Metabolic monitoring of MRgFUS treatment in bone metastasis using 18F-FDG PET/CT: A case report

Objectives: Magnetic Resonance-guided Focused UltraSound (MRgFUS) is an innovative method for the bone metastasis treatment both for the pain palliation and for the cancer tissue ablation. Aim of this work was to evaluate the MRgFUS technique efficacy by 18F-FDG PET/CT quantitative studies in a clinical case in which the lesion was accessible to the US beam. Methods: A 62 years old man with a pelvic bone lesion from a kidney carcinoma primitive was studied by PET/CT before (I), at 90 (II) and at 180 (III) days after the MRgFUS treatment. The treatment outcome was assessed at I, II and III by: 1) a pain perception evaluation: the patient has been asked to evaluate his pain in a scale from 0 (no pain) to 10 (high pain), 2) an evaluation of metabolic changes within the lesion as effect of the tissue ablation: qualitative and quantitative assessment of the PET/CT images was performed. Mean SUV was calculated, with and without Partial Volume Correction (PVC) by a semi-automatic method [IEEE Trans Nucl Sci 2011, vol.58(3), pp.736-47]. Mean SUV variation (SUV) during follow-up was calculated and the metabolic tumor response (EORTC criteria) was derived. Results: Pain decreased from 9 (I) to 2 (in both II and III) as confirmed by the patient. A reduction of uptake within the treated lesion was qualitatively observed on the PET/CT images of the 3 studies. Quantitative results (see Table): SUV within the bone lesion showed a decrease of 35.1% (I vs II) and 38.3% (I vs III) without PVC, and a decrease of 26.6% (I vs II) and 31.4% (I vs III) with PVC, indicating a partial metabolic response. PVC reduced SUV but did not change the tumor response classification. Stable SUVs were observed in II and III (% difference <5% without PVC and <7% with PVC). Conclusions: This case report proves the MRgFUS validity for the bone metastasis symptomatic treatment. SUV changes during follow-up indicates that MRgFUS is able to enhance the inflammatory response by the cell-repair effects.