PET/MRI bests other modalities in imaging liver metastases related to colorectal cancer

Combined PET/MRI outperforms multidetector CT and PET alone in evaluating colorectal cancer liver metastases (CRLMs), according to study results published online April 19 in the journal Radiology.

More than half of patients with colorectal cancer also experience distant metastasis of the liver, the treatment for which is hepatic resection. Because of late detection associated with the condition, only about one-third of patients with CRLMs are eligible for the risky procedure, which has only a 25-58 percent survival rate.

With advancements in chemotherapy and improved surgical capabilities, some patients who were not previously eligible for the procedure may have hope, as long as the extent of the disease can be imaged accurately, said Dong Ho Lee, MD, of Seoul National University Hospital, South Korea, and his co-authors.

“Until now, multidetector CT has been the most widely used modality in the diagnosis and follow-up of CRLMs,” they wrote. “Recently, a fully integrated PET/MR imaging system that can yield complementary anatomic and metabolic information was introduced to oncologic imaging … several recent studies have already shown the prognostic potential of this PET/MR imaging system in patients with head and neck cancers and in those with bone tumors.”

Lee and his team set out to compare the diagnostic performance of PET/MRI to that of multidetector CT and PET in the detection of liver metastases and to assess prognostic value in patients with CRLMs.

To do so, they conducted a retrospective study of 55 patients who underwent multidetector CT, whole-body PET, MR imaging with a liver-specific contrast agent and PET/MRI between January 2013 and June 2014, 18 of whom also underwent neoadjuvant chemotherapy.

Their results showed that PET/MR imaging performed better than both multidetector CT and PET in the detection of CRLMs, though no significant difference was found between PET/MRI and PET/MRI with a liver-specific contrast agent. They also discovered a significant difference in one-year recurrence-free survival rates between patient with isometabolic CRLMs (80 percent) hypermetabolic CRLMs (14 percent).

“PET/MR imaging can yield significantly higher diagnostic performance in the detection of CRLMs when compared with the performance of multidetector CT or PET,” the researchers concluded. “In addition, the degree of fluorodeoxyglucose uptake after NAC may have the potential to yield prognostic information for recurrence-free survival after hepatic resection.”