CLINICAL TRIALS:

MYOCARDIAL IMAGING: In a trial of rest and stress Tc99m Sestamibi imaging, the relationship of normal or abnormal perfusion scans and long term cardiac events was evaluated in 521 patients (511 men, 10 women) with stable chest pain. There were 73.9% Caucasians, 25.9% Blacks and 0.2% Asians. The mean age was 59.6 years (range: 29 to 84 years). All patients had a baseline rest and exercise Tc99m Sestamibi scan and were followed for 13.2 ± 4.9 months (range: 1 to 24 months). Images were correlated with the occurrence of a cardiac event (cardiac death or non-fatal myocardial infarction). In this trial as summarized in Table 7.0, 24/521 (4.6%) had a cardiac event.

Although patients with normal images had a lower cardiac event rate than those with abnormal images, in all patients with abnormal images it was not possible to predict which patient would be likely to have further cardiac events; i.e., such individuals were not distinguishable from other patients with abnormal images.

The findings were not evaluated for defect location, disease duration, specific vessel involvement or intervening management.  


In earlier trials, using a template consisting of the anterior wall, inferior-posterior wall and isolated apex, localization in the anterior or inferior-posterior wall in patients with suspected angina or coronary artery disease was shown. Disease localization isolated to the apex has not been established. In adults, Tc99m Sestamibi has not been studied or evaluated in cardiac disorders other than coronary artery disease.  


BREAST IMAGING: Technetium Tc99m Sestamibi was evaluated in two multicenter, clinical trials of a total of 673 woman patients. Overall the mean age was 52 (range 23 to 87 years). The racial and ethnic representation was 70% Caucasian, 15% African-American, 14% Hispanic and 1% Asian.  


Both clinical studies evaluated women who were referred for further evaluation for either: 1) a mammographically detected (with varying degrees of malignant likelihood) but not palpable breast lesion (study A, n=387, mean age = 54 years), or 2) a palpable breast lesion (study B, n=286, mean age = 50 years). In both studies all patients were scheduled for biopsy.  


Technetium Tc99m Sestamibi (20-30 mCi) was injected intravenously in a vein that was contralateral to the breast lesion in question. Planar imaging was completed with a high resolution collimator with a 10% window centered at 140 KeV, and 128 x 128 matrix. An initial marker image, that was not used in the data analysis, was obtained using a cobalt Co57 point source as a marker of a palpable mass. Images were obtained 5 minutes after injection as follows: lateral image of the affected breast for 10 minutes, lateral image of the contralateral breast for 10 minutes, and an anterior image of both breasts for 10 minutes. For the lateral image the patients were positioned in a prone position. For the anterior image, the patients were supine. The Technetium Tc99m Sestamibi scintigraphic images were read in a randomized method by two groups of three blinded readers. Technetium Tc99m Sestamibi uptake was scored as: normal (no uptake), equivocal, low, moderate, or high uptake. The results of Technetium Tc99m Sestamibi images and mammography were analyzed in comparison to histopathologic findings of malignant or non-malignant disease.  


As shown in Table 8.0 for the 483 evaluable patients, the sensitivity and specificity of any degree of Technetium Tc99m Sestamibi uptake appear to vary with the presence or absence of palpable mass.

In separate retrospective subset analyses of 259 patients with dense (heterogeneously/extremely dense) and 275 patients with fatty (almost entirely fat/numerous vague densities) breast tissue, the Technetium Tc99m Sestamibi results were similar. Overall, the studies were not designed to compare the performance of Technetium Tc99m Sestamibi with the performance of mammography in patients with breast densities or other coexistent breast tissue disorders.

In general the histology seems to correlate with the degree of Technetium Tc99m Sestamibi uptake. As shown in Tables 9.0 and 10.0, the majority of the normal Technetium Tc99m Sestamibi images are associated with non-malignant tissue (78-81%) and the majority of low, moderate or high uptake Technetium Tc99m Sestamibi images are associated with malignant disease (79-83%). In an individual patient, however, the intensity of Technetium Tc99m Sestamibi uptake can not be used to confirm the presence or absence of malignancy. Equivocal results do not have a correlation with histology.

An estimate of the likelihood of malignancy based on the Technetium Tc99m Sestamibi uptake score in combination with the mammographic score has not been studied.

In these two studies approximately 150 additional, non-biopsied lesions were found to be positive after Technetium Tc99m Sestamibi imaging. These lesions were identified in sites that did not physically correlate with identified entry criteria mammographic lesions and these lesions were not palpable. These lesions were not biopsied. Whether these lesions were benign or malignant is not known. Technetium Tc99m Sestamibi uptake can occur in both benign and malignant disease. THE CLINICAL USEFULNESS OF A POSITIVE Technetium Tc99m Sestamibi IMAGE IN THE ABSENCE OF AN ABNORMAL MAMMOGRAM OR A PALPABLE LESION IS NOT KNOWN.