Cancer Prognoses Favor the Rich and Well-Educated

By Crystal Phend
DENVER, 24 june 2008 -- Cancer is crueler to minorities and others in lower socioeconomic brackets, according to a large population-based study.
Such cancer patients, commonly those with less education, had more advanced disease at diagnosis, got less aggressive treatment, and were more likely to die in the five years after diagnosis, reported Tim E. Byers, M.D., M.P.H., of the University of Colorado here, and colleagues in the Aug. 1 issue of Cancer.
A more aggressive tumor biology among patients from minority racial and ethnic groups may explain some of the associations with low income and education, the researchers said.
"Social factors, however, seem to be more important than biologic factors in explaining racial and ethnic cancer disparities," they said.
The researchers analyzed data from the Breast, Colon, and Prostate Cancer Data Quality and Patterns of Care Study that included a sample of patients from state cancer registries in California, Colorado, Illinois, Louisiana, New York, Rhode Island, and South Carolina.
The study included 4,844 breast cancer patents, 4,422 colorectal cancer patients, and 4,332 prostate cancer patients diagnosed in 1997. About 80% of these patients were non-Hispanic white, and more than half were older than 65.
Neighborhood-level census track data from 2000 was used to classify patients as living in a low socioeconomic status area according to whether less than 25% of adults in the area had a high school education, whether 20% or more of households had incomes below the Federal Poverty Level, or both.
Cancer patients who lived in a low socioeconomic status area were more likely to be diagnosed at an advanced stage than those in well-to-do areas. These findings included:
For breast cancer, regional disease was present in 23% versus 20% while distant metastasis was present in 4-6% versus 3% depending on the criteria for low socioeconomic status.
For prostate cancer, regional disease was present in 10% versus 9% while distant spread was present in 6% versus 4%.
For colorectal cancer, the associations of socioeconomic status with stage and all-cause mortality were not significant. It was a risk factor, though, for mortality among colorectal cancer patients younger than 65 (hazard ratio 1.37, 95% confidence interval 1.11 to 1.68).
"That this disparity disappeared after age 65 years may reflect an effect of Medicare coverage," the researchers suggested.
All-cause mortality was linked to socioeconomic status as well among breast cancer patients in models adjusted for age (HR 1.59, 95% CI 1.35 to 1.87) and when controlling for race or ethnicity (HR 1.33, 95% CI 1.11 to 1.58), although the association was no longer significant in the fully adjusted model (HR 1.16, 95% CI 0.97 to 1.38).
For prostate cancer, low socioeconomic status increased mortality when controlling for age (HR 1.33, 95% CI 1.13 to 1.57) though statistical significance was lost after adjustment for race and ethnicity (HR 1.17, 95% CI 0.98 to 1.40).
The association between mortality and socioeconomic status was stronger among minorities than among non-Hispanic whites for both breast cancer (HR 1.52 versus 1.11) and colorectal cancer (HR 1.28 versus 1.10).
For all three cancer groups, socioeconomic status appeared to impact treatment. Findings for patients in poorer areas with less education, compared with other areas, included:
Women with localized breast cancer and low socioeconomic status were more likely to have a mastectomy (46%-49% versus 38%).
Women who underwent lumpectomy were less likely to get adjuvant radiotherapy (77% versus 60%, P≤0.001).
Women with regional-stage breast cancer were slightly less likely to get adjuvant chemotherapy (68% versus 63%, P=0.16).
Women with hormone receptor-positive breast cancer were slightly less likely to get antiestrogen therapy (58% versus 52%, P=0.08).
Patients with regional-stage colon cancer were less likely to get adjuvant chemotherapy (56% versus 50%, P=0.02).
Men with prostate cancer were less likely to get prostatectomy or radiation (78% versus 67%, P≤0.0001).
The researchers noted that their study might have been limited by looking at all-cause rather than cancer-specific mortality and by use of neighborhood-level rather than individual socioeconomic status.
Race and ethnicity are often used as proxies for modifiable socioeconomic factors, such as health insurance, but this should change given the increasing evidence from this and other studies that a substantial proportion of disparities in cancer can be attributed to socioeconomic status, Dr. Byers and colleagues said.
"Better information on how cancer outcomes are related to socioeconomic status is needed if we are to properly identify and address the root causes of racial and ethnic cancer disparities in the United States," they wrote.
The study was supported by cooperative agreements between the CDC and the states of California, Colorado, Illinois, Louisiana, New York, Rhode Island, and South Carolina. The researchers reported no conflicts of interest.
Primary source: CancerSource reference:Byers TE, et al "The impact of socioeconomic status on survival after cancer in the United States: findings from the national program of cancer registries patterns of care study" Cancer 2008; 113.