More than 85% of patients with primary hyperparathyroidism have a single parathyroid adenoma. However rates of multiglandular involvement reported in worldwide literature vary between 4 - 30%. Parathyroidectomy of all diseased glands is the only chance of cure.
Bilateral neck exploration has been the standard procedure with a cure rate of 95 - 99%. Since the emergence of better localizing image studies, namely ultrasonography (US), technetium-99 m sestamibi with single photon computed tomography (SPECT) and four-dimensional computed tomography, along with rapid intraoperative parathyroid hormone (IOPTH) monitoring, focused parathyroidectomy has become a valid alternative. Single parathyroid adenoma is localized in 70% of cases only with sestamibi, but its accuracy increases to 95 - 98% when in combination with ultrasonography. Although IOPTH mesure has advantages in confirming the cure, two disadvantages are clear. First a minimum of 20min is added to operative time, secondly the possibility of a false negative test which leads to an additional unnecessary neck exploration.
The question is: when there is preoperative concordance between US and sestamibi in adenoma localization, is intraoperative parathyroid hormone mesure necessary?
To answer this question, Bobanga and McHenry from Cleveland, published in "The American Journal of Surgery" a retrospective analysis of 127 patients submitted to focused parathyroidectomy between May 1994 and February 2016. Inclusion criterium was preoperative diagnosis of primary hyperparathyroidism due to a single gland adenoma, with concordance between US and sestamibi imaging with SPECT in identifying the lesion. Parathyroid hormone was mesure prior to surgery, five and ten minutes after excision. A decline above 50% and into the normal range 10 min following adenoma excision was used as a predictor of cure. Comparison was made between preoperative image and intraoperative findings.
Results are clear! Although all patients had their primary hyperparathyroidism cured, focused parathyroidectomy was successful in 94% of cases. Two patients had a single adenoma at a different gland, two patients had two adenomas, three patients had asymmetric parathyroid hyperplasia, meaning that in 7 patients (6%) an additional neck exploration was required to achieve the cut-off value in IOPTH decline.
The authors found that concordance in preoperative image exams (US and sestamibi with SPECT) has a positive predictive value of 94% in detecting a single adenoma. Additionally in 6% of patients intraoperative findings are different comparing to preoperative image, in whom IOPTH levels fail to fall more than 50%, and further neck exploration is necessary to excise the diseased gland(s). According to Bobanga and McHenry "the additional use of IOPTH in patients with two concordant preoperative studies lead to 100% cure of primary hyperparathyroidism".
Even though controversy remains whether IOPTH is necessary. Some institutions report a positive predictive value of 95-100% with combination of US and sestamibi, omitting IOPTH monitoring in those patients. However it seems clear that 7 patients (6%) in the series presented by Bobanga and McHenry would not have been cured if IOPTH mesure had been omitted. Interestingly the authors make reference to a scoring model proposed by Kebebew et al. to distinguish single gland disease from multi gland disease. Using this score there is a 100% positive predictive value of having a single gland disease if patients have concordant image studies, preoperative calcium >12mg/dL and preoperative PTH > twice the upper limit. Since the same values were found by Bobanga and McHenry, they conclude that probably in that very selected population focused parathyroidectomy could be performed without parathyroid hormone mesure. However more studies are needed to validate the Kebebew model.
Lastly I personally agree with the final idea presented by the authors. Although a positive predictive value >94% can be acceptable in some centers, doctors and patients must be aware that 6% of patients will not be cured and need further operation. That is why Bobanga and McHenry "advocate continued use of IOPTH even in patients with concordant preoperative studies", offering limited exploration and avoiding future reoperation.
Link to PubMed:
Dr. Carlos Eduardo Costa Almeida
General Surgeon