18F-Sodium Fluoride Positron Emission Tomography (Naf-18-pet/ct) Radiomic Signatures to Evaluate Responses to Alpha-Particle Radium-223 Dichloride Therapy in Osteosarcoma Metastases.

Patients with osteoblastic metastases from high risk osteosarcoma continue to have a poor prognosis after progression from standard-of-care multi-agent chemotherapy. In a first-in-human dose escalation trial of bone targeted Radium 223 dichloride alpha-particle therapy in 18 patients with advanced osteosarcoma only 1 patient responded based on conventional Response Evaluation Criteria in Solid Tumors (RECIST). (NaF)-F-18 PET response Criteria in Solid Tumors(NAFCIST), based on Sodium fluoride-18 ((NaF)-F-18) positron emission tomography (PET)-CT was developed to better evaluate bone specific response. To further appreciate the spatial and temporal heterogeneity of the partial or mixed responses, a radiomics method was developed. Analyses were performed with F-18-sodium fluoride positron emission tomography imaging studies before and after alpha-particle therapy. Radioactive F-18(-) -atom concentrations were measured in softtissues, in approximately 1000 concentration data points for F-18(-) per 1 cm(3) metastatic tumor. Data was analyzed from the SUV intensity values, the histogram of intensities and entropy values. Radiomics may inform intra-tumoral and inter-tumoral heterogeneity in response of bone forming osteosarcoma to alpha particle therapy. Each patient (and each tumor) represents an "N of 1" case and warrants in depth analysis individually. (C) 2021 Elsevier Inc. All rights reserved.