An integral part of the workup of indeterminate solitary pulmonary nodules is 18F-flurorodeoxyglucose positron-emission tomography (FDG PET/CT) [1]. The FDG avidity of a nodule can reduce the number of unnecessary invasive procedures for benign nodules and the associated risk to the patient [2-3]. Standardised uptake value (SUV) is a measure of the relative FDG uptake in a pulmonary nodule. A maximum SUV (SUVmax) of greater than or equal to 2.5 has been recommended as a cut-off to differentiate between benign and malignant nodules, where nodules...

Patient population: A single centered, retrospective audit was performed of 214 patients who underwent FDG PET/CT over a one year period between April 2017 and April 2018 for indeterminate solitary pulmonary nodule, suspected or proven primary lung malignancy. Lesions with a positive histology obtained from either a lung biopsy or surgical resection were included in the malignant group. The histological malignant subtype was recorded for subgroup analysis. Lesions that were stable for two years, resolved or reduced in size on CT or had a negative...

A total of 155 patients were included and 59 patients were excluded from the study. The average age was 68 years old (range 39 to 89 years). There were 44 patients (28%) in the benign group and 111 patients (72%) in the malignant group (Figure 1). The different subtypes of primary lung cancer are shown in Figure 2. [Fig 1] [Fig 2] The benign group had an SUVmax range of 0.51 to 13.50, mean 2.64 (95% CI 1.90 – 3.38) and standard deviation of 2.43....

Using an SUVmax cut-off of 2.5 is appropriate with high negative predictive value of 96% and sensitivity 97%. In our data, applying this SUVmax cut-off only missed three malignancies out of 111. However, of these false negatives, two were at the lower limits of size for spatial resolution for FDG PET (8mm) [5, 8], suggesting caution should be used when applying SUVmax in smaller nodules. Whilst specificity is increased by raising the SUVmax threshold this leads to an unacceptable increase in false negatives. Conversely, reducing...

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