Padmini Gopalan MBBS, Presenter: Nothing to Disclose

Eleanor Lorenz MBChB, Abstract Co-Author: Nothing to Disclose

To analyse the relative accuracy of qualitative and quantitative PET data in differentiating benign from malignant adrenal masses. To assess if routine use of quantitative maximal SUV or SUR data is necessary. To evaluate whether combined CT densitometry data and quantitative SUV PET maximise the specificity.

Retrospective analysis of 38 patients with adrenal masses referred for PET CT. The study group included both known primary extra adrenal malignancy and suspicious primary adrenal lesions. A cohort of 34/38 patients had both qualitative and quantitative analysis. Validation for the detected adrenal lesion was by histology, follow up CT and MR scans. Reference standards used: SUV adrenal to liver ratio: > 2 is considered malignant, 1.5-2 is equivocal and less than 1.5 is benign. SUV max more than 2.68 is highly suspicious for malignancy. CT attenuation value cut off for benign adrenal lesions is < 10HU.

16/38(42%) were biopsy proven malignant lesions. The sensitivities for quantitative SUV versus visual analysis were 86% and 87% ; Specificities were 78% and 83%. Positive predictive values were 81and 82% ; negative predictive values were 88% and 88% respectively for quantitative and qualitative analysis. Haemorrhage can cause high SUV values resulting in false positive result. Incorporating CT densitometry and SUV max value seems to improve the specificity.

Qualitative and quantitative analysis showed reasonably comparable results and were deemed complementary. Prospective SUV measurements may or may not sway towards quantitative analysis.

The common conundrum is to differentiate benign adrenal adenomas from metastatic disease. Debate prevails whether quantitative or qualitative PET CT analysis is superior in characterising adrenal masses. Mester et al study favoured quantitative SUV PET data with a specificity of 92%. Boland et al study concluded routine quantitative analysis is not necessary as SUV test specificity to detect malignancy was 78%.

Gopalan, P, Lorenz, E, Qualitative versus Quantitative PET CT Characterisation of Adrenal Masses.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14008454.html