Radiologists interpreting breast MRI studies should consider patient age and clinical indication when reading the scans, due to higher rates of malignancy associated with these factors, according to a study published in the October issue of Academic Radiology.
Dr. Robert Gutierrez and colleagues at the University of Washington in Seattle confirmed that older women and those receiving breast MRI studies for diagnostic applications rather than screening had higher rates of malignancy. Physicians reading these types of studies should take this information into account when analyzing suspicious lesions (Academic Radiology, Vol. 16:10, pp. 1281-1285).
"Prior studies have focused predominately on the risk of malignancy related to MRI lesion morphology and lesion kinetics," Gutierrez and colleagues wrote. "The focus of this study was to better define the role that patient characteristics play in determining risk of malignancy in nonpalpable, mammographically occult, MRI-detected suspicious lesions."
The team performed an audit of all consecutive breast MRI exams conducted at the University of Washington Medical Center between January 2003 and November 2006. The study included a total of 2,569 exams, which were performed on a Signa LX 1.5-tesla scanner (GE Healthcare, Chalfont St. Giles, U.K.). All lesions detected in the exams fell into the BI-RADS 4 or 5 categories, and all were subject to ultrasound-guided needle biopsy, MRI-guided vacuum-assisted biopsy, or surgical excisional biopsy.
Gutierrez's group identified 405 suspicious lesions in 299 women (mean age, 51 years) who had subsequent needle or excisional biopsy. Of the suspicious lesions, 151 were malignant (37%) and 254 were benign (63%). Of the malignancies, 45 were ductal carcinoma in situ, 75 were invasive ductal carcinoma, 25 were invasive lobular carcinoma, and six were "other."
A total of 196 lesions (48%) were in patients younger than 50, and 209 (52%) were in patients 50 or older. Most of the lesions, or 76.3%, were in patients who had undergone breast MRI for an indication of newly diagnosed cancer and represented additional, unsuspected lesions. The remaining 23.7% were in patients who had breast MRI for high-risk screening.
Clinical indication and patient age were strong predictive factors for malignancy. Lesions found after cancer had been diagnosed were more likely to be malignant than those in patients who had received a breast MRI for high-risk screening (42.1% compared to 21.9%), and lesions in patients 50 or older were more likely to be malignant than those in patients younger than 50 (44% compared to 30.1%).
The results weren't surprising, Gutierrez told AuntMinnie.com, but they are key, nonetheless, to refining the use of breast MRI.
"People order breast MRIs for many reasons, and other studies haven't separated the various patient population characteristics," he said. "So patients who receive MR for high-risk screening are mixed with those who receive it for an evaluation of extended disease. We wanted to show that it's important to handle diagnosis and screening breast MRI separately, just as is done in mammography."
With the goal of improving overall diagnostic accuracy of breast MRI, the study data support including patient age and clinical indication when determining the risk of malignancy in lesions detected initially on breast MRI, Gutierrez and colleagues wrote.
"We hope our data will help individual radiologists sitting down to read a breast MR find ways to better determine a lesion's level of suspicion," Gutierrez said.
By Kate Madden Yee
AuntMinnie.com staff writer
September 18, 2009
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