Quarter-Century PET/CT Transformation of Oncology: Lymphoma

The use of quantitative metrics, such as metabolic tumor volume (MTV), and total lesion glycolysis (TLG) in a research setting in several lymphoid and solid tumors has shown promise.52-54 MTV is the metabolically active volume of the lesion, based on a predetermined SUV threshold. The TLG is derived as a product of the MTV and the mean SUV of the lesion. The MTV of lesions throughout the body can be summed to give a total body MTV (TMTV), which is representative of the global metabolically active disease burden. A retrospective study of 185 patients with follicular lymphoma who were receiving combination immunechemotherapy showed that TMTV calculated on baseline PET was highly prognostic for both progression -free survival (PFS) and overall survival (OS).55 However, there are challenges with these measurements, including lack of standardization (SUV threshold to be used for segmenting), suboptimal reproducibility of cutoff values and time required to perform these measurements in a clinical setting.56 Although artificial intelligence -based tools are attempting to solve several of these limitations. The development and validation of artificial intelligence and radiomics-based tools has shown promise in disease prognostication.57 It is anticipated that the use of quantitative metrics and radiomic analyses will grow significantly, especially with the advent of reliable automatic segmentation methods that can be deployed in busy clinical practices.58 The development of new radiopharmaceuticals such as those targeting specific cellular/ subcellular structures in the tumor microenvironment that can aid in both diagnosis and therapy is an area of active research.59,60 We have come a long way in the integration of PET/CT in management of lymphomas, and with the new developments in radiopharmacy and physics, there will be additional avenues for imaging to aid in the management of these patients.