PURPOSE: Bone and soft tissue tumors are rare. There is a variety of types and each one has its own particular behavior, treatment and patient outcome. The assessment of treatment response following the 3rd cycle of chemotherapy is one of the most important aspects of patient care, as therapeutic options and the timing of surgery may vary depending on the achievement of response. Hence, we focused on the advanced imaging technique, proton magnetic resonance spectroscopy (1H MRS), aiming at improving the diagnostic accuracy and the tumor response to therapy, based on the absolute concentration of choline (Cho) as biomarker of malignancy. METHODS: Twenty patients were studied. All of them had a pathological diagnosis after biopsy. MRI examinations were performed using a 1.5 T MR scanner (Avanto; Siemens, Erlangen, Germany). Single-voxel 1H MR spectroscopy was performed by using a PRESS with TR/TE 1530/100 ms, before chemotherapy and after the 3rd cycle. 1H MRS was processed in LCmodel. RESULTS: Of 20 patients, 7 responded to neoadjuvant chemotherapy and 13 did not. In responders, the mean concentration of tCho before therapy was 4.7±2.5 mmol/kg, which showed statistically significant reduction after therapy. In non-responders, the mean tCho concentration before therapy was 2.9±0.9 mmol/kg which remained the same or increased after the 3rd cycle of neoadjuvant chemotherapy (2.7±2.5 mmol/kg; range from 2.05 to 5.79 with no statistical significance). Compared to reference healthy group, tCho concentrations were increased in all cases.