What is your cutoff for the maximum number and size of brain metastases that you will treat with SRS?

Sadly, the level 1 evidence needed to truly delineate the greatest benefits from SRS will probably never be realized beyound what we already know: SRS shows an OS benefit to pateint with 1 intracranial met and a CNS-DFS benefit to 2-3 mets. Beyond that, it's better in terms of preservation of neurocogntive function at a few months to 12 months of follow up. In those patients (most we see in reality) with active extra-cranial disease, survival is typically driven by an uncontrolled primary or liver/visceral mets and the SRS or whatever form of beam you choose holds the brain in check. I wonder what the real point of doing follow up brain studies is good for; is there any data suggesting any survival benefit to re-treating the brain with beam...

Everything that can be counted does not necessarily count; everything that counts cannot necessarily be counted. - Albert Einstein

We dont count the mets as long as patient has a high KPS and has systemic options.

1. Rivers C, Tranquilli M, Prasad S, Winograd E, Plunkett R, J, Fenstermaker R, A, Fabiano A, J, Podgorsak M, B, Prasad D, Impact of the Number of Metastatic Tumors Treated by Stereotactic Radiosurgery on the Dose to Normal Brain: Implications for Brain Protection. Stereotact Funct Neurosurg 2017;95:352-358
2. Rivers C, Prasad S, Bass M, Tranquilli M, Malhotra H, Plunkett RJ, Fenstermaker RA and Prasad D. Brain and hippocampal doses in patients with repeated stereotactic radiosurgery for brain metastasis. Radiat Oncol 2017 6: 49. doi...

It depends on whether the patient has newly diagnosed brain metastases or whether he/she has already had whole brain radiation therapy (WBRT).

If prior WBRT then I will treat growing lesions up to 10 but since I am treating usually on the brainlab machine with relocatable mask, I usually divide into 2-3 consecutive days. We have a gammaknife in our hospital so I will usually tell a patient that treatment might be quicker and done in one session on the gammaknife. But most patients would still prefer to stay for brainlab so they don't have the frame fixation. Or maybe it is that they don't want to change physicians at that point? I think that it would be great to do a patient decision analysis comparing these 2 treatments- I am thinking seri...

As in much of retrospective observational studies, we never know the process of selection. SRS is incredibly benign. As we will now see nationally with President Carter, if I had what he had I'd want SRS, not WBRT. The indictment of WBRT is anecdotal. How do you rule out underlying micrometastasis? Enthusiasm for multiple lesions in long-surviving patients is understadable, but size, age, performance status, extent and activity of systemic disease are selection factors, and survival is dominated by those, and brain control and breain progression are also factors. Getting MR every 2 weeks looking for new targets seems extreme...

http://www.ncbi.nlm.nih.gov/pubmed/21121790

I think most radio surgeons would say about 10 metastases would be maximum especially if new presentation with no WBRT. Some people would use total metastases volume constraints (20cc in most european studies, 15mm in the Yamamoto data)

http://www.ncbi.nlm.nih.gov/pubmed/24621620

Although the same group have recently published data in more than 10 mets

http://www.ncbi.nlm.nih.gov/pubmed/25434933

i would say up to 10 and/or up to 20cc would seem reasonable starting points to consider applying as cut offs..