Early Metabolic Response as a Predictor of Treatment Outcome in Patients With Metastatic Soft Tissue Sarcomas.

Twenty STS patients underwent FDG-PET scans at baseline, two- and eight-weeks following treatment with pazopanib. The FDG-PET scans were evaluated by quantitative PERCIST analysis and visually by an independent nuclear medicine physician and related to RECIST1.1 outcome at eight weeks.

In this heterogeneous STS patients' cohort, early FDG-PET/CT identified a substantial part of pazopanib non-responders.

After eight weeks of therapy, 14 out of 20 patients had discontinued pazopanib due to tumor progression identified radiologically ('non-responders' n=12) or toxicity (n=2). Quantitative FDG-PET scoring at two weeks, according to PERCIST guidelines, identified 25% (3 of 12) of the patients radiologically as non-responders versus 42% (5 of 12) identified by visual response analysis.

Pazopanib is approved for advanced soft tissue sarcoma (STS) patients. The aim of the study was to examine the usefulness of (¹⁸F)-Fluorodeoxyglucose-positron emission tomography/ computed tomography (FDG-PET/CT) imaging for early evaluation of the response of STS patients to pazopanib, as well as the association between pazopanib pharmacokinetics and early metabolic response.