Role of PET and PET/CT in Anticancer Drug Therapy Response Evaluation

Anti-cancer drug development is a major area of research. New imaging techniques provide a novel method for anti-cancer drug development and monitoring response to therapy by targeting functional metabolic activity at cellular level. The current assessment of the response to therapy in solid tumors based on measurement of the changes in tumor size have many limitations. Positron emission tomography (PET) has been used to measure changes in drug induced metabolism, cellular proliferation and tissue perfusion. Also, changes induced by immuno-modulating drugs such as apoptosis, telomere activity, growth factor levels and many more can be studied using specific radiolabelled PET tracers. Initially PET was used alone without any computed tomography (CT) or magnetic resonance imaging (MRI) hybridization. Since there are few limitations associated with PET alone, a novel combined PET/CT system has recently been built that improves the ability to correctly localize and interpret radiotracer uptake. Hybrid PET/CT scanners provide both the anatomical and functional aspects of the tissue. PET and PET/CT have been found to be very useful in various cancers. In the present study we have investigated role of PET/CT as a predictor of early response to chemotherapy in locally advanced breast cancer patients, lymphoma, pediatric cancer, lung cancer, etc. We have performed more than 14000 PET/CT at our institute. We have found that fluorine-18 fluoro-deoxy-glucose (18F-FDG) PET/CT plays important role in early assessment of treatment response in various cancer patients. A positive PET/CT scans after the completion of therapy is a strong predictor of residual disease, whereas, a negative study is associated with complete remission in these patients.