The Role of Stage at Diagnosis in Colorectal Cancer Black-White Survival Disparities: A Counterfactual Causal Inference Approach.
BACKGROUND
To date, a counterfactual framework has not been used to study determinants of social inequalities in cancer. Considering the case of colorectal cancer, for which racial/ethnic differences in stage at diagnosis and survival are well documented, we quantify the extent to which black versus white survival disparities would be reduced had disparities in stage at diagnosis been eliminated in a large patient population.


METHODS
We obtained data on colorectal cancer patients (diagnosed between 1992 and 2005 and followed until 2010) from US-SEER (Surveillance, Epidemiology, and End Results) cancer registries. We employed a counterfactual approach to estimate the mean survival time up to the 60th month since diagnosis for black colorectal cancer patients had black-white disparities in stage at diagnosis been eliminated.


RESULTS
Black patients survive approximately 4.0 [confidence interval (CI), 4.6-3.2] months less than white patients within five years since diagnosis. Had disparities in stage at diagnosis been eliminated, survival disparities decrease to 2.6 (CI, 3.4-1.7) months, an approximately 35% reduction. For patients diagnosed after the age of 65 years, disparities would be halved, while reduction of approximately 30% is estimated for younger patients. Survival disparities would be reduced by approximately 44% for women and approximately 26% for men.


CONCLUSIONS
Employing a counterfactual approach and allowing for heterogeneities in black-white disparities across patients' characteristics, we give robust evidence that elimination of disparities in stage at diagnosis contributes to a substantial reduction in survival disparities in colorectal cancer.


CONCLUSIONS
We provide the first evidence in the SEER population that elimination of inequities in stage at diagnosis might lead to larger reductions in survival disparities among elderly and women.
Psychiatric Biostatistics Laboratory, McLean Hospital, Belmont, Massachusetts. Harvard Medical School, Boston, Massachusetts. lvaleri@mclean.harvard.edu.
Linda
L
Valeri
Department of Social and Behavioral Sciences, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
Jarvis T
JT
Chen
Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
Xabier
X
Garcia-Albeniz
Department of Social and Behavioral Sciences, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
Nancy
N
Krieger
Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts. Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
Tyler J
TJ
VanderWeele
Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
Brent A
BA
Coull
D001741:Black or African American / Q000706:statistics & numerical data*; D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000208:ethnology* / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D054624:Health Status Disparities; D054625:Healthcare Disparities; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D018426:SEER Program; D015996:Survival Rate; D044465:White People / Q000706:statistics & numerical data*