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Conquer Cancer Health News

Accurate Diagnosis Two New Tests Predict Cancer Outcome PET Scan denoting a patient whose tumor was eradicated. M. McManus (HO)

Maggie Fox

NEW ORLEANS - Two new approaches to diagnosing cancer could save many patients from needless surgery and better predict whether patients are doomed to die of the disease, doctors said today.

One approach uses positron emission tomography (PET) scans to see if a tumor is still alive and spreading, while another looks for the telltale proteins produced by the most dangerous kinds of tumors.

Currently, doctors use X-rays and a souped-up X-ray called a computed tomography, or CT, scan to diagnose tumors.

"CT gives a very good description of the shape and structure of masses such as tumors, but it is no good at telling what is going on in these structures," Dr. Michael McManus of the Peter MacCallum Cancer Institute in East Melbourne, Australia, told reporters.

"PET can see inside the mass."

Scanning Cell Activity

A PET scan looks at actual cell activity. Tumors use more glucose than normal tissue, so radioactive glucose can be given to a patient and then tracked using PET.

Two teams of researchers told a meeting of the American Society of Clinical Oncology (ASCO) in New Orleans about using PET scans to help lung cancer patients.

McManus used PET scans on 56 lung cancer patients whose tumors could not be removed surgically. They get chemotherapy or radiation, but the treatment does not usually work well.

"We know that expectations of cure in this type of therapy is much less than 20 percent," McManus said.

PET Scan Finds Sneaky Tumors

When patients were examined after treatment, many seemed to have been "cured" according to a CT scan, but PET scans showed their tumors were still active.

And in some people who seemed to have a tumor when X-rayed using CT scans, PET showed the mass was dead tissue. PET scans also showed when cancer cells invaded a lymph node that appeared normal on a CT scan because it had not yet begun to grow or change shape.

Patients whose tumors looked active on the PET scans had four times the risk of dying, and patients whose PET scans showed the cancer was still progressing had a 45 times greater risk of dying, McManus reported.

"It seems that most of those patients are doomed to die of their disease," he said.

Dr. Harm van Tinteren of the Comprehensive Cancer Centre in Amsterdam said PET scans might be used to help doctors tell which patients might be helped by surgery or other treatments, and which ones have hopeless cancers and might be best served by treatment that eases their pain while they die.

He said up to half of all patients have a disease that, after surgery, is seen to be more serious than first diagnosed.

His team studied 96 lung cancer patients who received standard lab tests and 92 patients who got standard tests plus a PET scan.

"PET more accurately shows the extent and stage of disease," Van Tinteren said.

McManus said the PET scans also worked for other cancers such as melanoma, a deadly form of skin cancer, head and neck cancer and colon cancer.

Predicting the Dangers

A third team of researchers took another approach to predicting which cancers are the most dangerous.

Dr. Giles Cox of the Leicester Royal Infirmary in Britain examined tumors taken from 168 patients and looked for proteins either associated with dangerous tumors, or known to be involved in tumor growth and spread.

"We looked at the number of blood vessels in each tumor," Cox said. Tumors grow blood vessels to feed themselves, a process known as angiogenesis.

They also looked at the levels of enzymes known as matrix metalloproteinases (MMPs), which are involved in breaking down and rebuilding tissue so that tumors can spread, and for a receptor, a kind of cellular doorway, called epidermal growth factor receptor (EGFR).

"If the tumor had a high number of blood vessels, MMP-2, MMP-9 and growth factor receptors, then there was an 84 percent chance of cancer mortality in these patients," Cox told reporters.

If a patient's tumor had none of these factors, the chance of death was only 36 percent.

"We can identify those at high risk of recurrence," Cox said. "The prospect of treatment tailored to the individual patient and to the individual tumor characteristics, we believe, is possible."

Drugs are being developed that specifically interfere with MMPs and with various tumor growth factors.

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