SNMMI 2016: FDG-PET Evaluates Immunotherapy for Non–Small Cell Lung Cancer
Researchers at the 2016 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) presented a means of evaluating an immunotherapy that fights off non–small cell lung cancer (NSCLC) by strengthening a patient’s own immune system (Scientific Paper 134). Due to NSCLC’s relative insensitivity to chemotherapy, researchers have been increasing the use of immunotherapies, including a class of monoclonal antibodies that serve as immune checkpoint blockade inhibitors.
In this study, researchers investigated the immunotherapeutic atezolizumab (Tecentriq), which inhibits activity between the programmed death 1 (PD-1) receptor expressed on certain immune cells and the programmed death ligand-1 (PD-L1), a transmembrane protein found on the surface of tumor cells.
FDG PET
Researchers tracked the ability of atezolizumab to bolster immunity against NSCLC with positron-emission tomography (PET), which provides a visualization of physiologic functions of the body with the aid of an injected imaging agent combining a tiny amount of radioactive material and a molecular compound called fluorine-18 fluorodeoxyglucose (F-18 FDG). This radiotracer mimics glucose as it is taken up as fuel by the body. FDG-PET allows clinicians to see areas of increased metabolic activity in cells, also known as hypermetabolism, a hallmark of malignant tissues, and change in metabolic activity following drug treatment.
This multicenter study included a total of 138 patients with NSCLC from 28 clinical institutions in five different countries. All subjects received 1,200 mg of atezolizumab administered intravenously in 3-week intervals. Researchers used quantitative PET that measured FDG retention as a sign of metabolic activity, both at baseline before study treatment, and again after 6 weeks of treatment with atezolizumab.
Study Findings
The study revealed that higher baseline tumor volumes of FDG were predictive of reduced patient survival, meaning that greater active tumor volume at the start of therapy was a sign of lower survival. In addition, a further increase in tumor volume at 6 weeks was a sign of decreased patient survival. Although atezolizumab and other immune checkpoint inhibitors work differently than conventional chemotherapy, FDG-PET may be used with either treatment to help doctors evaluate how NSCLC patients may respond to therapy.
“This study is the first to prospectively evaluate FDG-PET imaging in a phase II trial of lung cancer patients receiving the novel immune checkpoint inhibitor atezolizumab,” said Jill Fredrickson, PhD, a clinical imaging scientist in the Department of Early Clinical Development at Genentech. “These findings help define the potential role of FDG-PET as a prognostic and predictive biomarker in the treatment of lung cancer with such immunotherapeutics.”
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
