Added functional MR sequence helps distinguish recurrent sarcoma from scarring

The addition of functional MR sequences to a routine MRI protocol, especially dynamic contrast-enhanced MRI, offer a specificity of more than 95 percent for distinguishing recurrent sarcoma from postsurgical scarring, according to a study published in the May issue of Radiology.

MRI performed after surgical resection of soft-tissue sarcoma is done to assess the surgical site for recurrent tumor. This must be differentiated from postoperative inflammation and fibrosis, which can be challenging, as many characteristics are similar.

Lead author Filippo Del Grande, MD, MBA, MHEM, of the Johns Hopkins University Hospital in Baltimore, and colleagues investigated the added value of functional MR sequences—dynamic contrast-enhanced MRI and diffusion-weighted imaging with apparent diffusion coefficient (ADC) mapping—for the detection of recurrent sarcoma after surgical resection.

The study group included 37 patients referred for postoperative surveillance after resection of soft-tissue sarcoma. Imaging included conventional and functional sequences, and recurrences were confirmed with biopsy or resection. Two readers independently recorded the signal and morphologic characteristics with conventional sequences, the presence or absence of arterial enhancement at dynamic contrast-enhanced MRI and ADCs of the surgical bed. The accuracy of conventional MRI in detecting recurrence was compared with that of the addition of functional sequences.

The study’s results revealed six histologically proven recurrences in the 37 patients. The sensitivity and specificity of MRI in the detection of recurrence were 100 percent and 52 percent, respectively, with conventional sequences. The sensitivity and specificity were 100 percent and 97 percent with the addition of dynamic contrast-enhanced MRI, and 60 percent and 97 percent with the addition of diffusion-weighted imaging and ADC mapping.

The average ADC of recurrence, 1.08 mm², was significantly different from those of postoperative scarring at 0.9 mm² and those of hematomas at 2.34 mm². The addition of a dynamic contrast-enhanced MR sequence reduced the false-positive rate from 48 percent to 3.2 percent.

“Although recurrent sarcoma can be detected with high sensitivity by using a conventional MR imaging protocol, the addition of functional MR sequences for postsurgical surveillance may decrease the false-positive detection rate,” wrote the authors. “Because postsurgical surveillance for sarcomas routinely includes a contrast-enhanced MR examination, a protocol that includes dynamic contrast-enhanced MR imaging requires no additional contrast material administration.”