For stage I lung tumors, there is a significant relationship between growth rates, as measured by serial CT examinations, and the initial pre-treatment metabolic activities, as measured by FDG uptake, so FDG-PET may be used as additional prognostic tool for determining management, according to a study in the August issue of Clinical Radiology.

M. Tann, MD, from the department of radiology at the Indiana University School of Medicine in Indianapolis, and colleagues set out to determine the relationship between the metabolic activity measured by F18 FDG-PET and CT-derived tumor growth rates for stage 1 lung cancer.

The investigators retrospectively identified stage I lung cancer patients, who underwent FDG-PET, and who had at least two pre-treatment chest CT exams (51 patients). They defined metabolic activity by maximum lesion standardized uptake value (SUV) and maximum lesion-to-mean background activity (LBR).

Tann and colleagues determined the growth rates from serial CT volume measurements and the doubling time (DT) was calculated. They divided tumor growth rates into rapid (DT < 180 days), intermediate (DT = 180–270 days) and slow (DT > 270 days) groups.

The investigators found that rapid, moderate and slow DT in 22, 19, and 10 patients, respectively. The authors wrote that the means of SUV in the three groups (from rapid to slow growth rate) were 8.2 (4.8), 5.5 (4.5) and 2.2 (1.1), respectively and of LBR were 22.7 (10.1), 15.1 (12.6) and 6 (2.6), respectively.

They also found that there was a significant relationship between SUV and DT, as well as between LBR and DT.

The researchers said that their findings suggest that in patients in whom it is difficult to decide on the aggressiveness on treatment, F18 FDG-PET might be effective method.