I would argue for Whole Brain Irradiation also even though MRI does not show any evidence of disease. Intracranial metastasis (solitary mets) are best treated with Surgical Resection followed by WBRT. See the latest update on Pubmed Central (luckily they have contributed the article for open access):
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808516/?tool=pubmed
To quote for Level I evidence:
Level 1 Surgical resection followed by WBRT represents a superior treatment modality, in terms of improving tumor control at the original site of the metastasis and in the brain overall, when compared to surgical resection alone.
I have included this link from Pubmed where in they have mentioned the treatment for primary intracranial germ cell tumors
http://www.ncbi.nlm.nih.gov/pubmed/14585229 and to quote from the abstract:
Patients with nongerminomas respond best to chemotherapy combined with radiation, although the response and cure rates are lower compared to germinomas.
Finally the big issue of CSI. This is not a common situation and hence there can be no "guidelines" for such a scenario. Hence, a Pubmed search revealed a retrospective series which is uploaded here:
http://www.scribd.com/full/40731198?access_key=key-87qlux06wroxhhwtu0i
Please feel free to download it. It says that CSI improved the outcomes. If there were a focal lesion, would it be appropriate to give CSI to a dose of say 36 Gy, followed by boost to the local lesion ?
Thats my opinion though.
