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Dose intensity comparison of African-American and white patients in NSABP breast treatment trials of postoperative doxorubicin and cyclophosphamide.

6111 Background: It has been proposed that ethnic neutropenia in African-American (AA) breast cancer patients leads to lower chemotherapy dose intensity (DI) compared to white (W) patients and hence to increased mortality from the disease [Hershman 2003]. Thomas et al. [2005] confirmed that AA patients in NSABP breast treatment trials had lower WBC and ANC than W counterparts and found that the total amount of chemotherapy received was no different in AA and W patients. The aim of the present study was to extend previous work to determine whether postop doxorubicin (A) and cyclophosphamide (C) DIs (as opposed to total doses) were lower in AA pts enrolled in NSABP breast cancer adjuvant treatment trials.


METHODS
Pooled data from AA and white (W) pts enrolled in NSABP trials B-15, B-16, B-18 (postop pts only), B-22, B-23, and B-25 (N=10,678 total: 1,040 AA pts and 9,638 W pts) were analyzed. Outcome measures were 1) total A received as a % of the total dose projected on the basis of BSA divided by total days of chemotherapy and 2) corresponding % of C divided by total days of chemotherapy. These quantities were compared in AA and W pts using ANOVA with adjustment for protocol, BMI, G-CSF use, C regimen (600mg/m2 ×4, 1200mg/m2 ×2, 1200mg/m2 ×2, 2400mg/m2 ×2, 2400mg/m2 ×4), and significant pairwise interactions among these variables.


RESULTS
After adjustment for the above-listed factors, AA was not a significant predictor of dose intensity for either A or C (p = 0.24 for both comparisons).


CONCLUSIONS
This retrospective exploratory analysis suggests that despite lower baseline WBC and ANC, AA pts enrolled in these NSABP trials did not receive substantially lower A and C DI than did W pts. Recommending identical dose regimens for AA and W patients in AC-based breast treatment trials is thus most likely clinically reasonable. No significant financial relationships to disclose.