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The Impact of Sestamibi Scanning on the Outcome of Parathyroid Surgery

Department of Surgery, College of Physicians and Surgeons of Columbia University, New York Presbyterian Hospital, New York, New York 10032

Address all correspondence and requests for reprints to: Paul LoGerfo, M.D., 161 Fort Washington Avenue, New York, New York 10032. E-mail: PL18{at}columbia.edu.

	Abstract

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Although sestamibi scanning has been shown to have greater sensitivity and specificity than other preoperative localization techniques for parathyroid adenoma, it is unclear whether preoperative scanning improves outcomes for parathyroid surgery. Data from 528 consecutive patients who underwent neck exploration for primary hyperparathyroidism by one surgeon were collected prospectively over a 5-yr period. Patients were classified by preoperative scanning status (no scan, positive scan, and negative scan), and outcomes were compared in terms of operative time, length of hospital stay, and cure rate. Patients who had undergone a previous parathyroid operation and patients who received alternate preoperative localization techniques (ultrasound, magnetic resonance imaging, and computed tomography) were excluded from the study. All scans were ordered by the referring physician—the surgeon made no recommendations for preoperative scanning. All groups were similar in terms of gender, age, anesthesia class, body habitus, and complication rate. There was no significant difference in cure rate between patients who had preoperative scanning (97.5%) vs. those who did not (99.3%); however, there was a significant difference in cure rate between the negative-scan group (92.7%) and the positive and no-scan groups (99.3%, P < 0.01). In patients without concomitant thyroid surgery, there was no significant difference in operative time between the no scan (42.4 ± 14.9 min) vs. the all-scan group (40.2 ± 15.2 min); however, there was a significant difference between the negative scan group (44.5 ± 21.9 min) and the positive scan group (38.5 ± 12.6 min, P < 0.01). There was no significant difference in length of hospital stay among the three groups. These results suggest that, although preoperative sestamibi scanning does not alter the outcome of parathyroid surgery, it does identify those patients who are less likely to be cured.

	Introduction

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PRIMARY HYPERPARATHYROIDISM affects 1 in 500 women and 1 in 2000 men annually (1). Since Felix Mandel performed the first successful pararthyroidectomy under local anesthesia in Vienna in 1925, bilateral neck exploration has been the standard surgical approach for patients with primary hyperparathyroidism (2). Several authors have demonstrated cure rates exceeding 95% with complication rates of 1–2% using this approach (3, 4, 5).

In 1991, the NIH consensus development conference panel evaluated ultrasonography, computed tomography, magnetic resonance imaging, and technetium thallium scans as possible noninvasive localizations tests of parathyroid adenomas. The panel determined that these imaging modalities were not indicated preoperatively in patients with primary hyperparathyroidism due to insufficient sensitivity and specificity. The panel also found that these preoperative studies did not reduce operative time, cost, or surgical failure (6). A second panel of experts recently convened to reevaluate the management of patients with asymptomatic hyperparathyroidsism. Despite improvements in technology over the last decade, including the introduction of technetium-99m sestamibi scanning, routine preoperative localization studies were again not recommended (7).

First used for myocardial perfusion studies, technetium-99m sestamibi scanning was soon applied to the localization of abnormally functioning parathyroid glands. A sensitivity and specificity as high as 91% and 99%, respectively, has been reported (8). Several authors have suggested that the use of preoperative sestamibi scanning in patients with primary hyperparathyroidism may reduce operative time, surgical failure rate, and complication rates (9, 10, 11, 12, 13, 14, 15). Other authors have suggested that sestamibi scanning can allow unilateral neck exploration (16). This paper examines the effects of preoperative sestamibi scanning on operative time, surgical cure rate, and length of stay.

	Materials and Methods

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Data from 594 consecutive patients who underwent bilateral neck exploration under local anesthesia by a single surgeon for primary hyperparathyroidism were collected prospectively over a 5-yr period from January 1996 to December 2001. Patients who were referred with a preoperative sestamibi scan were divided into negative (no abnormal gland visualized) and positive (one or more abnormal glands identified) groups. A positive scan was defined as a study that indicated a diseased parathyroid gland or glands regardless of whether the localization was correct. Patients who were referred without a scan underwent surgery without a preoperative localization study and were placed in the no scan group. All scans were ordered by the referring physician—the surgeon made no recommendations for preoperative scanning. Patients that had other preoperative localization studies were excluded. Patients with hyperplasia and reoperations were excluded. Patient characteristics evaluated included gender, age, anesthesia class, and body habitus. Outcomes measured included operative time, surgical cure rate, and length of stay. Surgical cure was defined a return of the serum calcium level to normal within 1 month postoperatively, and evidence of abnormal parathyroid tissue in the pathology specimen.

Surgical and anesthetic intervention

Patients are brought to the operative suite where intravenous access is established. The patients are lightly sedated with propafol before undergoing bilateral cervical block using a total of 60 cc of a 1:1 mixture of 0.5% lidocaine and 0.25% bupivicaine. Approximately 10 cc of local anesthetic is injected into the fat pad overlying the spinous processes of C3 and C4. Approximately 5 cc of anesthetic is injected on both sides of the trachea to block the upper poles, and the remaining volume is used to infiltrate the incision site. Conscious sedation is maintained throughout the case with iv midazolam and propafol. The patient is often awake enough to speak and follow commands.

