Molecular imaging of metastatic atrial angiosarcoma with positron emission tomography (PET) tracer 3'-deoxy-3'[(18)F]-fluorothymidine, [(18)F]-FLT imaging and early response evaluation

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). Na¹⁸F PET response Criteria in Solid Tumors(NAFCIST), based on Sodium fluoride-18 (Na¹⁸F) 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 ¹⁸F-sodium fluoride positron emission tomography imaging studies before and after alpha-particle therapy. Radioactive ¹⁸F^- -atom concentrations were measured in soft-tissues, in approximately 1000 concentration data points for ¹⁸F^- per 1 cm³ 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.

Molecular Imaging with 3'-deoxy-3'[(18)F]-Fluorothymidine (18F-FLT) PET/CT for Early Response to Targeted Therapies in Sarcomas: A Pilot Study

Although 3′-deoxy-3′[(18)F]-fluorothymidine (FLT)-positron emission tomography (PET) has been utilized for tumor response assessment to neoadjuvant chemotherapy in soft tissue sarcomas, it has not been exploited for the assessment of early response to systematically targeted therapies. Herein, we investigated the ¹⁸F-FLT PET/CT kinetics in patients with sarcoma who received targeted therapies. Among 15 patients with sarcoma who underwent ¹⁸F-FLT PET/CT, 5 patients (33%) patients were imaged at three time points: At baseline and at 1–15 weeks (MDM2-inhibitor treatment), and 10 patients (67%) were imaged twice: At baseline and at 1–4 weeks (MDM2 inhibitor, n = 5; c-met inhibitor n = 5). The patients with sarcoma had a total of 18 identifiable tumors. Twelve of 15 patients (80%) demonstrated ¹⁸F-FLT concentrations changes early, i.e., at 1–4 weeks. Eight patients responded (53.3%), four patients progressed (26.7%) based on FLT change of more than 10% increase, and three patients (20%) demonstrated no change. ¹⁸F-FLT PET/CT may be used for early response imaging to molecularly targeted therapies in patients with sarcoma. Further larger studies in specific sarcoma sub-types are warranted.