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Combined Imaging Improves Colorectal Cancer Diagnosis

Computer tomography and positron emission tomography at once benefits patients, study finds

TUESDAY, Dec. 5, 2006 (HealthDay News) -- The combination of two imaging techniques -- positron emission tomography and computed tomography -- provides quicker and more precise information to guide the treatment of colorectal cancer, German doctors report.

Exact and complete information on the "stage" -- or severity -- of a tumor is critical, said the physicians at University Hospital Essen. Typically, getting that information requires a series of imaging sessions, each one supplying a segment of the picture.

The German study compared the use of newly available positron emission tomography (PET)/computed tomography (CT) devices to older, conventional techniques for diagnosis of 47 patients with colorectal cancer.

CT alone correctly diagnosed 52 percent of the cancers, the report said. CT followed by PET was accurate in 64 percent of the cases. But the PET/CT combination was 22 percent more accurate in defining the exact stage of the tumor.

Most important, the PET/CT combination was most successful in designing treatment for individual patients, the report said. It changed therapy management in four of the patients.

"Based on the results of our study, we have integrated PET/CT colonography in our daily clinical routine," said Dr. Gerald Antoch, associate professor of radiology at Essen, and lead author of the report.

But Antoch cautioned that the study "must be considered preliminary," and "further studies are required to confirm these results in a larger patient cohort."

Such a study will be done at Essen, Antoch said.

"Whole-body PET/CT colonography as an all-in-one staging modality seems feasible to provide an alternative to the multimodality, multi-step staging in patients with colorectal cancer," the report stated. "It is less time-consuming than a conventional multi-step approach... Thus, it represents a psychological and physical advantage when considering the burden to the patient."

The study is published in the Dec. 6 issue of the Journal of the American Medical Association.

The introduction of machines that combine PET and CT scans has been a major advantage, said Dr. Christiaan Schiepers, professor of molecular and medical pharmacology at the University of California, Los Angeles, Medical Center.

"In the old days, we had CT separate and PET separate," he said. "When you combine the two in one machine, you have the images aligned. PET gives you metabolic information, CT tells you structural image -- what is muscle, fat or tumor."

What the German physicians appear to have done is to "develop a new protocol that allows them to do everything in one session," Schiepers said. "There already are ways to enhance images and improve contrast and other things."

Determining the exact stage of a tumor can make a world of difference to doctor and patient, Schiepers said. "It tells you whether you have to be very aggressive or can be more accommodative," he said.

Other than skin cancer, colorectal cancer is the third most common cancer in the United States. The American Cancer Society estimates there will be about 106,680 new cases of colon cancer and 41,930 new cases of rectal cancer this year. Combined, they will cause about 55,170 deaths.

More information

To learn more about colorectal cancer, visit the National Library of Medicine.

SOURCES: Gerald Antoch, M.D., associate professor of radiology, University Hospital Essen, Germany; Christiaan Schiepers, M.D., professor of molecular and medical pharmacology, University of California, Los Angeles, Medical Center; Dec. 6, 2006, Journal of the American Medical Association
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