Sestamibi SPECT Intensity Scoring System in Sporadic Primary Hyperparathyroidism

Most cases of sporadic primary hyperparathyroidism (PHP) are due to a single parathyroid adenoma and can be treated with minimally invasive parathyroid exploration guided by sestamibi SPECT imaging and intraoperative parathyroid hormone monitoring. Successful surgery depends on identification of the 10–15% of patients with multiglandular disease. Failed initial parathyroid exploration is both costly and morbid. We examined whether a sestamibi SPECT scoring system could predict anatomic findings in patients with PHP.

Prospective data from 1,061 consecutive patients undergoing initial parathyroid exploration for PHP from March 6, 2000 to September 28, 2007 were reviewed. One nuclear medicine physician performed independent blinded review of 577 available dual time-point sestamibi SPECT scans, and scored the results into 1 of 5 categories: 0—negative, 1—possible, 2—probable, 3—definite adenoma, or 4—multiglandular disease. Intraoperative findings and outcomes at >5 months follow-up were examined. Chi-square and nonparametric analyses were used to evaluate variables for correlation.

Among patients with sestamibi SPECT scan results classified as either 0—negative or 1—possible adenoma, only 211/262 (81%) had a single adenoma, compared to 263/288 (91%) patients with scan results classified as 2—probable or 3—definite adenoma (p < 0.001). Positive predictive values increased in stepwise correlation with sestamibi SPECT image intensity: 1—possible 78.5%, 2—probable 94.3%, and 3—definite adenoma 98.8%. Multiglandular disease was present in 31/144 (22%) patients with a 0—negative scan versus 13/166 (8%) patients with a 3—definite adenoma scan (p = 0.0005). Only 7/27 (26%) patients with scans classified as 4—multiglandular had actual multiglandular disease. Negative scan results were associated with a greater risk of operative failure (p < 0.001).

A simple scoring system based on sestamibi SPECT intensity can predict the likelihood of single adenoma in PHP. Even the best localizing study cannot exclude multiglandular disease preoperatively. Negative sestamibi SPECT scans are associated with a higher rate of operative failure. Because sestamibi SPECT scans of any category do not reliably identify multiglandular disease, expert surgeons must use validated adjuncts to avoid operative failure.