This study explores changes in metabolic tumor volume, metabolic tumor
diameter, and maximum standardized uptake value (SUVmax), for earlier
and more accurate identification of lymphomas’ response to treatment
using F-18-FDG PET/CT. Pre-and post-treatment PET/CT studies of 20
patients with Hodgkin disease (HL) and 7 patients with non-Hodgkin
lymphoma (NHL) were retrospectively selected for this study. The
diameter and volume of the metabolic tumor was determined by an in-house
developed adaptive local thresholding technique based on a 50%
threshold of the maximum pixel value within a region. Statistical
analysis aimed at exploring associations between metabolic size
measurements and SUVmax and the ability of the three biomarkers to
predict the patients’ response to treatment as defined by the four
classes in the European Organization for Research and Treatment of
Cancer (EORTC) guidelines. Results indicated moderate correlations
between % change in metabolic tumor volume and % change in metabolic
tumor maximum diameter (R=0.51) and between % change in maximum
diameter and % change in SUVmax (R=0.52). The correlation between %
change in tumor volume and % change in SUVmax was weak (R=0.24). The %
change in metabolic tumor size, either volume or diameter, was a “very
strong” predictor of response to treatment (R=0.89), stronger than
SUVmax (R=0.63). In conclusion, metabolic tumor volume could have
important prognostic value, possibly higher than maximum metabolic
diameter or SUVmax that are currently the standard of practice. Volume
measurements, however, should be based on robust and standardized
segmentation methodologies to avoid variability. In addition, SUV-peak
or lean body mass corrected SUV-peak may be a better PET biomarker than
SUVmax when SUV-volume combinations are considered