PET/CT improves detection of metastatic colorectal cancer

Simultaneous imaging with positron emission tomography (PET) and computed tomography (CT) is more sensitive than contrast-enhanced CT (ceCT) alone in the evaluation of patients for metastatic colorectal cancer, physicians in Switzerland report.

In fact, a change of therapy results for approximately one in five patients when PET/CT is used instead of ceCT, Dr. Pierre-Alain Clavien and his team at University Hospital in Zurich report in the December Annals of Surgery.As they point out, the tumor load is often underestimated in patients with metastatic colorectal cancer. The researchers therefore devised ‘a new technique combining the same imaging session data of a full-ring PET-scanner with a multi-detector row helical CT.’ In the procedure ‘PET-positive lesions are projected directly into the CT scan to obtain simultaneous functional and anatomic information.’They prospectively assessed the use of ceCT and this new PET/CT technique in 76 colorectal cancer patients evaluated for resection of liver metastases. The findings were verified based on intraoperative findings and follow-up with serial ceCT.The authors observed no difference between the two modalities regarding primary intrahepatic metastasesHowever, PET/CT identified local recurrence at the site of the primary tumor in 15 patients, versus the 9 identified by ceCT (sensitivity 93% versus 53%).Extrahepatic metastases were identified in 34 patients with PET/CT and 24 with ceCT (sensitivity 89% versus 64%).Overall, PET/CT changed the therapeutic strategy in 16 patients (21%). Ten patients considered resectable by ceCT were found to have extensive extrahepatic disease, representing a contraindication for surgery. Six patients underwent liver resection and removal of the peri-portal nodes based on PET/CT findings that were missed by ceCT.Because intrahepatic vascular structures are poorly delineated with PET/CT, the research team now uses intravenous contrast when evaluating these patients.’This may obviate the need for additional ceCT or magnetic resonance imaging, or perhaps colonoscopy. Such a strategy would be attractive, enabling a one-step diagnostic procedure,’ they conclude.(Source: Ann Surg 2004;240:1027-1036: Reuters Health: Oncolink: December 2004.)