Abstract
1471
Objectives To revisit the clinical value of dual time point (DTP) FDG PET/CT imaging in patients referred for assessment of clinically concerning pulmonary nodules.
Methods This is a retrospective study of 69 patients referred for evaluation by 18-FDG PET/CT of a clinically concerning pulmonary nodule, between July 2012 and September 2015 at a military medical center. PET/CT was acquired at 1 and 2 hrs (early and delayed scan) after 18F-FDG injection. The maximum standardized uptake value (SUVmax) was calculated of each nodule that had focally greater than lung background uptake. Any solid, semi-solid or ground-glass nodule was accepted. A positive for malignancy result was defined as greater than 10% increase between the early and delayed scan. A negative result was defined as less than a 10% increased uptake, stability, or decreased uptake between the early and delayed scans. The “gold standard” for comparison was either a biopsy result, or a greater than one year follow-up chest CT or PET/CT. Only cases with a “gold standard” for comparison were accepted. Simple sensitivity and specificity were calculated.
Results The number of true positive cases was 26, of false negative cases 6, of false positive cases 12, and of true negative cases 25. These translate into a sensitivity of detecting cancer in a malignant nodule of 78.8% and specificity to exclude cancer in a non-malignant nodule of 67.6%. If excluding nodules less than 10 mm or ground-glass nodules, the sensitivity increases to 89.7%. In comparison to initial only or single time point (STP) imaging with positivity for malignancy defined as SUVmax at 2.5 or greater, the sensitivity is not significantly changed at 78.1%, rising to slightly less than with DTP when excluding nodules less than 10 mm or ground-glass nodule to 85.7%. Specificity is also not significantly different for STP imaging only, calculated at 66.7%.
Conclusions Dual-time-point 18F-FDG PET-CT imaging is of questionable greater usefulness than single-time point imaging for differentiating malignant from benign pulmonary nodules, showing a slight benefit in only sensitivity if excluding small or ground-glass nodules.