False-Positive Rate of Positron Emission Tomography/Computed Tomography for Presumed Solitary Metastatic Adrenal Disease in Patients with Known Malignancy

Abstract

Purpose

The aim of this study was to determine the diagnostic accuracy of positron emission tomography (PET) in cancer patients undergoing adrenalectomy for presumed metastatic disease, utilizing the gold standard of histopathology.

Methods

We retrospectively reviewed all adrenalectomies for metastatic disease performed at our institution over the last 12 years. Preoperative PET scans were compared with final pathology reports. Statistical analyses were performed with Fisher’s exact test for categorical variables and Student’s t test for continuous variables.

Results

Forty-nine adrenalectomies were performed for metastatic disease. Thirty had preoperative PET imaging and were included in this analysis. Mean age was 65.5 ± 13.6 years (29–91) and 54 % were male. Mean size was 3.8 cm (0.4–7.1). Primary tumor distribution was 61 % (n = 17) pulmonary; 11 % (n = 3) breast; 7 % (n = 2) gastric; 7 % (n = 2) renal; and 4 % (n = 1) each of brain, lymphoma, melanoma, and uterine. Mean standardized uptake value (SUV) was 11 ± 7.3 (3.2–30.0). Final pathology revealed that 80 % (25/30) were positive for metastatic disease and 20 % (5/30) were negative. The positive predictive value of PET in correctly identifying adrenal metastatic disease was 83 % (24 true-positive cases and 5 false-positive cases); there was one false-negative PET. False-positive PET results were not correlated with sex (p = 0.35), age (p = 0.24), or maximum SUV units (p = 0.26).

Conclusions

The 20 % false-positive rate for PET-positive adrenalectomies performed for metastatic disease should warrant its inclusion in preoperative counseling to the patient and interaction with the treating oncologist.