Purpose/Objective(s): Outcomes in racial disparities among cancer patients (pts) is established. The specific aim of this study was to determine if RT delivery differed by race as measured by total dose, duration of RT, and dose-intensity (DI), in a major cooperative group dataset.

Methods and Materials: 9,646 Caucasian (C) pts & 1,040 African-American (AA) pts were enrolled in NSABP breast cancer protocols: B15, B16, B18, B22, B23, B25, & B28. Adjuvant AC was given in all protocols. Within the total cohort, 3,504 C pts & 377 AA pts received RT. Statistical methodology: Logistic regression was used as the method of analysis. The dependent, or outcome, variables were binary (Y/N): total dose at least 5,000 Gy, RT duration < 35 days, & DI at least 142.86 (= 50 Gy/35 days). The primary predictor variable was race (AA vs C). Potential confounder variables considered were race, age, no. of positive nodes (0,1-3,4-9,10+), completion of 4 cycles of AC (Y/N), pathologic tumor size, & protocol. Association between race & outcome was initially assessed without adjustment. Next, logistic regression models were constructed in a forward stepwise fashion, considering the above potential confounder variables in turn, using α = 0.05 for entry & removal. For all 3 outcomes, the only potential confounder variable that reached significance in the stepwise analysis was protocol. Finally, race & race-by-protocol interaction were added to the models & assessed for statistical significance.

Results: Most pts completed the recommended dose [n=331 AA (87.7%); 3,182 C (90.8%)] within the recommended number of days (< 35) per protocol [327 AA (86.7%), 3,096 C (88.3%)] & received the appropriate Dl [296 AA (78.5%), 2,860 C (81.6%)]. Race was not a significant univariate predictor for total dose (p=0.06, 0R=0.73; 95% Cl=0.52−1.01) & did not reach significance after adjustment for protocol (p=0.07, 0R=0.73, Cl=0.52−1.02). Race was not a predictor for completion of RT within 35 days (p=0.35, 0R=0.86, Cl=0.63 −1.18) & remained non-significant after adjustment for protocol (p=0.51, 0R=0.90, Cl=0.66–1.23). As a univariate predictor of RT Dl, race was not significant (p=0.16, 0R=0.83, Cl=0.64–1.08). After adjustment for protocol, race remained non-significant (p=0.25, 0R=0.86, Cl=0.66–1.12). The interaction between race & protocol was non-significant for all outcomes.

Conclusions: Randomized trials guide evidence-based approaches for breast cancer treatment. This study did not find evidence of racial disparity in the delivery of RT in NSABP breast cancer trials examined.

Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):B116.

Copyright © September 30, 2010, American Association for Cancer Research
2010