17% risk (4 pts) of gra...

I agree with caution in interpreting the results of PET and MRI spectroscopy. The specificity of PET, MRI, and MR spectroscopy vary from 50-80%. We have had a number of cases in which PET and MR spec were consistent with progressive disease and surgical pathology on the whole lesion showed radionecr...