Background: GBM is the most common and aggressive primary brain tumor. The neutrophil to lymphocyte ratio (NLR) gives a measure of systemic inflammatory response and lymphopenia, both of which are poor prognostic factors in many malignancies. No published study has assessed the prognostic impact of NLR in GBM. Methods: Patients treated for GBM at our regional referral centre with assessable complete blood count at first presentation (prior to corticosteroid therapy or surgery) were identified. Medical notes were reviewed to extract demographic and treatment data. Survival curves were estimated via Kaplan-Meier method and compared via log-rank method. Multivariate analysis was performed via Cox proportional hazards regression modelling. Results: A total of 86 patients were identified, of which 65(76%) were male. Median age at diagnosis was 58 years (range: 18–76). At the time of analysis all patients still alive had ≥ 2 years follow-up. Median overall survival (OS) was 9.3 months (range: 1-82). 57% completed the standard adjuvant Stupp protocol and 43% discontinued early due to disease progression or treatment toxicity. Median OS was 11.2 months in patients with NLR<4 and 7.5 months in patients with NLR>4 (HR 0.59, p=.04). Other significant prognostic factors based on univariate analysis were consistent with published data (Table). After correcting for known prognostic factors NLR remained a significant predictor of survival (Table). Conclusions: Recent advances in immunotherapy have highlighted the importance of the immune system in the treatment and prognosis of cancer patients. Many GBM patients are on corticosteroids for a significant proportion of their disease course which may abrogate the effects of host immunity on outcome. Nevertheless, we have shown that NLR at diagnosis is an independent predictor of survival in GBM patients. Investigation of therapies which harness the immune response are warranted in this disease.

	Univariate		Multivariate
	Hazard ratio	p value	p value
NLR (<4 vs >4)	0.59	0.01	0.01
Age (<60 vs ≥60)	0.47	<0.01	0.01
Surgery (debulking vs biopsy)	0.60	0.01	0.01
Stupp protocol (complete vs incomplete)	0.21	<0.01	<0.01