Improving the yield of preoperative parathyroid localization: technetium Tc 99m-sestamibi imaging after thyroid suppression

Does levothyroxine administration impact parathyroid localization?

BACKGROUND

Proper localization is crucial in performing minimally invasive parathyroidectomy for primary hyperparathyroidism. Ultrasonography (US) and Tc-99m sestamibi (MIBI) scintigraphy are common methods used for localization. As the appearance and activity of the thyroid gland may impact parathyroid localization, the purpose of this study was to determine how exogenous use of the thyroid hormone, levothyroxine (LT), affects parathyroid localization.

METHODS

Adult patients with non-familial primary hyperparathyroidism who underwent initial parathyroidectomy from 2000-2014 were retrospectively identified. LT (+LT) and non-LT (-LT) patients were matched 1:3 based on age, gender, goiter status, and preoperative parathyroid hormone levels. Subgroup analysis was performed on patients previously treated with radioactive iodine and patients undergoing single adenoma resection.

RESULTS

Of the 1737 patients that met inclusion criteria, 286 were on LT at the time of their parathyroid localization scan. Use of LT did not impact the percentage of correct MIBI localization scans when compared with -LT patients (P = 0.83). Interestingly, use of LT significantly hindered localization by US in comparison with the -LT group (48.4 versus 62.2%, P < 0.01). When examining only patients where a single upper gland was removed, the +LT group was less likely to have a correct US compared with the -LT group (50 versus 72.8%, P < 0.01). However, there was no difference in US accuracy for patients who only had a single lower gland removed (P = 0.51).

CONCLUSIONS

Exogenous LT is associated with impaired parathyroid localization with US but not MIBI. Surgeons should be aware of localization efficiency for this subset of patients in the era of personalized medicine and cost effectiveness.

Radiographic evaluation of non-localizing parathyroid adenomas

PURPOSE

Patients with primary hyperparathyroidism routinely undergo preoperative imaging to localize the abnormal gland to facilitate a guided parathyroidectomy. These techniques include neck ultrasound (US), dual phase planar technetium-99m ((99m)TC) sestamibi (MIBI) scans, single photon emission computed tomography (SPECT), combined SPECT/CT, and four dimensional CT scans (4D CT). Despite appropriate preoperative imaging, non-localization of abnormal glands does occur. This study aims to determine whether non-localization is the result of radiologic interpretive error or a representation of a subset of truly non-localizing parathyroid adenomas.

MATERIALS AND METHODS

A retrospective study was performed; two senior radiologists reinterpreted the preoperative imaging (US and MIBI scans) of 30 patients with initially non-localizing studies. All patients underwent parathyroidectomy for primary hyperparathyroidism at a tertiary referral center. Both radiologists were blinded to the scores of his colleague. The results were compared for inter-reader reliability using Cohen's kappa test.

RESULTS

Twenty-nine of thirty nuclear studies were found to be negative on reinterpretation. The readers agreed in 86.67% of their observations, with a kappa (κ) value of 0.706 (SE=±0.131, 95% confidence interval for κ =0.449-0.962). One of eighteen ultrasounds had positive localizations on reexamination, however, the inter-observer agreement was only 55.6%, with a kappa value of 0.351 (SE=±0.139, and 95% confidence interval for κ =0.080-0.623). Overall, no statistically significant difference in preoperative and retrospective interpretation was found.

CONCLUSION

This study identifies a subset of parathyroid adenomas that do not localize on preoperative imaging despite sound radiographic evaluation.

[Thyroid suppression in patients with primary hyperparathyroidism: does it improve the pre-surgical scintigraphy localisation?]

INTRODUCTION

Scintigraphy with technetium-sestamibi (MIBI) is the test of choice for localising adenomas in patients with primary hyperparathyroidism (PHPT). In some studies it has emerged that the increase in sensitivity of this test could be associated with a decrease in the uptake of the radiotracer by the thyroid gland. The aim of this study is to analyse our experience in patients with a negative scintigraphy with MIBI, and in whom the study was repeated after suppression of thyroid function with thyroxine.

MATERIAL AND METHODS

A prospective evaluation was performed on 17 patients who, between January 2006 and April 2011, had PHPT and negative imaging using scintigraphy with MIBI and who had the test repeated after the administration of thyroxine. The scintigraphy data and the correlation with the findings in the surgical intervention are reviewed.

RESULTS

The mean TSH at the time of repeating the MIBI was 0.12+0.1mlU/L. Of the 17 patients included, the scintigraphy under thyroid suppression was positive in 13 of them (76.5%), and in the other 4 (23.5%) patients no image suggestive of adenoma was found. In the cases where the MIBI was positive after suppression, the positive predictive value (PPV) was 100%.

