This difference in treatment explains a large part of the 15 percent higher mortality experienced by African-American patients than non-Hispanic white patients.
The study, published online in the Journal of the National Cancer Institute
, noted there was no difference in risk of death when black patients received the same treatments, such as chemotherapy and surgery, as non-Hispanic white patients.
"Other studies have looked at racial disparities in treatment and still others have focused on racial differences in survival rates of cancer patients, but our research attempted to go further by demonstrating the impact of race-based inequalities in cancer treatment on survival rates of black colorectal cancer patients," said James D. Murphy, MD, MS, assistant professor and chief of the Radiation Oncology Gastrointestinal Tumor Service at UC San Diego Moores Cancer Center.
The researchers analyzed data from 11,216 patients over the age of 66 with stage IV colorectal cancer from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database. The analysis compared patient consultation rates with cancer specialists as well as treatment with surgery, chemotherapy and radiation therapy for white and black patients.
Despite screening efforts and improvements in treatment, colorectal cancer is the third leading cause of cancer death in the United States, according to the American Cancer Society, with approximately 50,000 deaths annually. This disease disproportionally affects black patients, with higher incidence rates, more advanced stage at diagnosis and decreased survival rates compared to other ethnic groups.
The study concluded that black patients were 10 percent less likely to have primary tumor surgery, 17 percent less likely to receive chemotherapy and 30 percent less likely to receive radiotherapy. Among patients who received chemotherapy, white patients were more likely to receive more than one chemotherapy agent. The researchers noted that black patients typically received chemotherapy four days later than white patients. Chemotherapy was associated with a 66 percent decreased risk of death.
"Of note, our analysis found that 47 percent of the relative survival difference between black and white patients was attributable to treatment differences and, after accounting for these treatment differences, the race-based survival difference completely disappeared," wrote the study authors.
The study did not ascribe a specific cause for the racial disparities but offered six possible explanations: conscious or unconscious provider biases; patient mistrust; health literacy; patient-physician communication breakdown; healthcare access barriers; and/or race-based differences in disease biology.
"Further studies may answer the important question of why there are racial disparities in consults with cancer specialists and treatment among this population. The answers may lead to areas we can improve upon to close these gaps," said Murphy. "I suspect that this pattern of disparity could be present in other underserved minority groups as well."