Tracking the course of cancer treatment with PET scans

Caren B. Les

Patients with colorectal cancer may benefit from better treatment planning if they receive positron emission tomography (PET) scans. Researchers conducted a study at four PET centers in Australia to examine the impact of the imaging technique on changing the care of patients with proven or suspected recurrence and to assess the impact of the change on disease-free survival. The scans led to changes in the disease management of more than half of the patients who participated in the study.

Shown is an image of a 2-[18F] fluoro-2-deoxy-D-glucose PET/CT scan in a patient with a potentially resectable liver lesion (solid arrow) that was detected on pre-PET imaging. PET revealed additional lesions in the liver, nodal involvement, and a mesenteric lesion (open arrow). As a result of the PET scan, surgery on the liver was avoided, and more appropriate and effective treatment was provided. Photo courtesy of Dr. Andrew M. Scott.

Colorectal cancer is the fourth most common cancer in the US, according to the National Cancer Institute in Bethesda, Md. It is estimated that nearly 50,000 Americans will die from the disease in 2008.

The study, led by Dr. Andrew M. Scott, director of the Centre for PET and the Ludwig Institute for Cancer Research, at Austin Hospital in Melbourne, Australia, involved 191 patients who underwent PET scanning. Prior to the scanning, they were divided into two groups: Group A patients showed symptoms and had residual structural lesions that were suspicious for malignant recurrence after initial therapy, while group B patients were known to have pulmonary or hepatic metastases that possibly could be treated through surgery.

Referring clinicians were required to document a management plan for a patient based on conventional imaging, such as computed tomography (CT), before they received the results of the PET scans. Following release of the scans, they had to record a second plan, including any changes as a result of the scans. Researchers followed the actual management plans and clinical outcomes of the participants for 12 months.

The investigators found that PET detected additional disease in 48.4 percent of the patients in group A and in 43.9 percent of those in group B. The PET results prompted the referring clinicians to change the treatment plans in 65.6 percent of the group A patients and in 49 percent of the group B participants. The plans were carried out in 96 percent of the patients.

The follow-up data from group A indicated progression of the disease in 60.5 percent of the patients with additional lesions identified by PET, compared with conventional imaging, and in 39.2 percent of the patients with no additional disease revealed by PET. In group B, disease progression was identified in 65.9 percent of patients with additional lesions detected by PET and in 39.2 percent of patients with no additional lesions detected by PET.

The PET scans enabled physicians to determine with greater accuracy whether patients in either group could benefit from further treatment, such as surgery, or if palliative care was indicated.

Journal of Nuclear Medicine, September 2008, pp. 1451-1457.