CONCLUSION

Suppression of thyroid function by giving thyroxine can help to improve the sensitivity of MIBI in patients with previously negative scintigraphy studies and help in the minimally invasive treatment of patients with PHPT.

Imaging of parathyroid glands

Preoperative imaging studies have an important role in facilitating successful localization of adenomas for surgeons. Their use has increased and parallels the recent growth of minimally invasive parathyroidectomy. Based on findings that scintigraphy is reported to have the highest accuracy for localization of adenomas when compared with anatomic imaging techniques, this article discusses the current role and limitations of imaging, with a focus on scintigraphy, in the evaluation of patients before surgery for hyperparathyroidism.

Determinants of Tc-99m sestamibi SPECT scan sensitivity in primary hyperparathyroidism

BACKGROUND

The aim of this study was to evaluate the influence of patient and adenoma characteristics on (99m)Tc-methoxy isobutyl isonitrile (MIBI) scan performance in individuals diagnosed with primary hyperparathyroidism (PHP).

METHODS

Records of patients undergoing parathyroidectomy for PHP over 6 years at a single center were reviewed.

RESULTS

The overall true-positive (TP) rate for (99m)Tc-MIBI scans was 56%. Adenomas sized 1.9 to 3.5 cm were more likely to have TP scans than 0.3-cm to 1.8-cm adenomas (74% vs 40%, P < .001). Preoperative ionized calcium levels between 1.49 and 1.72 mmol/L were more likely to have TPs than levels between 1.27 and 1.48 mmol/L (65% vs 47%, P < .05). No single class of medication was shown to significantly effect TP rates. A decrease in TP rate was observed for larger adenomas in patients on >or=1 medication (74% vs 65%, P = .05).

CONCLUSIONS

In PHP, (99m)Tc-MIBI scan positivity is most related to adenoma size and preoperative ionized calcium level.

Two-phase scintigraphy with technetium 99m–sestamibi in patients with hyperparathyroidism due to chronic renal failure

BACKGROUND

The objective of the current study was to study different functional and anatomic features of the hyperplastic gland and clinical and biochemical characteristics of renal hyperparathyroidism (HPT) patients and their relationship with the scintigraphic detection of parathyroid glands.

METHODS

A retrospective study was performed of 40 patients with chronic renal failure (CRF) who underwent cervical surgery for HPT. Weight, histology, and localization of hyperplastic glands were recorded. Parathyroid cell proliferation was assessed by percentage of S-phase cells. Double-phase scintigraphy with technetium 99m-sestamibi and serum parathyroid intact hormone (PTHi), creatinine, calcium, and phosphate levels were performed.

RESULTS

Detection of hyperplastic parathyroid glands by 99mTc-sestamibi scintigraphy was associated with the weight and inferior localization of the glands. The functionality of the glands as reflected in serum PTHi and phosphorus levels was associated with the number of glands detected.

CONCLUSION

Double-phase 99mTc-sestamibi scintigraphy is of limited usefulness in patients with renal HPT. Detection of hyperplastic parathyroid glands in patients with CRF depends on the weight and inferior localization of the glands. Serum PTHi, phosphorus and creatine levels are associated with the number of glands detected by means of 99mTc-sestamibi scintigraphy.

Radionuclide imaging for hyperparathyroidism (HPT): which is the best technetium-99m sestamibi modality?

BACKGROUND

To determine the utility of available radionuclide imaging modalities for preoperative parathyroid localization, we compared the accuracy of 4 types of technetium-99m ((99)Tc) sestamibi-based scans.

METHODS

Over 5 years, 833 patients with sporadic primary hyperparathyroidism underwent either (99)Tc-sestamibi with planar views (Planar; n = 138); sestamibi single photon emission computed tomography (SPECT; n = 165); SPECT with thyroid (123)I-subtraction phase (SPECT/(123)I; n = 350); or SPECT combined with conventional CT (SPECT/CT; n = 180). The accuracy of each modality was determined on the basis of intraoperative parathyroid pathology, defined as single adenoma or multigland disease.

RESULTS

Planar scans had significantly more false negatives (no tumor visualized) than SPECT-based scans (P < 0.01), but positive predictive values were similar. A false-negative scan was present in 38% of Planar scans, 27% SPECT, 4% SPECT/(123)I, and 17% SPECT/CT, with single adenoma found at operation in 77%, 64%, 53%, and 74%, respectively. When a scan had a single focus of uptake, SA was found at that location in 77%, 85%, 68%, and 87%, respectively. SPECT, SPECT/(123)I, and SPECT/CT did not significantly reduce the false-positive rate.

