A woman receives cancer treatment

(CBS/AP) BOSTON - Scientists are reporting what could be very bad news for efforts to customize cancer treatment based on each person's genes.

PICTURES: Got cancer? 10 secrets for better decisions

They have discovered big differences from place to place in the same tumor as to which genes are active or mutated. They also found differences in the genetics of the main tumor and places where the cancer has spread.

This means that the single biopsies that doctors rely on to choose drugs are probably not giving a true view of the cancer's biology. It also means that treating cancer won't be as simple as many had hoped.

New treatment for kidney transplant patients may reduce need for anti-rejection drugs

By analyzing tumors in unprecedented detail, "we're finding that the deeper you go, the more you find," said one study leader, Dr. Charles Swanton of the Cancer Research UK London Research Institute in England. "It's like going from a black-and-white television with four pixels to a color television with thousands of pixels."

Yet the result is a fuzzier picture of how to treat the disease.

The study is reported in Thursday's New England Journal of Medicine.

It is a reality check for "overoptimism" in the field devoted to conquering cancer with new gene-targeting drugs, Dr. Dan Longo, a deputy editor at the journal, wrote in an editorial.

See the article here:
Gene differences in tumors making cancer treatment difficult