Renal Kitle Değerlendirilmesinde Tc-99m Mibi Tümör Sintigrafisinin Rolü: Gerçek Fayda Var Mı?
Özet
Objective: The role of Tc-99m methoxy isobutyl-isonitrile (MİBİ) tumor scintigraphy in the differentiation of benign and malignant renal masses is still controversial. We sought to demonstrate the efficacy of Tc-99m MİBİ tumor scintigraphy in clinical decision making by comparing preoperative Tc-99m MİBİ tumor scintigraphy findings with postoperative pathologic results.
Method and Material: Between July 2017 and March 2019, 86 patients presenting with clinical T1 renal mass underwent preoperative 99mTc-sestamibi tumor scintigraphy. Images were evaluated by plotting the area of interest of radioactive material in renal masses and proportioning it to normal renal parenchyma. Lesion-to- normal kidney ratios (L/K) were calculated to determine the relative uptake of the lesion. Immunohistochemical studies were conducted to determine MDR1 pump expression in the excised lesions. The preoperative Tc-99m sestamibi tumor scintigraphy findings were compared with the postoperative pathology results.
Results: A total of 86 patients with 90 renal masses were included in the study. Male to female ratio was 67/23. The mean age and tumor size were 55.5 ± 11.2 years and 4.1 ± 1.4 cm, respectively. 46.7% of all masses were larger than 4 cm. 77.8% and 22.2% of patients underwent partial and radical nephrectomy, respectively. In pathological evaluation, 18 (20.0%) of the 90 excised masses were reported as benign (10 oncocytomas, 4 angiomyolipomas (AML), 2 chronic sclerosis, 1 fibroma and 1 hydatid cyst).
The mean Tc-99m MİBİ lesion / normal renal parenchyma ratio of benign lesions was 0.6. Using the ideal threshold value of 0.49 which was calculated using ROC curves, the sensitivity was 90%. While Tc-99m sestamibi uptake was positive in all oncocytomas; 6 patients with chronic sclerosis, fibroma, hydatid cyst and anjiomyolipoma pathologies had no uptake.
The mean Tc-99m MİBİ lesion / normal renal parenchyma ratio of the 72 malign lesionswas 0.37. Using the ideal threshold value, the specifity was 80%. 5 chromophobe cell RCC and 3 oncocytic papillary RCC masses had positive Tc-99m sestamibi uptake (lesion / normal renal parenchyma 0.6).
In predicting benign pathology, Tc-99m sestamibi tumor scintigraphy had positive and negative predictive value of 60% and 91.3%, respectively. Average relative uptake of 0.5 was an acceptable cutoff point to discriminate oncocytomas from all other pathologies. MDR1 pomp expression was less in benign lesions.
Conclusion: In the assessment of renal mass, Tc-99m sestamibi tumor scintigraphy has clear benefits in clinical decision making. Masses with negative uptake harbor high probability of being malignant. While evaluating masses with positive uptake, it should be kept in mind that some malignant pathologies may demonstrate similar results. Fortunately, these malignant pathologies have relatively better prognosis.
