Researchers know that cancer treatment outcomes vary based on patients’ racial backgrounds. And they’ve long pointed to social and economic factors as the main reasons. New research suggests the story may be more complicated.

Survival varies by race for liver cancer patients who undergo liver transplantation to treat their disease.

Joseph Kim, M.D., assistant professor of surgery, and his colleagues analyzed data from about 24,000 liver cancer patients nationwide. His aim: to identify potential reasons that outcomes were different for different racial groups.

Survival rates for liver cancer overall have improved over the years. The progress may be due to advances in surgical technique, new targeted therapies and increased use of liver transplantation to treat early-stage tumors, Kim said.

However, the team found that survival has improved for some patients more than others, even when the patients receive comparable levels of treatment.

African-American and low-income patients had the poorest outcomes. Specifically, African-American patients had a 15 percent higher risk of death compared to Caucasian patients. And Asian-American patients did better: Their risk of death was 13 percent lower than Caucasian patients.

The team wondered if differences in access to care might have led to the differences in survivorship, Kim said, but they still found unequal outcomes by race even with equal treatment.

Digging deeper, Kim studied more than 4,000 records of liver cancer patients who underwent liver transplantation as part of their treatment. Despite similar care, African-Americans had the worst outcomes after transplantation, with a median survival of just over 30 months. Caucasian patients survived more than double that, while Asian-Americans survived nearly six years. Latinos fared best of all, with a median survival of almost seven years.

Although reasons for the disparities are hazy, researchers believe that differences in underlying disease may play a part in outcomes.

“It is clear that access, while still an important factor, is not the primary factor in the outcome disparities we see among the different racial and ethnic groups,” said Kim. “What we are learning is that in addition to providing the best treatment, we also need to pay more attention to post-treatment variables in our overall survivorship care.”

Kim and colleagues are now studying the role genes may play in outcome differences.