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e14032 Background: Polymorphisms in MGMT gene have been implicated in temozolomide (TMZ)-induced hematological toxicity in patients with adult diffuse gliomas. We aimed to investigate the association of three single nucleotide polymorphisms (SNPs) in the MGMT gene viz. L84F, I143V/K178R with severe hematological toxicity in patients of adult diffuse glioma treated with TMZ at an academic neuro-oncology unit of a tertiary-care comprehensive cancer centre from India. Methods: Thirty-three patients of adult diffuse glioma treated with multi-modality adjuvant therapy including TMZ who developed CTCAE V5.0 grade 2-4 hematological toxicity were included after written informed consent. Genomic DNA was extracted from peripheral blood mononuclear cells for SNP analysis. Correlation of MGMT SNP with patient demographics and hematological toxicity was assessed using the Chi-square and Fisher’s exact test. Results: Twenty-four patients (72.7%) developed grade 3-4 hematological toxicity with TMZ with a distinct female predilection. The variant T allele of L84F was expressed in 28.7% of the total 66 analyzed alleles which was markedly higher than previously reported in the general population of South Asian ancestry. The variant G allele of I43V/K178R was expressed in 9.3% (6/64) of 64 analyzed alleles. Persistent myelosuppression lasting beyond 2 months after cessation of TMZ correlated with I143V/K178R hetero/homozygous compared to wild type allele (p = 0.03). However, no significant correlation could be seen between any of the tested MGMT SNPs and grade of hematological toxicity. Conclusions: There is a higher prevalence of the L84F polymorphism in Indian patients with severe hematological toxicity than previously reported in the literature. The variant G allele of I143V/K178R is associated with prolonged and persistent myelosuppression induced by TMZ. A larger case-control is being planned to further elucidate the causal relationship between MGMT gene polymorphisms and TMZ-induced severe hematological toxicity.