Factors associated with the use of immunochemotherapy rather than chemotherapy alone for PCNSL. (A) Number of patients receiving either treatment options each year. (B) Association between age and the probability of receiving immunotherapy (fitted line from a fractional polynomial fit; markers are sized according to the number of patients in each age group). (C) Association between HIV status, race/ethnicity, and receipt of immunochemotherapy; the interaction test between HIV and race/ethnicity was not statistically significant (P = .31); note that data for patients tested positive for HIV of Asian or other race/ethnicity are suppressed per the NCDB policy (<11 patients). (D) Association between facility volume (expressed as the average number of PCNSL cases per year reported to NCDB) and frequency of immunochemotherapy use (fitted line from a fractional polynomial fit; markers are sized according to the number of patients in each age group).