A U.S. study shows doctors change the way they treat 60% of advanced breast cancer patients after viewing results from a PET scan, a diagnostic test widely used in the United States but almost unavailable in Canada.

Physicians switched treatments because the PET results were more accurate in determining the spread of breast cancer than traditional imaging technologies such as CAT scans or MRIs, said Johannes Czernin, lead author of the study and director of the nuclear medicine clinic at the University of California at Los Angeles.

For example, a patient could be scheduled for surgery after a dark mass appeared on a CAT image, but a PET scan might reveal the mass on the breast is benign and the surgery not necessary.

"If you can limit treatment to the most useful things and not do things like unnecessary surgeries that will adversely affect the quality of life of these patients, it's really a great step forward," said Dr. Czernin.

Canadian doctors are hoping the study, published in today's Journal of Nuclear Medicine, will bolster their pleas for the technology to be made available here.

"For patients with breast cancer, there really is the opportunity of being able to say, 'Look, we know your cancer treatment now isn't working -- you may think it is working -- but now we can tell you it's not on the basis on the PET scan. We want to change it to something that will work," said Dr. Sandy McEwan, an oncologist at the Cross Cancer Institute in Edmonton.

"Because there are so many therapies for breast cancer, it is very important we know exactly where we are in managing patients. What is the cancer? Where is it? How is it responding? Because if we get the beginning of a failure of response we can change to treatments that we know work very well."

Only two PET scanners are publicly available to cancer patients in Canada. There are about 250 in the United States, where much of the research on the technology occurs.

Positron Emission Tomography uses radioactive pharmaceuticals to detect cancer tumours and has not been found to have side effects.

The scans, which view molecular changes in cells, are commonly used in the United States to diagnose and examine patients with lung cancer, colon cancers, cancers in the head and neck, and lymphoma and melanoma.

The UCLA study of 50 patients is among the first to examine if PET scans are useful for women with advanced breast cancer.

In June, a U.S. Medicare advisory committee agreed to reimburse patients with recurrent breast cancer who undergo the scan. Other cancers are already covered.

Dr. Czernin said he is surprised Canada has only two PET scanners. He noted that Japan has 48 scanners while Germany has 45. Austria has at least seven and Belgium has close to 20.

"I wouldn't work in that environment," he said, referring to the Canadian situation.

A third Canadian PET scanner, located in Edmonton, was purchased this summer with research funds. However, there is only enough money to operate the machine for cancer patients a few hours a week, said Dr. McEwan.

One of Canada's two full-time PET scanners operates at Sherbrooke University Hospital, where François Bénard examines about 25 to 30 patients a week using the scanner the Quebec hospital purchased in 1998. About 10% of the patients have breast cancer.

"It definitely changes the way we manage patients, avoiding lots of unnecessary surgery. It helps predict disease when other tests are negative," said Dr. Bénard, a nuclear medicine physician.

"It saves a lot of, I would say, pain and suffering for cancer patients."

But at a cost of between $1.5-million and $3-million per machine, plus hundreds of thousands of dollars to maintain them each year, provincial governments have been slow to embrace the technology.

A private company is taking advantage of the lack of PET scanners in the public health care system and plans to offer the diagnostic test for $2,500 at clinics in three provinces within a year.

Breast cancer is the most common cancer among Canadian women, striking about one in nine. Last year, an estimated 19,200 Canadian women were diagnosed with the disease and 5,500 died.