A new study conducted by a Yale-New Haven Hospital researcher has found that the survival rate for black, Native American and Hispanic children with leukemia is lower than that of Asian and white children, even with the most modern cancer therapies.

Principal researcher Nina Kadan-Lottick, M.D., examined the long-term survival rates for 5,000 children under the age of 20 diagnosed with Acute Lymphoblastic Leukemia, the most common childhood cancer with an incidence rate of 1.4 in 10,000. Survival rates were 1.5 times worse for black children and 1.8 times worse for Hispanic children.

In conjunction with Drs. Kirsten K. Ness and James G. Gurney of the University of Minnesota, and Dr. Smita Bhatia of the City of Hope National Medical Center in Calif., Kadan-Lottick used the National Cancer Institute’s Standardized Epidemiology End Result (SEER) database, collected from nine cancer centers nationally, to examine survival rates in children of various races and ethnicities.

Kadan-Lottick said the study has the advantage of a wide, randomized sample, but lacks the specificity to determine the cause of this discrepancy. Possible explanations might be the varying biological nature of cancers in different races, which would dictate the aggressiveness of cancer cells and response to treatment. Another explanation under consideration is unequal access to medical care.

“This is national data that includes all children diagnosed at these national centers, and not specific to children enrolled in clinical trials or enrolled in specialized centers,” Kadan-Lottick said. “However we don’t have the data to answer the questions — whether there are biological differences in the leukemia, or different response to care, or availability of medical care.”

The study will not have implications for clinical medicine until the source of the discrepancies is determined.

“In childhood cancer we have learned never to base future therapy on one or two cases, but to base it only on large national studies,” Kadan-Lottick said. “It’s not to convert this step to clinical practice, but to understand why there are discrepancies. It’s important to understand the biology of the leukemia.”

Pediatric oncologist and hematologist at Yale-New Haven Hospital, Jack Van Hoff, M.D., said he believes the discrepancy is due to differing biological nature of the cancer in various races and ethnicities, and is not the result of unequal medical care.

“I feel that as a pediatric oncologist, no one of different races gets different care in the hospital or by the nursing staff,” Van Hoff said. “But it’s certainly an area for further study.”

Van Hoff also said there is a much higher incidence of leukemia in white children than in black children — occurring at different stages in development — which provides more evidence of biological differences in the cancer.

Various studies on the subject have recently been published, many with different findings.

One such study was recently completed at St. Jude Children’s Research Hospital in Memphis, Tenn. The study found that survival rates for both white and African American children with leukemia were approximately equal. Researchers at the facility found that survival rates after 10 years were 86.2 percent for black children and 80.3 percent for white children, according to the published report on the St. Jude web site.

Dr. Ching-Hon Pui, director of the St. Jude Leukemia/Lymphoma division, attributed the results to the hospital’s specialization in this area.

“We are helping to treat more leukemia patients than any center in the U.S., so we are more experienced,” Pui said. “So we are not on the learning curve.”

Kadan-Lottick said she considers the studies complementary. But she said patients are sent to St. Jude’s by referral from all over the country, and represent a narrower, self-selected sample.

“St. Jude’s may not be representative of the nation, because it’s so specialized and referral based,” Kadan-Lottick said. “Children that make their way to St. Jude’s are likely prone to participation bias, or in other words, that they may differ in ways from the average child because their family is one willing to go many states away for treatment — and search out that care because it’s free.”

Kadan-Lottick’s next project will examine the cause for the discrepancy. She will work with Gurney and Bhatia to examine the varying biological nature of cancers, and differing patient responses to treatment. Researchers will also examine compliance with therapy, tracking how much medication their patients take and if medicine refills are obtained.