For patients with the proneural subtype of glioblastoma, there was a trend for improved PFS HR with low (cut off Q1) versus high plasma YKL-40 levels (> Q1), although CIs overlapped: PFS HR 0.41 (95% CI: 0.13–1.28) versus 0.80 (95% CI: 0.45–1.40). This evidence concerns the gene CHI3L1 and glioblastoma.