Methods: This exploratory analysis evaluated the outcomes of PET/MRI in 21 patients with STS in different treatment settings: (a) neoadjuvant setting, (b) metabolic-driven local therapy in metastatic sarcoma, and (c) palliative treatment. For examination we used an Ingenuity PET/MR system (Philips Healthcare). It combines a 3-Tesla MRI and a PET scanner with time-of-flight technology.
Results: PET/MR shows a high contrast imaging without significant artifacts or distortions. (a) Four patients with high-risk sarcoma (3 rhabdo, 1 pleomorphic) completed the planned neoadjuvant therapy. Change in tumor size did not correlat with pathologic response, whereas surgical outcome was well predicted by metabolic changes. Due to this finding the preplanned course of chemotherapy for one patient was changed. (b) To prolong disease stabilization of 3 patients with a remnant metabolic activity in a single spot they underwent a surgical resection of a single metastatic lesion or had a local radiotherapeutic approach. (c) In 3 patients with stable disease after first-line treatment with combination of anthracyline and ifosfamide persisting metabolic activity indicated a switch to another alternative 2nd line regime. Trabectedin as 2nd line therapy decreased metabolic activity that finally resulted in a tumor regression. Conclusions: To our knowledge this is the first report on patients with STS examined with whole-body-PET/MR. PET/MR is feasible in STS and may provide valuable information in treatment, monitoring and prognosis of patients with STS. This technique may help to choose accurate and on-time treatment option without unnecessary time delay. Further prospective studies to evaluate PET/MR in STS are warranted
