PET/MRI May Help Detect Some Metastases from Breast Cancer

Combined PET/MRI may help detect some but not all metastases from breast cancer.

Imaging with PET and MRI for patients with breast cancer may help identify liver and bone metastases, but not pulmonary metastases, according to a study published in Radiology.

Researchers from the New York University School of Medicine performed a prospective study to compare fluorine 18 (18F) FDG combined PET and MR imaging with 18F FDG combined PET and CT in terms of organ-specific metastatic lesion detection and radiation dose in patients with breast cancer.

The study included 51 patients with breast cancer (50 women). Their mean age was 56 and the one man in the study was aged 70. All had completed PET/MR imaging with diffusion-weighted and contrast material–enhanced sequences after unenhanced PET/CT. Two independent readers for each modality recorded site and number of lesions. Imaging and clinical follow-up, with consensus in two cases, served as the reference standard.

The results showed 242 distant metastatic lesions in 30 patients, 18 breast cancers in 17 patients, and 19 positive axillary nodes in eight patients. There was no evidence of primary or metastatic disease in 13 patients. In all, PET/MRI showed greater sensitivity than PET/CT in detecting distant metastases in the liver.

According to the researchers, the PET/MR imaging showed increased sensitivity for liver metastases, at 100% for reader 1 and 80% for reader 2, compared with 75% for reader 3 and 70% for reader 4. With bone metastases, sensitivity was 98% for reader 1 and 95% for reader 2, compared with 99% for reader 3 and 87% for reader 4. Brain metastases was found in 10% of the patients.

PET/CT trended toward increased sensitivity for lung metastases at 87%for reader 1 and 74% for reader 2 compared with 100% for reader 3 and 96% for reader 4. Dose reduction averaged 50%.

The researchers concluded that PET/MR imaging may yield better sensitivity for liver and possibly bone metastases among patients with breast cancer, but not for pulmonary metastases, as compared with that attained with PET/CT, at about half the radiation dose.