Differential impact of sex in young and elderly patients with DLBC: Correlation with rituximab (R) pharmacokinetics.

Abstract

8570 Background: Sex and weight independently influence R clearance in elderly DLBCL pts (Mueller et al., Blood 2012). Methods: We analyzed the impact of sex on R pharmacokinetics and outcome of 1,222 elderly pts of the RICOVER-60, 823 young (18 to 60 years) aaIPI=0,1 pts of the MInT, and 375 aaIPI=2,3 pts of the Mega-CHOEP trials. R pharmacokinetics was determined by ELISA in 33 young and 49 elderly patients. Population pharmacokinetic modeling was performed with nonlinear mixed-effect modeling software (NONMEM VI). Results: R clearance was independent of tumor mass (IPI), but weakly correlated (0.2, R2linear=0.045) with increasing age in male, and moderately inversely correlated (-0.5, R2linear=0.207) with age in female DLBCL patients, resulting in similar R clearances in young female and male patients (9.88 vs. 10.38 ml/h; p=0.238), but a significantly faster R clearance in elderly males compared to females (10.50 vs 8.25 ml/h; p=0.006). In the RICOVER-60 trial, elderly females had a higher 3-year PFS (68% vs. 61%) and OS (74% vs. 68%) than male pts. due to a greater outcome improvement by the addition of R in females. In a multivariable analysis adjusting for IPI, the hazard for progression in male compared to female pts. was not significantly increased after CHOP (HR=1.1; p=0.348), but was significantly higher after R-CHOP (OR=1.6; p=0.004). In contrast, young males treated in the MInT and Mega-CHOEP trials benefitted as much as females from the addition of rituximab, with a similar hazard for male pts. after CHOP and R-CHOP (HR=1.2) with no significant difference to female patients (HRPFS=1.2, p=0.552; HROS=1.0; p=0.898). Conclusions: While no differences in R clearance and benefit from rituximab were found in young female compared to male patients, the reduced benefit of adding R to CHOP in elderly male DLBCL pts. who have a shorter rituximab serum half life and hence lower serum levels suggests that this subpopulation is suboptimally dosed when R is given based on body surface area at 375 mg/m2. Ongoing studies of the DSHNHL investigate whether higher R doses for pts. with a shorter R serum half life can improve the outcome of the respective patients. Supported by Deutsche Krebshilfe and Roche.