Although MTHFR C677T polymorphism might act as forecasters for grade 3 or grade 4 neutropenia, diarrhea, and mucositis, this polymorphism was found to increase significantly (P = 0.006) the response of 5-FU.
Therefore, the MTHFR C677T polymorphism could be a predictive factor for leukopenia, neutropenia, nausea, and fatigue toxicities in non-sq NSCLC patients treated with single-agent PEM.
A borderline statistically significant relationship was detected after methotrexate administration, between the C677T genotype (polymorphisms) and leukopenia (p = 0.050) and between the A1298C polymorphism and normal aspartate transaminase and alanine transaminase values (p = 0.065 and p = 0.053, respectively), which was strengthened for aspartate transaminase, after grouping the A1298A and A1298C genotypes together (p = 0.039).
MTHFR 677C>T also increased the risk of leukopenia and gastrointestinal toxicity, whilst thymidylate synthase 28 bp repeat polymorphism increased the risk of anemia (odds ratio 8.48, 95% confidence interval 2.00-36.09).