TUESDAY, April 9, 2002 (HealthDayNews) -- PET scans can avoid unnecessary surgery for people with suspected recurrence of colorectal cancer, and can help doctors make better treatment decisions.
A new Australian study found that more than 60 percent of surgeries planned for 43 people with suspected recurrence of colorectal cancer were deemed unnecessary after they were given PET (positron-emission tomography) scans. The research appears in the April issue of The Journal of Nuclear Medicine.
"I must say that we were quite surprised at the degree of impact we had," says lead author Dr. Rodney J. Hicks, director of nuclear medicine and PET at The Peter MacCallum Cancer Institute at the University of Melbourne.
Positron-emission tomography uses radioactive positrons and provides color-coded images of the body that alert doctors to changes in the body's metabolism and chemical activity.
The value of PET scans went beyond the dramatic impact on surgeries. A third of the people in the study had their treatment drastically changed because of the scans, Hicks adds.
For example, some had their treatment altered from attempts to cure the disease to simply managing it once the scan had shown there was no hope of recovery, Hicks says. Other patients were switched from one form of treatment -- chemotherapy, radiotherapy or surgery -- to another.
In some cases, people were given more intense radiation or more extensive surgery, according to Hicks. The PET scans offered reassurance to five people who had suspicious findings on conventional imaging. Their scans were normal, and follow-ups showed no recurrence of the cancer.
The study examined the PET scans and treatment of 96 people with suspected recurrence of colorectal cancer whose doctors had proposed treatments before the PET scans were done. It also included six people whose doctors wanted to wait for PET scan results before deciding the best course of treatment.
"The major advantage in the abdomen is that it offers much greater contrast between diseased tissues and normal tissues," compared to other imaging technologies such as CT scans, ultrasounds or magnetic resonance imaging (MRIs), Hicks says. To top it off, PET scans have very few false positives, results that can been misleading on first readings.
There are limitations. Pet scans can't detect tiny clusters of diseased cells, but that's the case with all imaging techniques, Hicks says.
An American expert says it's common to use PET scans to investigate suspected recurrence of colorectal cancer.
"We have been doing PET scans for that for some time, but this gives us increasing evidence that in fact, what we think we're doing right is indeed correct," says Dr. Harvey Ziessman, director of nuclear medicine and professor of radiology at Georgetown University Hospital.
"It's not perfect, and no one would say you should use it alone. Everybody would agree that CT scanning is still required. PET can't see very small lesions, that is, tumors less than a centimeter in size," Ziessman says.
What To Do
Colorectal cancer is the second most deadly cancer in the United States, says the U.S. National Cancer Institute.
The American Cancer Society estimates there will be 148,300 new colorectal cancer cases, and 56,600 deaths from colorectal cancer in 2002.
Your lifetime risk of developing colorectal cancer is nearly 6 percent. More than 90 percent of cases occur after age 50.
For more information, go to the National Cancer Institute or the American Cancer Society.
