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High-Tech PET Scan 'Sees' Cancer Better

By Elizabeth Tracey , MS
WebMD Health News

May 24, 2000 (New Orleans) -- Use of a radioactive high-tech scan called PET may help patients with some kinds of cancer avoid unnecessary surgeries that do not cure the disease. Two new studies presented here at a meeting of the world's leading cancer researchers and doctors show that this new test, though expensive, is much better at seeing lung cancer than the older CAT scan. Researchers expect that PET will be as helpful for other cancers as well.

PET scans differ from conventional CAT because this newer test is better able to detect much smaller, microscopic amounts of cancer cells that have been left over after treatment and to verify that a suspicious mass is truly cancer. CAT, on the other hand, is only able to detect larger masses, and only a surgical procedure, or biopsy, can verify that the CAT-detected mass is cancer.

A PET scan alone can verify that even small masses are cancerous because the technique uses a type of sugar, or glucose, that glows. Cancer cells ingest larger amounts of glucose than normal cells, so they glow "hotter" than normal cells. So while CAT can identify suspicious masses based on their size, PET scans can identify masses that are cancerous based on their behavior.

Researchers from the Peter MacCallum Cancer Institute in East Melbourne, Australia, used PET to verify whether the lung cancer patients in their study had successfully responded to their treatment with surgery, chemotherapy, and/or radiation therapy. All patients had non-small cell lung cancer, the most common form of lung cancer. Compared with CAT, PET was better at predicting which patients would survive and in identifying which patients would need more aggressive treatment to combat their disease.

Doctors usually treat non-small cell lung cancer with surgery only when they think they can remove all of the cancer -- meaning when they don't think that the cancer has spread, or metastasized, outside the lung. Doing surgery once the cancer has metastasized does not benefit the patient, according to Michael MacManus, MD, a research involved in the Australian study.

Another study by researchers in The Netherlands tested how well PET scanning is at finding lung cancer that has spread before the patients have surgery. "We know that surgery is futile in about one in five patients with non-small cell lung cancer," says Harm van Tinteren of the Comprehensive Cancer Center Amsterdam in The Netherlands. "We used PET to determine whether we could predict which patients would not benefit from surgery." Preliminary results show that PET successfully reduces the number of futile surgeries for lung cancer by 50%, he says.

Cancer researchers and doctors are coming to a better understanding of how lung cancer develops through the use of techniques such as PET, comments cancer expert Frank Haluska, MD, PhD. "Ultimately, this will allow us to direct our therapies or use the most appropriate therapies, whether those are surgery, chemotherapy, or more novel approaches. I think patients who will not benefit from surgery will be enthusiastic about avoiding it when it has been demonstrated that there is no clear benefit."

Haluska continues, "What this really allows us to do is obtain information we have always obtained by other means, especially surgical means, in a minimally invasive and more accurate way."

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