Retention Index of Tc-99m MIBI Thyroid Scintigraphy, Ultrasonography, and Fine-Needle Aspiration Cytology in the Assessment of Thyroid Nodule Ivana D. Mulyanto1, Basuki Hidayat1, Dimyati Achmad2, A. Hussein S.Kartamihardja1, Johan S. Masjhur1 Department of Nuclear Medicine1, Department of Oncological Surgery2 Universitas Padjadjaran - Dr. Hasan Sadikin Hospital Bandung, Indonesia

BACKGROUND US  19 – 67% Palpable  5% woman and 1% man P R E V A L N *Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer.Thyroid 2009;19:1167 – 8

BACKGROUND Thyroid nodule Thyroid cancer: Benign lesion: 85– 95% 5 – 15% Benign lesion: 85– 95% Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer.Thyroid 2009;19:1167–8 Schlumberger M., Pacini F. Thyroid tumor 3th ed. Thyroid Nodule. Paris 2006:13–14

Non invasive preoperative diagnostic modalities BACKGROUND Size, echogenicity, shape, margin, echostructure, calcification Operator dependent I-123, I-131, Tc-99m pertechnetate Cold nodule: 5-15% malignant FNAC  15-30% indeterminate result Non invasive preoperative diagnostic modalities

Tc-99m-hexakis-2-methoxyisobuthylisonitrile (Tc-99m MIBI) Negative potential membrane HIGH UPTAKE & RETENTION High number and activity of mitochondria High number and activity of mitochondria Malignant thyroid nodule Malignant cell Rodrigues M, Chehne F, Kalinowska W, Berghammer P, Zielinski C, Sinzinger H. Uptake of 99mTc-MIBI and 99mTc-Tetrofosmin into malignant versus nonmalignant breast cell lines. J Nucl Med 2000; 41: 1495-9 Carew JS, Huang P. Mitochondrial defects in cancer. Mol Cancer 2002; 1: 9

OBJECTIVE This prospective study was designed to assess the significance of Tc-99m MIBI thyroid scintigraphy using retention index(RI) parameter, ultrasound(US), and fine-needle aspiration cytology(FNAC) in differetiating benign from malignant thyroid nodule.

Material & Method Inclusion criteria: Patients with palpable single thyroid nodule US Tc-99m MIBI thyroid scintigraphy FNAC Surgery Inclusion criteria: cold nodule on Tc-99m pertechnetate thyroid scan; normal serum TSH and thyroid hormone level Kang score ≤2  benign Kang score >2  malignant Dual phase acquisition with semiquantitative analysis Benign : coloid goitre, thyroiditis Indeterminate : follicular neoplasm Malignant : papillary thyroid ca Lobectomy, isthmolobectomy, or total thyroidectomy

RESULT

Histopathological finding RESULT RI of Tc-99m MIBI Histopathological finding p value Malignant Benign Mean(SD) 1.04(0.50) 0.58(0.17) 0.0015

RESULT Cut-off point: >0.58 Sensitivity : 87.5% Specificity : 70.6% PPV : 58.3% NPV : 92.3% Accuracy : 76% (95%CI: 47.3-99.7; LR: 2.98)

Histopathological finding RESULT US Histopathological finding Total p value Malignant Benign Kang score >2 7 (87.5%) 8 (47.1%) 15 Kang score ≤2 1 (12.5%) 9 (52.9%) 10 8 17 25 0.065 Sensitivity 87.5%; specificity 52.9%; PPV 46.7%; NPV 90%; accuracy 64%

Histopathological finding RESULT FNAC Histopathological finding Total p value Malignant Benign 5 Indeterminate 2 4 6 1 13 14 8 17 25 0.001 Sensitivity 62.5%; specificity 76.5%; PPV 55.5%; NPV 81.3%; accuracy 72% Indeterminate results (n=6): - 2 (33.3%)  malignant (follicular thyroid ca) - 4 (66.6%)  jinak (follicular adenoma) Tc-99m MIBI RI diagnosed 5 of 6 subjects (83.3%) with indeterminate result

Tc-99m MIBI Thyroid Scintigraphy RESULT Tc-99m MIBI Thyroid Scintigraphy US FNAC Sensitivity 87.5% 62.5% Specificity 70.6% 52.9% 76.5% NPV 92.3% 90% 81.3% PPV 58.3% 46.7% 55.5% Accuracy 76% 64% 72% Kappa Index 0.51 0.38 0.33

? Size Vascular supply Proliferation rate Discussion One subject with Tc-99m MIBI RI of 0.39 showed malignant histopathological finding. Five subjects with Tc-99m MIBI RI of 0.68 – 0.93 showed benign histopathological finding. Size Vascular supply Proliferation rate ?

CONCLUSION RI of Tc-99m MIBI thyroid scintigraphy may be useful in the assessment of thyroid nodule, for it has high negative predictive value and agreement compared to histopathological result.

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