African-American patients with resected stage II and stage III colon cancer experienced worse overall and recurrence-free survival compared to whites, but similar recurrence-free intervals, according to a study published Oct. 12 in the Journal of the National Cancer Institute.
Colorectal cancer is a leading cause of cancer-related deaths in the United States. In 2006, there were an estimated 146,970 new cases of colorectal cancer diagnosed in the U.S. Of those diagnosed, 15,000 were projected to occur in individuals of African ancestry, resulting in approximately 7,000 deaths. Despite overall improvements in colorectal cancer survival in the U.S., the survival difference between African-Americans and whites has not narrowed. The 5-year relative survival rates for black and white colorectal cancer patients between 1999 and 2005 were 57% and 68%. Although several causes of the disparities have been identified, the reasons are not well understood.
In order to determine the disparities of colorectal cancer survival outcomes between blacks and whites, Greg Yothers, Ph.D., of the National Surgical Adjuvant Breast and Bowel Project Biostatistical Center and colleagues, examined data from the Adjuvant Colon Cancer ENdpoinTs (ACCENT) collaborative group database to analyze 14,611 African-American and white patients with stage II or III colorectal cancer enrolled in 12 phase III randomized controlled clinical trials conducted in North America from 1977-2002. Within these trials, patients received the same adjuvant colon cancer therapy regardless of race, but care for other diseases or recurrent colon cancer was outside the scope of these trials. The researchers evaluated overall survival, recurrence-free survival (time to recurrence or death), and recurrence-free interval (time to recurrence).
The researchers found that the five-year overall survival rate was worse among the 1,218 African-American patients, compared to the whites, with a 4.6 percentage point decrement in 5-year survival, and a 3.7 percentage point decrement in recurrence-free survival. But there was no statistically significant difference in recurrence-free interval.
The authors write that the survival differences are most likely because of factors unrelated to a patient's response to adjuvant treatment. "Black patients with resected stage II and III colon cancer treated with identical adjuvant therapy experienced poorer overall and recurrence-free survival but similar recurrence-free interval compared with white patients," they write. "Biological differences, differences in general health, and disparities in health care outside the clinical trial are possible explanations for these findings "
In an accompanying editorial, Olufunmilayo I. Olopade, M.D., Director of the Center for Clinical Cancer Genetics & Global Health at the University of Chicago, and colleagues write that the Yothers study is consistent with studies published in the last decade. "When treated equally, African-Americans have similar colon cancer-specific survival but continue to have poorer overall survival compared with white patients," they write. Going forward, trials must include basic information on patients' socio-demographic situation, as well as their tumor biology and co-morbid conditions, the editorialists write, adding that primary care of survivors should also be improved and monitored so that differences in survival after recurrence can be better understood. Lastly, trials examining genetic markers may require enrolment targets, so that a trial could close to accrual for whites but may remain open for African-Americans and other minorities. The editorialists write, "We have documented racial and ethnic differences in cancer survival by looking from 10,000 feet over the past decade, but it is past time for us to get out of the clouds and collect and integrate data that advance the field."
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