A 4-cm transverse incision is made 1–2 cm below the cricoid cartilage. Skin flaps are developed and the strap muscles are separated in the midline. The middle thyroid vein is divided, and the thyroid is grasped with a clamp and rotated up and out of the wound, exposing the posterior thyroid and esophagus. All four parathyroid glands are identified, and the adenomatous glands are removed. The thymus is routinely explored transcervically if a lower pole gland cannot be found. The identified normal glands are biopsied only if an adenoma cannot be found.

After achieving hemostasis, the strap muscles are reapproximated in the midline, and the skin is closed with a subcuticular suture. The patient is monitored in the recovery room for 4 h and discharged home if there is no evidence of bleeding. The surgical and anesthetic approach were not altered by the presence, absence, or results of a preoperative localization study.

Statistical methods

Data were analyzed by t test for continuous variables and by chi-square test for discrete variables. Multiple linear regression was used to analyze continuous outcomes such as operative time. ANOVA techniques were used when comparing multiple groups. Length of stay was dichotomized to 0 d or greater than 0 d, requiring multiple logistic regression analysis.

	Results

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A total of 594 patients were evaluated in this study. Patients undergoing reoperation (n = 43), patients with hyperplasia (n = 16), and patients with a preoperative localization study other than a sestamibi scan (n = 7) were not considered in the analysis. Of the remaining 528 patients, 137 patients had no scan, 109 patients had a negative sestamibi scan, and 282 patients had a positive sestamibi scan.

Patient characteristics are summarized in Table 1. There were no differences in age, gender anesthesia class, or body habitus among groups. The percentage of patients with single and multiple adenomas was similar in all three groups. Carcinoma was a rare event. A similar percentage of patients had concomitant thyroid disease requiring thyroidectomy in each group. Four patients had mediastinal adenomas.

Outcome measures are summarized in Table 2. Patients that underwent preoperative scanning had a similar cure rate (97.5%) to patients that were not scanned (99.3%). Subgroup analysis demonstrated that patients with negative scans had a significantly lower cure rate (92.7%) than patients with either a positive scan (99.3%, P < 0.01) or no scan (99.3%, P < 0.01). Scanned patients had a similar mean operative time (40.2 ± 15.2 min) to patients that were not scanned (42.4 ± 14.9 min). Subgroup analysis revealed that patients with negative scans had a mean operative time that was 6 min longer than patients that had a positive preoperative scan (44.5 ± 21.9 vs. 38.5 ± 12.6 min, P < 0.01). There were no differences in the number of patients that were successfully treated as outpatients.

	Discussion

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Preoperative localization studies in patients with primary hyperparathyroidism theoretically hold the promise of improving surgical outcomes. The ability to localize a parathyroid adenoma could potentially increase the surgical cure rate, decrease operative time, avoid neck exploration in patients with mediastinal disease, and enable the surgeon to perform unilateral explorations extending the benefits of exploration under local anesthesia to more patients. Multiple modalities for localizing abnormal parathyroid glands have been used, with sestamibi scanning emerging as the technology with the highest sensitivity and specificity.

The sensitivity of sestamibi scans has been reported to range from 72–100% (17, 18). A recent metaanalysis involving 784 patients from 24 individual studies reported an overall sensitivity and specificity of 91% and 99%, respectively, for sestamibi localization of parathyroid adenomas in patients with primary hyperparathyroidism (8). The overall sensitivity (73%) and specificity (80%) in this series is lower than expected. This finding is likely multifactorial. Forty percent of the positive scans were performed at our institution, whereas only 32% of the negative scans were performed and read by our radiologists. Also, because we represent a major referral center, it may be that patients with negative scans were sent to us from the community more frequently than patients with positive scans.

Despite the high sensitivity and specificity reported in the literature, no author has demonstrated an improved cure rate using sestamibi scanning as an adjunct, which was substantiated by our study. In this series of 528 patients, the surgical cure rate was the same in patients that were scanned (97.5%) as those that were not scanned (99.3%). Patients with a negative preoperative scan had a significantly lower cure rate (92.7%) compared with patients with a positive scan (99.3%, P < 0.01). Although this information might be helpful for preoperative patient counseling, it would not change the operative approach for the patient.

Several other authors have found no benefit to preoperative sestamibi scanning. In a study of 66 patients, Lowney (19) found that preoperative sestamibi scanning had no impact on cure or treatment costs. Similarly, McHenry et al. (18) found that the lack of sensitivity of sestamibi scanning precluded its use in lieu of routine bilateral neck exploration in a study involving 124 patients. In an evaluation of 40 patients with primary hyperparathyroidism, Shen found that based on sestamibi scan results, their group would have had a 10% surgical failure rate had they not performed routine bilateral neck exploration. Shen et al. (17) predicts that the strategy of unilateral neck exploration based on preoperative scan results will reduce the surgical cure rate and increase cost. This contrasts with the experience of Udelsman who uses positive sestamibi scans imaged with single photon emission computed tomography as an entry criteria for his minimally invasive protocol. In a series of 100 patients, preoperative scanning combined with the intraoperative PTH assay, has enabled Udelsman to achieve a 100% cure rate with an 8% conversion rate to general anesthesia (16).

