Background – 99mTc-sestamibi parathyroid scans with SPECT reconstruction are used to localise parathyroid adenomas pre-operatively in primary hyperparathyroidism to facilitate minimally invasive surgery. In clinical practice we noticed that a significant number of 99mTc-sestamibi parathyroid scans were negative. The aim of this study was to determine the rates of positive 99mTc-sestamibi parathyroid scans and the outcomes of patients with both negative and positive scans.
Methods – We performed a retrospective analysis of all patients who underwent a 99mTc-sestamibi parathyroid scan with SPECT reconstruction between August 2011 and July 2012 at Maroondah Hospital. Files were reviewed and all patients with primary hyperparathyroidism were included. Investigations including biochemistry, imaging, histology and type of surgery were analysed.
Results – Of the 61 patients who underwent 99mTc-sestamibi parathyroid scans, 17 did not meet criteria for primary hyperparathyroidism. Of the 44 patients with primary hyperparathyroidism, 24 (54%) scans localised an adenoma. Of these, 17 (70%) proceeded to surgery and in 13 (76%) the scan was concordant with surgical findings. 10 (59%) underwent minimally invasive surgery, 2 (12%) underwent 4 gland exploration, 3 (17%) underwent unilateral exploration and 2 (12%)had total thyroidectomies with parathyroidectomy.
Of the patients with a negative scan, 17 (80%) had a thyroid US and 1(5%) localised a parathyroid adenoma. Only 9 (43%) of the patients with negative scans underwent surgery, 3 (33%) underwent minimally invasive surgery, 4 (44%) had 4 gland exploration, 1(11%) had a total thyroidectomy and the last patient did not have surgical records available.
Conclusion - Almost half of all 99mTc-sestamibi parathyroid scans did not identify an adenoma. This study suggests that patients with a negative 99mTc-sestamibi parathyroid scan were less likely to proceed to surgery despite similar age and disease severity. This raises concern that patients with negative imaging may miss out on surgery that is otherwise indicated.