Patients of African American descent with metastatic colorectal cancer are less likely to be seen by cancer specialists or receive cancer treatments, according to researchers. This difference in treatment explains a large part of the 15% higher mortality seen in African American patients than non-Hispanic white patients.

The study, published online in the Journal of the National Cancer Institute (2013; doi:10.1093/jnci/djt318), noted there was no difference in mortality risks 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 the Moores Cancer Center at the University of California at San Diego.

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The researchers analyzed data from 11,216 patients older than 66 years 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. The disease affects black patients disproportionately 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% less likely to have primary tumor surgery, 17% less likely to receive chemotherapy, and 30% 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 4 days later than white patients. Chemotherapy was associated with a 66% decrease in risk of death.

“Of note, our analysis found that 47% 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, health care 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.”