Imaging biomarkers in the era of targeted therapies

A variety of imaging techniques and technologies are helping clinicians to evaluate treatment success as well as to determine the stage and spread of disease in patients.

Yesterday, ESMO joined forces with the European Association of Nuclear Medicine (EANM) and the European Society of Radiology (ESR) for a joint symposium entitled ‘Imaging biomarkers in the era of targeted therapies’.

Professor Elisabeth de Vries from the University Medical Centre Groningen, Groningen, the Netherlands, opened the session with an overview of imaging approaches in cancer, where she outlined the important role of imaging in oncology and emphasized the need for oncologists and radiologists to work together in order to maximize the potential of imaging biomarkers in oncology, particularly in the current era of targeted therapy.

Dr Jan Bogaerts from the EORTC, Brussels, Belgium, discussed the basis of Response Evaluation Criteria in Solid Tumours (RECIST), a widely applied method to assess solid tumour response and progression. He outlined the technique’s strengths, weaknesses and ongoing efforts to improve this methodology. For example, in 2009 RECIST v1.1 was published, which included a host of modifications and additional specifications and clarifications, including a restriction in the number of target lesions to a maximum of five and special considerations for lymph nodes.

However, work on the existing EORTC RECIST database is ongoing, which includes efforts to collect FDG-PET data for evaluation and potential inclusion into the methodology.

Dr Yves Menu from Saint Antoine Hospital, Paris, France, continued the discussion on RECIST, as he described the advantages of standardizing assessment processes and the technical requirements that practitioners need to consider when using RECIST. Dr Menu argued that standardization also has limitations since certain tumours, such as GIST and HCC, may also need adapted criteria. “Morphology does not summarize tumour biology,” he remarked, “so adding structural, metabolic and/or functional information is desirable.”

New developments in oncologic imaging, including how functional imaging influences treatment decisions in patients with malignancy, were discussed by Dr Anno Graser from the University of Munich in Germany. In his talk, he presented results of studies using functional CT and MRI in humans and animals treated with antiangiogenic drugs. Based on his findings, he concluded that advanced imaging, including functional imaging tests, can detect early response to treatment and can be used to aid treatment decisions.

Professor Stefano Fanti from the University of Bologna, Italy, talked about the molecular imaging techniques, particularly Positron Emission Tomography (PET), that are complementary to conventional imaging methods. Hybrid PET-CT scanners combine functional data with anatomic details to increase diagnostic accuracy. Professor Fanti also introduced a wide range of alternative tracers to FDG for PET scans. “Some malignancies do not show an increase in glucose consumption and are almost invisible with FDG,” he said, “therefore other tracers have been developed to study alternative metabolic pathways.” Indeed, tracers already in clinical use include choline (labeled with 11C or 18F), a marker of cell membrane metabolism particularly useful for prostate cancer detection; 18F-tyrosine and 11C-methionine, markers of protein metabolism that are successfully employed for CNS neoplastic diseases; and 18F-DOPA and 68Ga-DOTA-NOC, which are both useful in neuroendocrine tumours.

Finally, Professor Wim Oyen from the Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands, ended the symposium with his perspective on how clinicians are using advanced imaging techniques to address a variety of challenges. He highlighted how molecular imaging with radiopharmaceuticals is aiding patient evaluation before targeted therapy is initiated. “The ability of FDG-PET to predict response of metastatic GIST to imatinib became the role model for the potential of molecular imaging to provide clinically relevant answers within days after the start of treatment,” he said.

In his talk, Professor Oyen also gave an overview of clinical studies that have incorporated the use radiolabelled therapeutics, for example to visualize monoclonal antibody drug targets. “The time has come to systematically position advanced imaging for treatment selection in clinical trials,” he concluded.