Does magnetic resonance imaging accurately predict residual disease after unplanned excision of soft-tissue sarcomas?

Often, it is difficult to assess the presence of residual disease after an unplanned excision in soft-tissue sarcomas. Inadequate excision leads to disease recurrence and inferior oncological outcomes while unnecessary excision may lead to additional surgical procedures with inherent morbidity and increased cost of treatment. There is a paucity of literature comparing the preoperative imaging findings with the final histopathology report to accurately assess the presence of residual disease.

The clinical details of 55 patients who had oncological scar excision after unplanned prior excision were retrieved. Histopathological evaluation of scar was compared with presurgery magnetic resonance imaging (MRI) for the presence of residual disease. Sensitivity, specificity, and positive and negative predictive value (NPV) of MRI for detection of residual disease were calculated.

On MRI, residual disease was seen in 28 cases, no disease in 24 cases whereas findings of three patients were indeterminate. On final histopathology, residual disease was present in 30 (55%) patients whereas no residual tumor was seen in 25 (45%) patients. Two patients in whom MRI suggested the presence of residual disease had no tumor on final histopathology. No evidence of residual disease was reported in MRI of 24 patients. Of these, twenty patients were confirmed to have no tumor on final histopathology, whereas four patients had a residual tumor. Sensitivity: 86.66%, specificity: 90.90%, positive predictive value (PPV): 92.85%, NPV: 83.33%.

MRI can aid in preoperative planning by identifying the site and extent of the previous surgery. It has a high PPV (92%) for detection of residual disease. However, a negative scan (NPV 83%) does not reliably exclude the presence of residual disease.