Will Cancer Spread? Sound out NMR
Raloff, Janet, Science News
Will cancer spread? Sound out NMR
A Canadian scientist has adapted a standard chemical assaying technique to identify whether solid cancerous tumors have the ability to spawn secondary growths, called metastases. In a recenlty completed study of 200 human adenocarcinomas -- 70 percent colon cancers, 30 percent breast tumors -- Ian C.P. Smith correctly diagnosed 27 cancers as having apparently "no metastatic potential." It is significant, he notes, that none of his diagnoses falsely predicted that a cancer would not spread.
If such metastatic diagnoses prove as reliable as the preliminary studies suggest, they might one day offer physicians the option of prescribing postsurgical radiation or chemotherapy directed only at the primary tumor, says Smith, director of the Canadian National Research Council's Division of Biological Sciences in Ottawa. Thus some patients might qualify for a more benign therapy than the treatment used to tackle unseen metastases today, he says.
Over the past decade, most major hospitals have adopted nuclear magnetic resonance (NMR) imaging, also known as magnetic resonance imaging, as a noninvasive tool for peering into the body. But chemists have used NMR spectroscopy -- which can identify and quantify chemical species within complex samples -- for at least 30 years. And a technique based on this spectroscopic side of the technology lies behind Smith's work, which he described in Toronto last week at the Third Chemical Congress of North America.
Smith irradiated samples (from tumors removed during surgery) with radiofrequency radiation. This energy "excited" nuclei of certain atoms in the cancerous tissue to a higher energy. When the NMR beam shut off, the atoms "relaxed" to their initial energy state. Each chemical constituent has a unique relaxation profile, or signature, that allows its identification.
Smith focused on relaxation rates for the methylene (CH. …