Proton MR Spectroscopy with Choline Peak as Malignancy Marker Improves Positive Predictive Value for Breast Cancer Diagnosis: Preliminary Study

Abstract

To prospectively evaluate the diagnostic performance of magnetic resonance (MR) spectroscopy in patients with suspicious lesions or biopsy-proved cancers at MR imaging by using histologic findings as the reference standard. After institutional review board approval and informed consent were obtained for this HIPAA-compliant study, breast MR spectroscopy was performed in patients with suspicious or biopsy-proved malignant lesions measuring 1 cm or larger at MR imaging. Single-voxel MR spectroscopy data were collected from a single rectangular volume of interest that encompassed the lesion. MR spectroscopy findings were defined as positive if the signal-to-noise ratio of the choline resonance peak was greater than or equal to 2 and as negative in all other cases. MR spectroscopy findings were then compared with histologic findings. A total of 56 patients (age range, 20-77 years) with 57 lesions were imaged. The median lesion size at MR imaging was 2.3 cm (range, 1-15 cm). Histologically, 31 (54%) of 57 lesions were malignant, and 26 (46%) were benign. A choline peak was present in 34 of 57 lesions (including all cancers) and in three of 26 benign lesions, giving MR spectroscopy a sensitivity of 100% and a specificity of 88%. In 40 lesions of unknown histologic type, the use of MR spectroscopy as an adjunct to MR imaging would have significantly (P<.01) increased the positive predictive value of biopsy from 35% to 82%. If biopsy had been performed only on those lesions with a choline peak at MR spectroscopy, biopsy may have been spared in 23 (58%) of 40 lesions, and none of the cancers would have been missed. Proton MR spectroscopy was successfully incorporated into breast MR imaging studies for lesions measuring 1 cm or larger. This technique may be useful in reducing the number of lesions detected at MR imaging that require biopsy.