New Tool Could Help Determine Cancer Treatment

One hallmark of aggressive cancer tumors is that they have an unusual number of chromosomes. If doctors knew which tumors had unexpected numbers of chromosomes, they'd know which tumors to treat aggressively. Now researchers have found an easy way to estimate the number of chromosomes.

STEVE INSKEEP, host:

Treating cancer involves making a lot of decisions. You have to decide if you want to treat the cancer aggressively, go in for the most extensive surgery, a full course of chemotherapy and the strongest radiation a patient can tolerate even with all the side effects, or if you can get by with less. If doctors knew in advance how likely a cancer was to spread, those decisions would be a lot easier.

Now researchers in Boston have come up with a tool that may provide that information. Here's NPR's Joe Palca.

JOE PALCA reporting:

When a normal cell becomes a cancer cell, a lot of strange things happen.

One of them is the cell loses the ability to maintain the proper number of chromosomes. So instead of the normal 46 chromosomes, that's 23 pairs, a cancer cell might have some completely wild number, like 63 or 72.

Zoltan Szallasi is a senior research scientist at Children's Hospital in Boston. He says some cancer tumors do have the right number, or nearly the right number of chromosomes.

Mr. ZOLTAN SZALLASI (Senior Researcher, Children's Hospital, Boston): Those tend to behave in a very benign fashion. Those can be treated relatively easily and the survival time is long.

PALCA: But the tumors with the wild number of chromosomes are a different story.

Mr. SZALLASI: Those are the tumors that spread very quickly and it's much more difficult to treat them, and the expected survival time is much shorter.

PALCA: So Szallasi says it would be useful to get a handle on how much chromosomal instability there was in a particular tumor.

Mr. SZALLASI: The problem was how to measure it easily.

PALCA: Traditional methods are labor intensive. You have to get cells out of the tumor, stain them with special chemicals so you can see the chromosomes, and then use a microscope to count the chromosomes.

Mr. SZALLASI: So what we came up with is a method by which we can estimate the level of chromosomal instability in cancer.

PALCA: The method takes advantage of the fact that lately scientists have come up with technology that makes it very easy to measure how genes change what they're doing inside cells. Szallasi says he and his colleagues have found a group of 25 genes that are related to chromosomal instability. The way these genes express themselves inside a particular tumor tells you how much chromosomal instability there is in that tumor.

Mr. SZALLASI: The lung cancer, tumors of the central nervous system, we believe that actually this method is pretty generalizable for most solid tumors.

PALCA: Szallasi's work appears in the online edition of Nature Genetics.

But research oncologist Luis Diaz says it will be awhile before Szallasi's method becomes useful to doctors. Diaz is at the Johns Hopkins medical school. He says cancer doctors are already pretty good at predicting which cancers will spread. To be really useful, a test that measure chromosomal instability will also have to give some clues about which treatment options to pick.

Mr. LUIS DIAZ (Research Oncologist, Johns Hopkins University): For instance, treat with this drug and these patients will do better. Or, you don't need to treat with this toxic chemotherapeutic, because these patients are going to do fine.

PALCA: Diaz is more impressed by the group of 25 genes Szallasi described in his study that were related to chromosomal instability.

Mr. DIAZ: What this gives us is a snapshot of which genes are over expressed in these cancers. That's the exciting part of this paper.

PALCA: Because Diaz believes it may be possible to design drugs that will prevent these genes from causing chromosomal instability. Doing that might be extremely useful in keeping cancers in check.

Joe Palca, NPR News, Washington.

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