What is your recommended dose and treatment volume for multifocal glioblastoma involving the bilateral cerebral hemispheres?

Median survival of multifocal/multicentric GBM is only about 5-10 months across series, and a recent study reported 2-year survival only 4% (PMID:22920963). Optimal radiation dose will depend on performance status, neurologic status, comorbidities, age, and social situation. Reasonable doses are:

- 0 Gy. Best supportive care / hospice

- 25 Gy = 5 Gy x 5 to enhancing disease +/- FLAIR with margin

- 34 Gy = 3.4 Gy x 10 to enhancing disease +/- FLAIR with margin

- 40.05 Gy = 2.67 Gy x 15 to enhancing disease +/- FLAIR with margin

Since the goal is realistically palliation, not cure, I generally favor partial brain treatment. As far as I am aware there is no evidence that whole brain treatment improves outcomes, and quality of life tends to be bett...