Race and Intensity of Post-Remission Therapy in Acute Myeloid Leukemia (AML).

Disparities in survival between black and white patients (pts) exist for many malignancies, including AML. Potential causes include differential access to care; variable aggressiveness of therapy; and biological heterogeneity. Black men with AML have lower complete remission (CR) and overall survival (OS) rates than black women and whites, as shown in a previous Cancer and Leukemia Group B (CALGB) study in which induction therapies were defined, but subsequent treatment compliance and intensity was unknown. We investigated whether differences in post-remission therapy (PRT) might explain disparity in outcome.

All pts with newly diagnosed AML treated with cytarabine-based induction therapy between 1997 and 2008 were included. PRT was defined as either cytarabine-based chemotherapy or bone marrow transplant (autologous or allogeneic) administered to pts achieving a CR and prior to relapse or in the setting of no relapse. PRT was coded according to intensity, in cumulative mg/m² of cytarabine or mitoxantrone received, with BMT assigned the highest intensity of cytarabine. Data on known prognostic factors (age, white blood cell count (WBC) at diagnosis, pathologic subtype, AML etiology, cytogenetic risk groups (as defined by CALGB 8461)) were collected and controlled for in multivariable analyses. Time to PRT was measured in days from date of discharge after induction chemotherapy to date of PRT initiation, excluding patients with time to PRT >150 days, considered too long to be true consolidation. Comparisons between black and white pts were performed using linear, logistic, and proportional hazard regressions, exploring intensity of and time to PRT, and number of PRT cycles, along with potential interaction terms, controlling for known prognostic factors for outcome.

Of 460 pts, 421 had adequate data on PRT. Of these, 379 (90%) were white, 32 (8%) black, 10 (2%) other, and 46% were female. Similar to CALGB data, and compared to whites, blacks were younger (mean age 53.5 vs. 57.5 years, p=.11), had a higher proportion of favorable (18.8% vs. 12.7%) and poor risk (34.4% vs. 24.5%) cytogenetics (p=.28), and were less likely to attain a complete remission (CR, 66% vs. 73%, p=.39), though differences did not reach significance due to sample size. Other baseline characteristics, including reinduction rates, were similar. The 236 pts who received PRT included 18 blacks (56%) and 218 whites (58%, p=.89). In univariate analyses, for blacks vs. whites, median time to PRT initiation was 31 vs. 23 days (p=.33); cytarabine intensity was 66,654 mg/m² vs. 50,630 mg/m² (p=.26); and number of cycles was 2.4 vs. 2.1 (p=.41), respectively. Median time to PRT among all men was 24 days, compared to 21 days for all women (p=.09), and for pts <60 years was 22 days, vs. 24 days for >=60 years (p=.43). Median survival was 0.72 years in both black and white patients (p=.57). Among those receiving PRT, median survival was 3 years in blacks and 1.4 years in whites (p =.22); for pts not receiving PRT, median survival was.22 years in blacks and.32 years in whites (p =.25). In multivariate analyses, time to PRT was shorter for whites (HR=.25, p=.016), particularly when white men were compared to black men (HR=.12, p=.012), whereas no differences were found for women. Survival differences did not reach significance; nor was there an interaction for male and black race.

Time to PRT is shorter for whites compared to blacks with AML, though cycle dose intensity and number are similar. Despite this, overall survival was not different between blacks and whites receiving PRT. In the post-remission setting, blacks and whites appear to receive similar chemotherapy management, and thus differential treatment aggressiveness and compliance are not explanations for varying outcome between races.

No relevant conflicts of interest to declare.