African-Americans tend to die earlier from breast, ovarian and prostate cancer than patients of other races due to biological and genetic factors, not socioeconomic ones, a study said.
The analysis was the first to find that the disparities remain even when African-American patients receive identical medical treatment and other socioeconomic factors are controlled, said the authors of the study published in the Journal of the National Cancer Institute.
Despite the strong association found between race and survival for the three gender-related cancers, the study did not identify such links for lung and colon cancer, lymphoma, leukemia and multiple myeloma.
"Patients of all races had the same doctors and received the same state-of-the-art treatments," said the study's lead author, Kathy Albain, a breast and lung cancer specialist at Loyola University's Cardinal Bernardin Cancer Center.
"It was a level playing field for everyone. So our findings cast doubt on a widely accepted theory that African-Americans' lower survival rates for certain cancers are solely due to such factors as poverty and poor access to quality healthcare."
The study examined the records of nearly 20,000 adult cancer patients who had undergone 35 clinical trials conducted by the Southwest Oncology Group, funded by the National Cancer Institute, and were followed for at least 10 years.
It found that even when receiving good treatment by the same doctors, African-American patients with breast, prostate or ovarian cancer faced a higher risk of death than other patients, ranging from a 21 percent higher risk for men with prostate cancer to a 61 percent risk for ovarian cancer in women.
The study, which included 2,500 African-American patients, or 12 percent of all participants, also found that African-American women had 49 percent higher risk of dying from early post-menopausal breast cancer than those from other races.
Before menopause, African-American women were found to have a 41 percent greater risk of dying from breast cancer.
The removal of treatment and socioeconomic factors as the cause for the higher mortality "implicates biology," said study co-author Dawn Hershman of the Columbia University College of Physicians and Surgeons.
"There may be differences in genetic factors by race that alter the metabolism of chemotherapy drugs or that make cancers more resistant or more aggressive."
The findings suggested that the survival gap between the cancers is likely due to a complex interaction between a tumor's biological factors and inherited variations in genes that control the metabolism of drugs, toxins and hormones, Albain said.