Pharmacogenomics Effects on High-Dose Methotrexate Clearance in Patients With Diffuse Large B-Cell Lymphoma

Inclusion Criteria: * \* Adult (age ≥ 18 years at diagnosis) * Diagnosis of DLBCL or PCNSL * Planned to undergo treatment with HDMTX (≥ 3 g/m\^2) at the James Cancer Hospital. Note: patients with CKD are eligible to participate regardless of eGFR provided the treating physician is planning a dose of HDMTX of at least 3 g/ m\^2. * Ability to provide informed consent. Exclusion Criteria: * \* Patients with a "currently active" second malignancy that, in the opinion of the principal investigator, will interfere with patient participation, or confound data interpretation * Pregnancy (positive serum or urine pregnancy test), lactating or breast feeding * Prisoners or incarcerated patients * Total bilirubin \> 5 mg/dL