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Cancer screening tests ineffective at identifying neuroblastoma in babies

By Jonathan Grover | April 11, 2002

Early diagnosis and cancer testing is based on a simplistic idea according to Dr. Steven Goodman, an Associate Professor of Oncology and Pediatrics at Johns Hopkins School of Medicine: "It might help, and how could it hurt?"

New studies published in the New England Journal of Medicine found that an early screening test for neuroblastoma, a deadly childhood cancer, in babies was failing to find the deadly cancer, instead finding only those that would not have been problematic.

Neuroblastoma, one of the most common of childhood cancers, is still relatively rare, occurring in only one in 7000 children under the age of five. Nonetheless it is usually fatal when found after the child is one year of age.

Thus researchers in Japan developed an early screening test that did not wait for symptoms to present themselves.

The test looked for tumors by searching for telltale chemicals in urine samples blotted from the babies' diapers. Following early detection, the cancer could be eliminated through surgery. Or so the initial premise went.

The first study, conducted in Quebec, Canada, involved virtually every baby born in the province between 1989 and 1994.

The study, directed by Dr. William G. Woods of the Aflac Cancer Center in Atlanta, and including Dr. Bernard Lemieux of the University of Sherbrooke in Quebec and Dr. Mendel Tuchman of the Children's National Medical Center in Washington, offered 476,654 children the screening test both when the kids were three weeks old and against six months old.

The test was successful at finding children with neuroblastoma, and the incidence of cancer was found to be double that of the controls.

The problem was that the death rate due to neuroblastoma did not change.

After much analysis the researchers concluded that the test was, in fact, not finding the deadly cancers, but those that would stop growing and return to normal if left alone.

The two different kinds of cancer were identical in the laboratory tests.

Researchers reasoned that perhaps it was the time of the test that was off. Perhaps researchers should be testing at one year of age, the point at which it is known that deadly tumors have begun developing.

Perhaps by that point in time, the non-deadly tumors would have begun to return to normal.

A second study, in Germany, looked at this possibility. Under the directorship of Dr. Freimut H. Schilling of Olgahospital in Stuttgart, 2,581,188 children were offered the neuroblastoma screening test at the age of one, between the years 1995 and 2000. A control population of 2,117,600 was not offered the test.

The results obtained in this study were nearly identical to those of the Quebec study.

While there was an increase in the number of cancers diagnosed, there was no significant decrease in the death rate. It was noted that of the cancers found (149), 66% (99) would have disappeared on their own.

Before this study, there had been reports of children with neuroblastoma who had seen their cancers spontaneously regress. It was believed that those were rare exceptions.

Now it is known that it is in fact the rare exceptions of neuroblastomas that kill. Most neuroblastomas are now believed to be harmless.

Nonetheless, the neuroblastoma story clearly illustrates the problems of screenings. The tests should be tested before they come into widespread use.

New tests, such as a blood test for prostate cancer, and one for lung cancer, are being put into use without having been properly evaluated.

According to Dr. Harmon Eyre, the Chief Medical Officer for the American Cancer Society, a screening test "should be tested in a randomized clinical trial, yet it is being promoted by hospitals and health care clinics around the country in settings where it has not been evaluated."

Dr. Russell Harris, an Associate Professor of Medicine at the University of North Carolina, spoke on the neuroblastoma test saying it "is the easy case, where we don't find any benefits."

But what happens when we find a screening test that leads to a small decrease in the death rate, but a dramatic increase in the number of people who underwent unnecessary treatment for non-dangerous tumors?

Dr. Harris sums this up beautifully, "What are we doing to do? And who decides?

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