This is a small descriptive study assessing the GB microenvironment in a paired tissue cohort by immunofluorescence and histology (n=11, early recurrence; n=12, late recurrence). Classical markers are used to characterize cells within the TME. At early recurrence, the authors describe a particularly reactive tumor region encompassing fibrosis, chronic inflammation, TAMs and tumor cells and speculate that this might result in a time-dependent response to immunotherapy. The study has clear limitations as stated by the authors themselves.

Major points:

• MGMT promotor status should be displayed as this represents a strong confounder and unmethylated MGMT-P is associated with early recurrence
• Time from last dose of RT should be displayed, correlative analyses (time post RT) to TME phenotypes could be interesting to visualize
• The terminology M1/M2 is referring to in vitro phenotypes and the authors correctly state that multiple distinct TAM phenotypes likely co-exist, hence, I would suggest to rename into M1-like / M2-like