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Outcomes in White Patients and those of African Descent Receiving Adjuvant Therapy for Colon Cancer. Greg Yothers, William Blackstock, Norman Wolmark, Richard M Goldberg, Michael J. O’Connell, Jacqueline Benedetti, James Dignam, and Daniel J. Sargent for the ACCENT collaborative group
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Outcomes in White Patients and those of African Descent Receiving Adjuvant Therapy for Colon Cancer Greg Yothers, William Blackstock, Norman Wolmark, Richard M Goldberg, Michael J. O’Connell, Jacqueline Benedetti, James Dignam, and Daniel J. Sargent for the ACCENT collaborative group ASCO Gastrointestinal (Colorectal) Cancer, Poster Discussion Session, June 2, 2007 2-6 PM
Background Published reports suggest that colon cancer patients of African descent have inferior survival compared to White patients. Whether these differences are explained by clinical factors at diagnosis, socioeconomic factors impacting access to care, or intrinsic differences in the biology of the tumors or the response to therapy is unclear. Patients in clinical trials have data collected for important baseline clinical factors and should receive comparable oncologic care regardless of socioeconomic factors.
Methods We analyzed data from 13,435 individual patients on 11 phase III adjuvant colon cancer trials accrued from 1977 to 2002. Analysis was restricted to stage II and III patients, with race reported as Black or White. Endpoints were: Overall Survival (OS-time to death) Recurrence-Free Survival (RFS-time to recurrence or death) Recurrence-Free Interval (RFI-time to recurrence censor death) Multivariate Cox Proportional Hazard models stratified by study controlled for gender, stage, age, and treatment type to determine the effect of race. Kaplan-Meier estimates were adjusted by the Xie-Liu method for study, gender, stage, age, and type of treatment.
Patient Characteristics * Chi Square test
Results • African American patients (n=1134, 8.4%) were younger than White patients (median 58 vs 61, p<0.001) and more likely female (55 vs 45%, p<0.001). • AfricanAmerican patients had poorer Overall Survival than White patients (p<0.0001, HR= 1.22, 95% CI 1.11-1.34). • Overall Survival results were consistent in subsets defined by gender, stage, and age. • Recurrence-Free Survival results were attenuated compared to Overall Survival , but still favored improved RFS in White patients (p=0.0029, HR= 1.15, 95% CI 1.05-1.26). • Recurrence-Free Interval results were further attenuated and not significantly different by race (p=0.1194, HR= 1.09, 95% CI 0.98-1.21).
Multivariate Cox Models * * Models also controlled for Treatment Type (data not shown)
Adjusted Kaplan Meier Estimates Overall Survival Group Black White HR (95% CI) 1.22 (1.11-1.34)1.00 (Ref.) Died (%) 485 (43) 4702 (38) P-value < 0.0001 Total 1134 12301 622 307 63 7450 3523 531 Numberat Risk:
Adjusted Kaplan Meier Estimates Group Black White Total 1134 12301 Events (%) 521 (46) 5243 (43) HR (95% CI) 1.15 (1.05-1.26)1.00 (Ref.) P-value 0.0029 Numberat Risk: 579 295 62 6766 3338 510
Adjusted Kaplan Meier Estimates Recurred (%) 384 (34) 3939 (32) Group Black White Total 1134 12301 HR (95% CI) 1.09 (0.98-1.21)1.00 (Ref.) P-value 0.1194 Numberat Risk: 579 295 62 6766 3338 510
Forest Plots INT-0035 NCCTG-89-46-51 NCCTG-91-46-53 S9145 NSABP-C01 NSABP-C02 NSABP-C03 NSABP-C04 NSABP-C05 NSABP-C06 NSABP-C07 All Trials - Pooled All Trials - Stratified ← Favors Blacks ← Favors Blacks → Favors Whites → Favors Whites OS RFI RFS 0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 0.5 1.0 1.5 2.0 Hazard Ratio
Conclusions • Even with identical treatment for colon cancer in controlled clinical trials, AfricanAmerican patients have poorer Overall Survival and Recurrence-Free Survival than White patients. • The Overall Survival deficit was consistent across subgroups, and neither deficit was explained by differences in gender, stage, age, or treatment type. • Recurrence-Free Interval was similar for both races, suggesting that the Overall Survival and Recurrence-Free Survival differences may be largely due to deaths unrelated to colon cancer.