Results
Within our study population, 46 out of 242 patients were tested for MTHFR SNPs with 33 resulting positive for a known MTHFR polymorphism. Patients with MTHFR genotypes including those who were homozygous 677TT and compound heterozygous 677CT/1298AC demonstrated significantly decreased tolerance to oral MTX as demonstrated by decreased maximum tolerated MTX dosing relative to control and the 677TT genotype also demonstrated reduced tolerance to IV MTX (Capizzi MTX). Clinically significant MTHFR genotypes were likely to be detected in the presence of myelosuppression, but no other known MTX adverse effects demonstrated predictive ability. Lastly, no genotype was associated with increased risk of developing MTX leukoencephalopathy or thrombosis with any SNP.