N E W O R L E A N S,
May 23 — 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
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.
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
Cell ActivityA 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
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.
that expectations of cure in this type of therapy is much less than 20
percent,” McManus said.
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
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
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
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
He said up to half of all patients have a
disease that, after surgery, is seen to be more serious than first
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
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
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.
looked at the number of blood vessels in each tumor,” Cox said. Tumors
grow blood vessels to feed themselves, a process known as
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
“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
If a patient’s tumor had none
of these factors, the chance of death was only 36
“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