After Colorectal Cancer Spreads, Additional Imaging Adds Little Benefit

For patients whose colorectal cancer has spread to the liver, and confirmed by computed tomography (CT), further imaging scans before surgery added little benefit when compared to patients who did not undergo further imaging.

Principal investigators, Carol-Anne Moulton, MB, BS, and Steven Gallinger, MD, of the Ontario Clinical Oncology Group (OCOG) randomly assigned patients with colorectal cancer with surgically-removable metastases based on CT scans to either PET-CT (positron emission tomography) or no further imaging (control) to determine the effect on the surgical management of these patients.

"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 Steven Gallinger, MD, professor of Surgery at the University of Toronto in release.

Traditionally, patients with colorectal cancer undergo surgery to remove the cancer, but approximately 50% of patients experience liver metastases. Some patients with liver metastases are candidates for liver surgery, which can lead to long-term survival. However, unidentified metastases outside the liver at the time of surgery can render the operation non-curative and thus futile.

Therefore, long-term survival following surgical removal of colorectal cancer liver metastases is relatively low, about 50 percent. The usual practice is to perform a CT scan before surgery to determine the extent of the cancer. PET scans combined with computed tomography (PET-CT) could help avoid non-curative surgery by identifying patients with hidden metastases.

"There has been a tendency for expensive imaging tests to be adopted in practice without rigorous evaluation,” said Mark Levine, MD, a co-author. Trials such as this one play “an important role to provide the evidence that ultimately helps to inform and change health policy," continued Levine in a release, who is also Professor and Chair of the department of Oncology at McMaster University.

The study, conducted between 2005 and 2013, enrolled 404 patients and involved 21 surgeons at nine hospitals in Ontario. Researchers report that the median follow-up was three years. They found no significant difference in survival or disease-free survival between patients in the PET-CT group versus the control group.

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% of cases; only 2.7% avoided non-curative liver surgery. Overall, liver resection was performed on 91% of patients in the PET-CT group and on 92% of the control group.

The findings are published in the May 14 issue of the Journal of the American Medical Association (JAMA).