Genetic Factors Linked to Survival Gap for Several Cancers

African-American patients with breast, ovarian, and prostate cancer tend to die earlier than patients of other races with these cancers, even when they receive identical medical treatment, a new study says.

The finding, an analysis of almost 20,000 patient records from 35 clinical trials, points to biological or genetic factors as the potential source of the survival gap. Dawn Hershman, M.D, M.S., a Columbia University Medical Center oncologist whose research is dedicated to examining racial and ethnic disparities in cancer outcome and in cancer survivorship, was the senior author of the research published online by the Journal of the National Cancer Institute (JNCI).

The study analyzed patient records from clinical trials – going back as far as 1974 – conducted by the Southwest Oncology Group (SWOG). The investigators conducted an analysis that controlled for comparable treatment, disparities in tumor prognosis, demographics, and socioeconomic status, and found no statistically significant difference in survival based on race for a number of cancers – including lung, colon, lymphoma, leukemia and multiple myeloma. However, African-American patients with breast, ovarian, or prostate cancers – the gender specific tumors – were found to face a significantly higher risk of death than did other patients, ranging from 21 percent higher for those with prostate cancer to 61 percent higher for ovarian cancer patients.

The poorer outcome for African-American cancer patients was supported by separate data published last month in the Journal of Clinical Oncology (JCO), which found that disparities in breast cancer survival based on race persisted even after adjusting for differences in treatment. That analysis of data from 634 breast cancer patients who participated in two SWOG-conducted trials was led by first author Dr. Hershman. Findings revealed that African-American women received similar dose intensity and cumulative dose as the Caucasian breast cancer patients, but were more likely to discontinue treatment early or experience treatment delay. In addition, African-American women had lower white blood counts, but no increase in infections complications. While Dr. Hershman and her team adjusted for these specific treatment related factors and other known predictors of outcome, such as age, hormone receptor status, stage, and treatment, African-American women still faced a lower rate of survival.

"The findings from these two studies are important as they suggest a possible role for biologic factors such as genetics, hormonal factors, comorbid conditions and tumor biology in cancer disparities. A better understanding of all the factors that contribute are critical, so that continued progress can be made toward reducing cancer mortality for patients of all races and ethnicities," says Dr. Hershman, assistant professor of medicine and epidemiology at Columbia University Medical Center and co-director of the breast cancer program at the Herbert Irving Comprehensive Cancer Center at NewYork-Presbyterian Hospital/Columbia University Medical Center. "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. We are now starting research to determine the role of these factors in this disparity."

"When you look at the dialogue about the issue of race and cancer survival that has gone on over the years, it always seems to come down to general conclusions that African-Americans 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," says Kathy Albain, M.D., of Loyola University's Cardinal Bernardin Cancer Center, lead, and senior author of the JNCI and JCO papers, respectively. "The good news is that for most common cancers, your survival is the same regardless of race. But this is not the case for breast, ovarian, and prostate cancers."

"The need to address the racial disparities in cancer survival outcomes – both sociological and biological – has never been more urgent," says Dr. Hershman. "With the incidence of cancer among minorities predicted to double in the next two decades – while comparable incidence among whites is only expected to rise 31 percent – this is a crucially important public health issue to understand all the factors that alter survival outcomes."

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Source-Eurekalert
RAS