Report from ISMRM: MRS staves off unnecessary breast biopsies

May 10, 2005

Single-voxel proton MR spectroscopy could save many women from the pain and expense of unnecessary breast biopsy.

Single-voxel proton MR spectroscopy could save many women from the pain and expense of unnecessary breast biopsy.

Several studies have shown that MRS could boost the limited specificity of x-ray mammography and contrast-enhanced MR imaging, according to Dr. Wei Huang, a radiology researcher at Memorial Sloan-Kettering Cancer Center. The studies posted specificities of 82% to 100% for the ability of MRS to differentiate between benign and malignant breast lesions.

"There is definitely a need to improve specificity in breast cancer detection," he said

The added diagnostic power of MRS could help physicians avoid prescribing unnecessary breast biopsies. That capability was demonstrated in a study of 57 women who underwent MRS after a suspicious lesion was identified with MR mammography. Huang presented his results Monday at the International Society for Magnetic Resonance in Medicine annual meeting in Miami.

Huang and colleagues performed MRS along with contrast-enhanced MR-guided needle localization or biopsy within a week of initial diagnosis. The cases involved lesions of at least 1 cm in diameter and a BI-RADS score of 4 or 5, signifying a high probability of malignancy.

MRS was performed on a 1.5T scanner equipped with a body coil for radiofrequency transmission and a four to eight-element phased-array coil as receiver. An MRS voxel of 1.6 to 11.2 cc was located in the contrast-enhanced lesion, and data were acquired using a standard PRESS sequence with a TE and TR of 135 msec and 2000 msec, respectively. Scan time was less than 10 minutes.

Lesions were classified as benign or malignant on the basis of their peak choline ratios. Abnormalities with apparent choline peak signal-to-noise ratios of greater than 2 were called malignant. Lower peaks indicated an absence of cancer, Huang said.

The MRS test for peak choline produced no false negatives, three false positives, and true negatives for all 26 lesions that were confirmed as benign with biopsy. That experience translated statistically into a sensitivity of 100% and specificity of 88%. Positive and negative predictive values were 91% and 100%, respectively. The accuracy rate was 95%.

The addition of MRS would have raised the positive predictive value of the entire imaging regime by 47%, according to Huang. More important, it would have spared 23 patients in the study from unnecessary biopsy, and no cancers would have been missed.

The MSKCC group plans to repeat the protocol on a 3T scanner to measure the value of MRS for eliminating unnecessary biopsy ordered for smaller lesions.

For more information from the Diagnostic Imaging archives:

3T broadens scope of MR spectroscopy

MR spectroscopy adds specificity to breast MR