Standard nuclear scintigraphy of parathyroid cancer produces enough false positives for patients with multigland disease to lead researchers to recommend rapid intraoperative parathyroid hormone assay along with preoperative technetium-99m sestamibi imaging to assure that all lesions have been removed.
Tc-99m sestamibi planar and SPECT are the imaging modalities of choice for surgery planning for primary hyperparathyroidism. About 15% of cases involve multigland disease, with the rest involving single-gland disease.
While imaging is not required before traditional open surgery to remove parathyroid tumors, surgeons have come to rely on nuclear scintigraphy to identify the location of parathyroid adenomas as they have adopted minimally invasive excision, according to Dr. William G. Spies, a professor of radiology at Northwestern University.
A report published last year by K. J. Nichols, Ph.D., and colleagues in the nuclear medicine and molecular imaging department at North Shore-Long Island Jewish Health System in Manhasset, NY, indicated the presence of single- or multigland disease has a big impact on the ability of sestamibi imaging to detect ectopic lesions (Radiology 2008;248[1]:221-232). The sensitivity of technique dropped from 90% for single-gland disease to 66% for multiglandular disease, Nichols said.
At the 2009 RSNA meeting, Nichols presented extensive results about how various factors can affect the procedure’s sensitivity. The single-center retrospective analysis of 662 patients was 92% sensitive to the presence of parathyroid lesions, but that performance declined from the influence of several factors.
Cases involving normal calcium levels were only 67% sensitive, compared with 86% sensitivity for cases of elevated calcium, Nichols reported. The presence of adenoma contributed to scans that were 95% sensitive compared with 76% sensitivity for the presence of nonadenomas, he said.
Sensitivity decreased progressively with decreasing lesion weight. For the quartile accounting for the heaviest lesions (mean weight of 2520 mg), imaging was 92% sensitive to identifying the lesion. For the quartile accounting for the lightest lesions (mean weight of 100 mg), sensitivity dropped to 68%.
Sensitivity also decreased progressively with an increasing number of lesions, Nichols said. Imaging sensitivity was 96% for patients harboring a single lesion, but it dropped to 46% for patients who had four lesions, he said.
