Strategies of assessing and quantifying radiation treatment metabolic tumor response using F18 FDG Positron Emission Tomography (PET).

The use of positron emission tomography (PET) using F18 labeled fluorodeoxyglucose (FDG) for both oncology disease staging and radiation therapy target volume delineation has steadily increased over the last decade, and FDG-PET is today readily available in all major medical centers. The goal of anti tumor treatment, including chemotherapy and/or radiation therapy is to diminish a tumor cell population, ideally to the state of total eradication. Reducing the number of viable tumor cells can lead to a reduction in anatomical tumor size, and may also be correlated with decreased FDG uptake. Efforts to assess tumor response to therapy have attempted to describe and quantify changes in glucose utilization, also referred to as metabolic tumor response. In this review, an attempt is made to present and discuss methodologies to assess and quantify tumor metabolic response to radiation therapy or chemoradiation treatment courses.