CONCLUSIONS

We recommend obtaining multiplanar SPECT-based imaging, which offers 3-dimensional localization and improved detection of parathyroid tumors when compared with Planar scans. A negative scan did not predict multigland disease.

How to localize parathyroid tumors in primary hyperparathyroidism?

The management of primary hyperparathyroidism (PHPT) has dramatically changed in the last 5 yr. Many more patients now undergo focused, limited or minimally invasive parathyroidectomy instead of traditional bilateral neck exploration. This change has taken place because of the improved accuracy of pre-operative localizing studies in selecting patients who have single-gland parathyroid disease (single adenoma) and can therefore have a minimally invasive parathyroidectomy. Sestamibi scanning followed by ultrasound, magnetic resonance imaging (MRI) and computed tomography (CT) scans are most accurate for localizing parathyroid tumors in patients with PHPT. Selective venous catheterization for PTH levels is useful when other localizing studies are negative or discordant in patients with persistent or recurrent PHPT. The routine use of one or more localizing studies commonly identifies the parathyroid tumor in patients with single-gland disease; but if localizing studies are negative or discordant, patients should have intra-operative PTH levels monitored or have a bilateral neck exploration to ensure a high rate of biochemical cure.

What is the link between nonlocalizing sestamibi scans, multigland disease, and persistent hypercalcemia? A study of 401 consecutive patients undergoing parathyroidectomy

BACKGROUND

We hypothesized that nonlocalizing sestamibi scans would correlate with multigland disease and persistent primary hyperparathyroidism.

METHODS

We reviewed records for 401 consecutive patients who underwent parathyroidectomy from 1999 to 2004. Gender, age, preoperative imaging, surgical findings, gland weight and volume, and 6-month calcium levels (Ca) were examined.

RESULTS

We identified 289 women and 112 men, 297 of whom had a preoperative sestamibi scan localized to a single gland (localized group; LG). Ninety-six percent of the LG were found to have single-gland disease, and 4% had multigland disease (MGD). In the nonlocalized group (NLG), 76% had single-gland disease and 24% MGD. Mean gland weight was greater in the LG than in the NLG (1128 mg vs 699 mg; P < .05). Mean gland volume was larger in the LG (1.34 cc vs 0.89 cc; P < .05). A localizing sestamibi scan had a positive predictive value (PPV) of 96% and a likelihood ratio of 2.29 for predicting "curative" intraoperative parathyroid hormone drop after removal of a single abnormal gland. Patients were stratified into normocalcemic (NCa) and hypercalcemic (HCa) groups based on 6-month postoperative serum calcium data (n = 328). HCa incidence at 6 months did not differ significantly between the LG (5%) and NLG (3%). A localizing scan had a PPV of 95% for normocalcemia at 6 months. A nonlocalizing scan had a PPV of 21% for HCa at 6 months.

CONCLUSIONS

Nonlocalizing sestamibi scans were more common in primary hyperparathyroidism with MGD and were associated with smaller-volume abnormal glands found at operation. Preoperative sestamibi scan-results did not predict HCa at 6 months.

Negative Imaging Studies for Primary Hyperparathyroidism Are Unavoidable: Correlation of Sestamibi and High-Resolution Ultrasound Scanning with Histological Analysis in 150 Patients

BACKGROUND

Preoperative localization studies with Tc99m-sestamibi have become an integral step in the preoperative assessment of patients with primary hyperparathyroidism (PHPT). This enables scan-directed minimally invasive parathyroidectomy (MIP) to be the preferred treatment for PHPT in many units. This study aimed to identify factors that lead to negative imaging studies in patients with PHPT.

METHODS

Over a 3-year period consecutive unselected patients with PHPT underwent Tc99m-sestamibi scanning and high-resolution ultrasound (US) scanning by the same radiologist. When localization studies were concordant, patients underwent MIP. Those patients with negative imaging studies underwent bilateral neck exploration. Histology slides were independently reviewed and the proportion of chief cells and oxyphil cells within each adenoma was estimated.

RESULTS

One hundred and fifty-eight patients underwent localization studies (38 men and 120 women, aged 61.8 +/- 15.2 years). Sestamibi scans were negative in 52 (32%) and positive in 106 (68%) patients. There was a higher incidence of hyperplasia in the group of patients with negative sestamibi scans (4 out of 52 vs. 4 out of 103, P < 0.05, chi2 test). In patients with negative sestamibi scans the majority of adenomas were formed predominantly from chief cells (26 out of 36) while the majority of patients with adenomas composed predominantly of oxyphil cells had positive scans (21 out of 23) (P < 0.05, chi2 test). The weight of parathyroid adenomas was higher when sestamibi scans were positive (median: 1,180 vs. 517 mg, P < 0.05, Student's t-test).

