99MTC [13LEU] bombesin and a new gamma camera, the imaging probe, are able to guide mammotome breast biopsy

A pilot study has been carried out in order to verify the feasibility of scintigraphic driving for breast biopsy. A new high resolution (HR) gamma ray detector, the imaging probe (IP), and 99mTc [13Leu] Bombesin (99mTc BN), have been used to drive a mammotome biopsy needle after having fused radioisotope with digital X-ray images. IP is a mobile, high resolution, miniaturised gamma camera, whose field of view is one inch and whose spatial resolution is 2 mm. 99mTc BN is a new radiotracer derived from the well-known peptide, that has already shown very high sensitivity in detecting breast cancer.

Five patients very suspicious for breast cancer were studied. 185 MBq of 99mTc BN were i.v. injected and dynamic prone scintimammography was performed for 20 minutes with a conventional large field of view gamma camera. IP was matched with the biopsy system and digital X-ray device of a mammotome system, in order to fuse images and to use the mammotome pointer indifferently on X-ray, scintigraphic and fused images. Biopsy samples were counted and weighed: uptake was expressed as counts sec-1 gr-1. Samples were classified into high, intermediate and low uptake. Conventional histological assessment was blindly performed on the samples.

All of the patients showed cancer. The T categorisation was T1a for two cancers and T1b for 3. Dynamic prone scintimammography with conventional gamma camera, as well as HR scintigraphy with IP showed spots of 99mTc BN uptake. Maximal mismatch between X-ray lesions and of hot spots imaged with IP before mammotome scintigraphy was 3.4 mm. All the high uptake samples and all but two of the intermediate uptake samples showed cancer, whereas histology found malignant tissue in only 2 out of the 8 low uptake samples.

99mTc BN confirms its high sensitivity in detecting breast cancer. IP is able to drive or co-drive breast biopsy when used with appropriate radiopharmaceuticals.