A decrease in operative time using sestamibi scanning has been suggested by Hindie et al. (20), who report a 30-min reduction in surgery time (from 120 to 90 min) since the introduction of sestamibi scanning at their institution. We found that scanning had no impact on operative time. Surgery on scanned patients lasted 40.2 min vs. 42.4 min on unscanned patients. Within the subgroup of scanned patients, surgery was 6 min faster in patients that had a positive scan compared with those that had a negative scan (P < 0.01).

Length of stay was not affected by the presence or absence of a preoperative sestamibi scan. All of the patients in each group had bilateral explorations under local anesthesia. This enabled 86% of the unscanned patients and 90% of the scanned patients (no significance) to be discharged to home from the recovery room within 6 h of completing the surgery. None of the ambulatory patients required readmission. The data in this series do not suffer from the variability of multiple practitioners because the outcomes reported are from the experience of a single surgeon (P.L.).

Previous authors have suggested that sestamibi scanning can identify ectopic glands and reduce surgical failure (17). The prevalence of undescended parathyroid glands is less than 1% but comprises 7–8% of patients who undergo reexploration (20). About 2% of abnormal parathyroid glands are located in the mediastinum and these ectopic glands account for 15–25% of unsuccessful surgery (20). In our series, four patients had mediastinal disease (0.8%). Thus, one ectopic mediastinal gland would be expected to be found out of every 125 sestamibi scans performed. However, even the preoperative identification of mediastinal disease would not rule out the possibility of multigland disease in the neck.

Eleven patients in this series were not cured by the initial exploration, only three of which were subsequently found to have mediastinal disease. One patient in the no scan group was not cured by initial transcervical exploration. Postoperative sestamibi scanning was negative. The patient then underwent a transthoracic thymectomy at another institution. No parathyroid adenoma was identified in the pathology specimen; however, postoperatively the patient’s PTH and serum calcium returned to normal. Two patients who had positive preoperative sestamibi scans were not cured at the initial exploration. One of these patients had a double adenoma that was a fifth gland in the mediastinum, which was removed transcervically at reexploration. The second patient remains uncured and has had no further intervention.

Eight patients with negative preoperative sestamibi scans were not cured by initial exploration. In two patients, there is no follow-up data. In the remaining six patients, although no parathyroid adenoma was found in the pathology specimen, all six patients had normal serum calcium levels by 3 months postoperatively. These patients either represent an error in the initial diagnosis, or may have had the blood supply to the adenoma interrupted during the exploration.

In this series, the incidence of hyperplasia is much lower and the incidence of double adenomas is much higher than most previously published reports. Initial concerns that some of the double adenoma patients actually had four gland hyperplasia is not supported by the surgical cure rate. It may be that the incidence of hyperplasia is decreasing due to less head and neck radiation (as a treatment for acne for example) or that our ability to diagnose familial benign hypocalcinuric hypercalcemia has improved.

While these results support the claim that the outcomes of experienced endocrine surgeons are not affected by scanning, preoperative localization studies may help surgeons with less experience. Ultrasonography will identify concomitant thyroid disease and may identify the adenoma, whereas a sestamibi scan will help to focus the surgeon’s attention on a specific site.

Most authors agree that a preoperative sestamibi scan is helpful in the recurrent or reoperative setting (17, 18). Localization studies enable taking a focused approach to identifying and removing the abnormal parathyroid gland. In our institution, sestamibi scans are usually obtained in patients with a history of previous surgery. At operation, a lateral approach is directed at the abnormal gland localized by sestamibi scan and only a unilateral exploration is performed if an abnormal gland is identified. This avoids the unnecessary risk to the recurrent laryngeal nerve to the contralateral side and permanent hypoparathyroidism. Others have suggested expanding this approach to initial neck explorations to decrease operative time and make the procedure amenable to local anesthesia (8). However, because of the lack of sensitivity and the high failure rate in patients with multigland disease, others feel that a unilateral exploration is not justified in this setting. Furthermore, a full neck exploration was performed under local/regional anesthesia in all of the patients in this series.

	Conclusion

Top Abstract Introduction Materials and Methods Results Discussion Conclusion References

 
In our prospective series of 525 consecutive neck explorations performed by a single surgeon for primary hyperparathyroidism, we found no benefit to preoperative sestamibi scanning in terms of surgical cure rate, mean operative time, or length of stay. All patients underwent a bilateral neck exploration under local/regional anesthesia, with most being done in an outpatient setting. Subgroup analysis demonstrated that patients with a negative preoperative sestamibi scan had a lower cure rate and slightly longer operative time when compared with patients with a positive scan. While this information may be helpful when counseling patients preoperatively, it has no bearing on our operative approach.

Received July 15, 2002.

Accepted January 23, 2003.

	References

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