CONCLUSION

Successful preoperative localization of parathyroid adenomas using Tc99m-sestamibi scanning is influenced by the cytological predominance of individual tumors. Negative scans might therefore be unavoidable in a subgroup of patients.

Effect of calcium channel blockers on the sensitivity of preoperative 99mTc-MIBI SPECT for hyperparathyroidism

BACKGROUND

Technetium 99m ( 99m Tc)-methoxyisobutylisonitrile (MIBI) single photon emission computed tomography (SPECT) is frequently used in the evaluation of patients with hyperparathyroidism. Calcium channel blockers (CACBs) may affect 99m Tc-MIBI uptake by parathyroid cells. This study examines the effect of CACB therapy on the sensitivity of 99m Tc-MIBI SPECT localization for hyperparathyroidism.

METHODS

Two hundred fifty-three operated patients with hyperparathyroidism were retrospectively reviewed. The potential effect of CACB therapy on 99m Tc-MIBI scan sensitivity was examined by using logistic regression analysis. Possible confounding factors were considered.

RESULTS

Among 235 patients, those with multiple endocrine neoplasia, type I (MEN-I), MEN-IIA, 4-gland hyperplasia, secondary hyperparathyroidism, and tertiary hyperparathyroidism exhibited no difference associated with CACB use. Of the remaining 198 patients with primary hyperparathyroidism, 7/30 (23%) with negative 99m Tc-MIBI SPECT scans compared to 24/168 (14%) with positive scans used CACBs. After correcting for age, gender and gland weight, the odds ratio (OR) for a negative study in patients taking CACBs was 2.88 (95% CI, 1.03-8.10; P = .045). Atherosclerosis, hypertension, diabetes mellitus, preoperative calcium and parathyroid hormone levels, and thyroid hormone use were not confounding factors.

CONCLUSIONS

CACB therapy reduces the sensitivity of 99m Tc-MIBI parathyroid SPECT in patients with primary hyperparathyroidism. Further studies are required to determine the potential reversibility of this effect with termination of CACB therapy.

Technetium-99m 2-Methoxyisobutyl isonitrile-scintigraphy: Preoperative and Intraoperative Guidance for Primary Hyperparathyroidism

As refinement of technetium-99m 2-methoxyisobutyl isonitrile-scintigraphy (MIBI)-scintigraphy of parathyroid glands has continued since its initial use in 1989, the sensitivity, specificity, and overall accuracy of the technique have improved greatly, approaching 100% for larger, solitary adenomas. Preoperative use of sestamibi scintigraphy has become commonplace and allows surgeons the option of a minimally invasive, or focused approach for their patients with primary hyperparathyroidism. Intraoperative use of the gamma probe based on sestamibi localization has not caught on due to lesser accuracy, cumbersome gamma probes, small doses of radiation exposure for patients and staff, and the greater accuracy and current confidence in intraoperative parathormone (PTH) monitoring. However, with the potential for smaller and more accurate gamma probes that truly assist in localizing abnormal parathyroid glands, the potential for cost reduction by shortening operative times, avoiding expensive PTH assays, and eliminating the need for pathologic analysis, gamma scintigraphy may yet become a viable option for many parathyroid surgeons.

[Primary hyperparathyroidism: parathyroid scintigraphy and ultrasound in problem patients]

AIM

In a retrospective study, the sensitivity of parathyroid scintigraphy and ultrasound was investigated in patients with primary hyperparathyroidism (HPT) with prior histories of surgery of the thyroid or parathyroid (unsuccessful or recidive).

METHODS

Preoperative ultrasound and parathyroid scintigraphy were performed on 65 patients who had had successful surgery and on 12 who had had unsuccessful surgery. The scintigraphy was carried out using a combined double phase/double nuclide technique with 300-600 MBq 99mTc-sestamibi for parathyroid imaging and 80-100 MBq 99mTc-pertechnetate for thyroid imaging.

RESULTS

The sensitivity of parathyroid scintigraphy was 86% in patients with normal thyroid glands, 77% in those with recurrent goiter, and 62% in those with recurrent or persistent HPT. The ultrasound sensitivity was 86%, 50%, and 57% respectively.

CONCLUSION

The sensitivity of parathyroid scintigraphy and ultrasound decreases considerably after surgery. That of parathyroid scintigraphy lay significantly below results published to date. However, parathyroid scintigraphy should be performed precisely in these cases, because the number of alternative parathyroid imaging methods aside from ultrasound are limited.