Diagnostic Value of MRI for Detecting Recurrent Soft-Tissue Sarcoma in a Long-Term Analysis at a Multidisciplinary Sarcoma Center

Background: To assess the long-term diagnostic accuracy of MRI for detecting recurrent soft-tissue sarcoma at a multidisciplinary sarcoma center.Methods: In all, 1055 postoperative follow-up MRIs of 204 patients were included in the study. MRI follow-up scans were systematically reviewed for true-positive/-negative and false-positive/-negative results in detecting recurrent tumor. Available pathological reports and follow-up MRIs were set as reference. Results: The median age of the patients was 55.3±18.2 years. Of the patients, 34.8% presented with recurrences. Here, 65 follow-up scans were true positive, 23 false positive, 6 false negative, and 961 true negative. The overall sensitivity and specificity of MRI for detecting recurrences were 92% and 98%, respectively, with an accuracy of 97%. For intramuscular lesions and after surgery alone the sensitivity was higher (95% and 97%) than for subcutaneous lesions and surgery with additional radiation therapy (83% and 86%, respectively), at similarly high specificities (96-98%). The 6 false-negative results were found in streaky (n=2) and small ovoid/nodular (n=4) recurring lesions. The false-positive lesions imitated streaky (n=14), ovoid/nodular (n=8), and polycyclic/multilobulated recurring tumors (n=1). All false-positive results were found in patients in whom the primary tumors were polycyclic/multilobulated in appearance.Conclusion: MRI shows a high diagnostic accuracy for detecting recurrent STS, with a high sensitivity and specificity. The diagnostic accuracy decreases in subcutaneous lesions and after surgery with radiation therapy, compared to intramuscular lesions and surgery alone. Radiologists should pay particular attention to streaky and small ovoid/nodular recurring lesions and patients with polycyclic/multilobulated primary tumors.