BACKGROUND: To compare survival and hematological toxicity rates between two 
postoperative therapy regimens in patients with primary glioblastoma (GBM), 
namely temozolomide (TMZ) concomitant to radiation, followed by adjuvant TMZ, 
versus adjuvant TMZ after radiation only.
PATIENTS AND METHODS: A total of 191 patients with primary GBM were 
postoperatively treated with either radiation and concomitant TMZ, followed by 
adjuvant TMZ (Stupp protocol) (n = 154), or radiation followed by adjuvant TMZ 
(n = 37). The incidence of hematological adverse effects (AE) was recorded for 
all patients. From both treatment groups, 26 patients were matched according to 
age, Karnofsky performance scale (KPS) score, and 
O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation.
RESULTS: Hematological AEs were mild in both unmatched groups, but were 
significantly more frequent in the concomitant plus adjuvant TMZ group (p < 
0.001). Matched-pair analysis confirmed significantly more frequent 
hematological AEs in the concomitant and adjuvant group compared to the 
sequential (adjuvant) TMZ group (p = 0,012). Patients treated with concomitant 
plus adjuvant TMZ showed significantly longer progression-free survival (PFS) 
(10.6 versus 6.6 months; p = 0.014), but no prolonged overall survival (OS) 
(16.9 vs. 15.6 months; p = 0.717) compared to patients who received the 
sequential treatment regimen.
CONCLUSION: In this retrospective study, the OS in patients with primary GBM 
treated with sequential TMZ following radiation appeared to be similar to that 
in patients treated with concomitant plus adjuvant TMZ. Given the significantly 
higher risk of hematological AE for concomitant treatment, the role of 
concomitant plus adjuvant TMZ use compared to sequential administration of TMZ, 
especially for patients with MGMT-unmethylated tumors, should be further 
evaluated.