The usefulness of 99mTc-tetrofosmin SPECT scintimammography in the detection of small size primary breast carcinomas

The aim of this study was to evaluate the usefulness of supine 99mTc-tetrofosmin SPECT in the detection of small size breast carcinomas (BC), for which planar scintimammography has showed a low sensitivity. We studied 93 patients with breast lesions ≤10 mm, 69 with BC (14 T1a and 55 T1b, 39 palpable and 30 non-palpable) and 24 with benign lesions (16 palpable and 8 non-palpable). All patients had previously undergone clinical examination and mammography. Ten min after 740 MBq 99mTc-tetrofosmin i.v. injection, both planar and SPECT (360°; angular step: 3°; acquisition time/frame: 30 sec) scintimammography were performed in all patients using a rectangular dual head gamma camera equipped with HR parallel-hole collimators. In all patients the scintigraphic data were related to histology. In the 69 BC patients, SPECT showed a significantly higher overall sensitivity than planar (89.8% vs. 46.4%; p<0.0005). SPECT gave a higher sensitivity than planar in both T1a (71.4% vs. 35.7%) and T1b (94.5% vs. 49.1%) carcinomas, and in the latter the difference was statistically significant (p<0.0005). SPECT sensitivity was also significantly higher in palpable (94.9% vs. 48.7%; p<0.0005) and non-palpable (83.3% vs. 43.3%; p<0.005) carcinomas. SPECT and planar imaging showed the same specificity (95.8%). SPECT showed a significantly higher overall negative predictive value and accuracy than planar (76.7% vs. 38.3% and 91.4% vs. 59.1%, respectively; p<0.0005). In our series mammography sensitivity, specificity and accuracy were 94, 36.8 and 81.4%, respectively. 99mTc-tetrofosmin SPECT is a widely available diagnostic method and appears highly accurate in the detection of small size BC, improving the low sensitivity of planar scintimammography. In particular, SPECT seems indicated for T1b carcinoma detection, although its usefulness in T1a carcinomas should not be ignored. A larger clinical application of SPECT as complementary tool to mammography is suggested in small size primary BC diagnosis.