MON-LB088 Comparative Study of Single Photon Emission Computed Tomography (SPECT)/CT Imaging Versus Combined Planar Technetium-99m Sestamibi -Ultrasonographic Imaging for Pre-Operative Parathyroid Localisation in Primary Hyperparathyroidism.

Primary hyperparathyroidism is the third most common endocrine disorder in the western world with an estimated prevalence of 1-4 per 1000.The only curative treatment is surgical resection. Minimally invasive surgical techniques are preferred over bilateral neck exploration due to reduced risk of surgical complications (1.2% vs 3%) and seven-fold shorter hospital stay with cost reduction of up to 50% (1); however this requires accurate preoperative localisation. Various imaging modalities evolved over time to identify pathological parathyroid glands pre-operatively. Imaging modality which is non-invasive, accurate and has minimal radiation exposure should be preferred as a first line option. Planar Technetium-99m Sestamibi scintigraphy coupled with Ultrasonography (MIBI/USS) has conventionally been used as the localisation study of choice. Single Photon Emission Computed Tomography (SPECT)/CT has been introduced recently and adopted by our centre as a first line investigation. The aim of the current study was to compare the accuracy of MIBI/USS versus SPECT/CT in localising pathological parathyroid glands preoperatively and assess the influence of imaging modality on surgical outcomes. A total of 135 patients with confirmed primary hyperparathyroidism were studied retrospectively in a tertiary centre over 24 months period. 61 patients underwent MIBI/USS and 74 had SPECT/CT as first line imaging. 82% of patients were female with mean age of 67 years. Preoperatively Sestamibi -SPECT/CT identified the laterality of the adenoma in 78.4% of cases, compared to 49.2% in MIBI/USS (p<0.001). Post operative surgical and histological concordance in terms of laterality and position (inferior or superior) of the hyper-functioning gland SPECT/CT (59.5%) was still superior compared to MIBI/USS (34.4%), p=0.04. There were two cases of intra-thyroidal adenoma of which both were identified by SPECT/CT. Additionally there were two cases of mediastinal parathyroid foci identified on SPECT/CT. None of the patients who underwent MIBI/USS had ectopic foci. Out of the 135 patients, 83.0% had a single parathyroid adenoma, 9.6% had single or multi-gland hyperplasia, 1.4% had ectopic parathyroid adenomas (n=1 mediastinal, n=1 thymus) and there were no cases of parathyroid carcinoma. 16 patients (22.5%) in the SPECT/CT group had bilateral neck exploration versus 24 (39.3%) in the MIBI/USS group (p = 0.04).There was no difference in length of hospital stay (average 1 day) between groups and no significant difference in post operative complications (laryngeal nerve palsy, post-operative hypocalcaemia) between the two groups . There was no statistically significant difference between cure rates with either modality of imaging MIBI/USS or SPECT/CT (93.4% and 93.1% respectively, p=0.93) (1).R.UDELSMAN. 656 consecutive explorations for primary hyperparathyroidism. Ann Surg. 2002;235(5):665-70 Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.