An analysis of almost 20,000 patient records from the Southwest Oncology Group’s database of clinical trials finds, for the first time, that African American breast, ovarian and prostate cancer patients tend to die earlier than patients of other races even with identical medical treatment and other confounding socioeconomic factors as controls. The finding points to biological or host genetic factors as the potential source of the survival gap.
The study, published by the Journal of the National Cancer Institute (JNCI), found that when treatment was uniform and differences in tumor prognostic factors, demographics and socioeconomic status were controlled, there was in fact no statistically significant difference in survival based on race for a number of common cancers—lung, colon, lymphoma, leukemia and multiple myeloma. However, this is not the case for breast, ovarian and prostate cancers, said the paper’s lead author Dr. Kathy Albain, a breast and lung cancer specialist at Loyola University’s Cardinal Bernardin Cancer Center.
“When you look at the dialogue about the issue of race and cancer survival that’s gone on over the years it always seems to come down to general conclusions that African Americans may in part have poorer access to quality treatment, may be diagnosed in later stages, and may not have the same standard of care delivered as Caucasian patients, leading to a disparity in survival,” she said.
However, the elimination of treatment and socioeconomic factors as the cause of this higher mortality in the sex-specific cancers “implicates biology,” said study co-author Dr. Dawn Hershman of the Columbia University College of Physicians and Surgeons.
“Our study of multiple cancers is distinguished from others that have looked at race-based disparities by its size and by the source of its data,” said Joseph Unger of the Southwest Oncology Group’s Statistical Center, based at the Hutchinson Center. Unger served as statistician and co-author on the JNCI study.
The study analyzed records from 35 clinical trials—going back as far as 1974—that had been conducted by the Southwest Oncology Group, a National Cancer Institute-sponsored cooperative group headquartered at the University of Michigan. "The clinical trials setting represents a fundamentally different type of database that has unique properties," Unger said, noting that using data from clinical trials, which are already controlled for a range of potentially confounding factors such as differences in diagnosis, treatment, and follow-up, helps throw the remaining factors into sharper relief.
Even with good treatment by the same doctors, African American patients with breast, ovarian and prostate cancers faced a significantly higher risk of death than did other patients, ranging from a 21 percent higher risk for those with prostate cancer to a 61 percent higher risk for ovarian cancer patients. Unger and colleagues said that the elimination of treatment and socioeconomic factors as the cause of this higher mortality “implicates biology.” Adding “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 urgency of addressing the reasons for racial disparities in outcomes—both sociological and biological—is amplified by another recent study in the Journal of Clinical Oncology. It predicts the cancer incidence among minorities will nearly double in the coming decades, increasing 99 percent by 2030 compared to an expected 31 percent increase among Caucasians.
Dr. John Crowley, of the SWOG Statistical Center at the Center, and Dr. Charles Coltman, of the University of Texas Health Science Center, were also co-authors of the NCI-funded study.
[Adapted from a Southwest Oncology Group news release.]