Comparison between 99mTc-sestamibi scintimammography and X-ray mammography in the characterization of clusters of...

The early diagnosis of non-palpable breast cancer is the object of recent developments in the imaging procedures employed for screening purposes. In some patients, the presence of microcalcifications (MC) is the only indication of tumor. Although X-ray mammography (MRx) has high sensitivity in detecting MC, its specificity is however too low for diagnostic purposes. The aim of this study was to compare (99m)Tc-sestamibi scintimammography (SMM) and MRx in the differential diagnosis between benign and malignant clusters of MC and to assess the possible incremental value of SMM on specificity.

A total of 283 consecutive women (mean age 53+/-8 years) with MC identified on X-ray mammograms underwent SMM. Scintigraphic images were acquired 10 minutes after the i.v. injection of (99m)Tc-sestamibi (740 MBq). Planar images of both breasts were simultaneously obtained in the lateral prone position and in the anterior and oblique projections using a dual head camera. Sixty-nine women underwent surgery, whereas the remaining 214 patients had completely negative follow-up for 5 years (a 5-year follow-up period is considered the "gold standard" for diagnosing benign lesions).

Histology demonstrated 32/69 primary breast carcinomas (prevalence of disease: 11% of all the 283 patients) and 37/69 benign lesions. The receiver operating characteristic (ROC) statistical technique was employed to compare the diagnostic value of Mrx alone to that of combined MRx and SMM. The detected difference between the areas under the MRx ROC curve (area=0.72, standard error 0.052) and the MRX and SMM ROC curve (area=0.86, standard error 0.039) was statistically significant (p<0.01). Moreover, the combination of MRx and SMM provided a significant improvement of the negative predictive value (NPV=98%) for MC with low-suspicion of malignancy at MRx.

SMM can be considered as a complementary tool in the pre-operative work-up of patients with breast lesions. Furthermore, the high negative predictive value of this technique, makes it especially valuable in the perspective of reducing the number of negative breast biopsies or unnecessary surgical interventions.