Background: In gliomatosis cerebri (GC), defined as a diffuse neoplastic glial cell infiltration of the brain, upfront chemotherapy is often proposed as an alternative to radiotherapy. GC invades both white matter and gray matter in varying proportions, as reflected by the gray matter index (GMI), i.e., the estimated percentage of gray matter involvement.
Methods: The GMI was estimated in 71 patients with GC (42 men and 29 women; median age, 47 years) treated with upfront chemotherapy (7 PCV, 64 temozolomide).
Results: Median GMI was 30%. Patients were separated into 2 groups according to this median GMI. Compared to the 33 patients with GMI >30% (group B), the 38 patients from group A (defined as GMI <or=30%) had better performance status (p = 0.03), higher response rate to chemotherapy (30/38 vs only 5/33; p < 0.0001), longer progression-free survival (21.2 vs 11.7 months, p = 0.005), and longer overall survival (56.1 vs 26.4 months; p = 0.003). There was no significant correlation with histologic subtype (oligodendroglial vs astrocytic or mixed GC), grading, tumor localization (particularly basal nuclei involvement), or laterality. The deletion of chromosomes 1p and 19q tended to be more frequent in group A (8/17 [47%] vs 1/9 [11%] in group B [p = 0.057]).
Conclusion: These data suggest that gray matter index is a prognostic and predictive marker in gliomatosis cerebri that may in part depend on the 1p/19q status.