image of Dr. Carol-Anne Moulton
Dr. Carol-Anne Moulton, Co-Principal Investigator of the clinical trial, is a surgeon in the Hepatobiliary/Pancreatic Surgical Oncology Program at the University Health Network. (Photo: UHN)​

Among patients with colorectal cancer which has spread to the liver, further imaging using positron emission tomography (PET) scans before surgery did not significantly change the surgical treatment of the cancer compared with no further imaging, according to a study led by Toronto General Hospital (TGH) surgeons.

Principal Investigators, Dr. Carol-Anne Moulton and Dr. Steven Gallinger, and their Ontario colleagues, randomly assigned patients with colorectal cancer with surgically-removable metastases based on computerized tomography (CT) scans to either PET-CT or no further imaging (control) to determine the effect on the surgical management of these patients.

The usual practice is to perform a CT scan before surgery to determine the extent of the cancer. Positron emission tomography combined with computed tomography (PET-CT) could help avoid non-curative surgery by identifying patients with hidden metastases.

The researchers found no significant difference in survival or disease-free survival between patients in the PET-CT group versus the control group. The findings are published in the May 14 issue of the Journal of the American Medical Association (JAMA).

"To our knowledge, our study is the largest, based on high-quality imaging and reading of scans, to understand the role of PET-CT in selecting the best colorectal cancer candidates whose cancer has spread to the liver for surgery. We did not anticipate that PET-CT would have such a small impact on hepatic surgery in our patients," said Dr. Steven Gallinger, Co-Principal Investigator of the clinical trial, Head, Hepatobiliary/Pancreatic Surgical Oncology Program, University Health Network and Mount Sinai Hospital, and Professor of Surgery, University of Toronto.

The study, conducted between 2005 and 2013, enrolled 404 patients and involved 21 surgeons at nine hospitals in Ontario. The median follow-up was three years.

In Canada, cancer of the colon or rectum (colorectal) is a leading cause of cancer death. Patients with colorectal cancer undergo surgery to remove the cancer, but approximately 50 percent of patients develop spread of the cancer to the liver (liver metastases).

Some patients with liver metastases are candidates for liver surgery in order to remove the cancer which can lead to long term survival. However, "occult" or "small hidden" tumours elsewhere in the liver or outside of it at the time of surgery can make the operation non-curative and unnecessary. Long-term survival following surgical removal of colorectal cancer liver metastases is relatively low, about 50 percent.

New radiology techniques are being developed all the time to try and find these hidden tumours. One of these is PET scanning and many PET scans have been performed for patients throughout the world for cancer detection. However, new imaging techniques, such as PET scans are expensive and it is important that we understand the place for these tests in helping patients, especially when health care costs are increasing.   

"The decision to adopt a new medical practice or additional test should be informed by rigorous evidence on its effectiveness, benefits, along with any possible harmful effects. In a health care environment where patients want and need to have the best information to make informed decisions, research on the effectiveness of a specific treatment or test will become increasingly important to help patients and their physicians understand all the facts,"  said Dr. Carol-Anne Moulton, Co-Principal Investigator of the clinical trial, surgeon in the Hepatobiliary/Pancreatic Surgical Oncology Program, University Health Network, and Associate Professor of Surgery, University of Toronto.

Of the 263 patients who received PET-CT scans, 159 had no new information on PET-CT; 49 had new abnormal or suspicious lesions on PET-CT and in 62 the PET-CT did not identify the lesion in the liver identified on the baseline CT. Change in management (canceled, more extensive liver surgery, or surgery performed on additional organs) as a result of the PET-CT findings occurred in 8.7 percent of cases; only 2.7 percent avoided non-curative liver surgery. Overall, liver resection was performed on 91 percent of patients in the PET-CT group and on 92 percent of the control group.​

The PET-CAM trial is one of seven trials that OCOG has performed in recent years as part of the Provincial PET in Oncology Program. The results of these studies have informed policy for the Ontario Ministry of Health & Long Term Care on whether to fund PET for a specific indication. OCOG is the world leader in conducting trials to evaluate the utility of PET in oncology.

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