Technetium labeled bombesin-like peptide: Preliminary report on breast cancer uptake in patients

Bombesin-like peptides are neurotransmitters and cancer growth factors. Several tumors, breast cancer among them, show one or more than one of the three known bombesin receptors. We have synthesized and labeled with technetium 99m a new pentadecapeptide, analogue to the leu(13) amphibian bombesin (Tc-99m BN). Labeling yield was 83 +/- 4%. Prone Scintimammography was performed on five patients affected by breast cancers (T categorization: two T1b and three T1c), after injecting 0.7 mg, 185 to 296 MBq (5 to 8 mCi) of the peptide. Total body scan did not show free technetium biodistribution. No adverse reaction was observed. Prone Scintimammography with Tc-99m Sestamibi (Tc-99m SM) was also performed few days later. Tc-99m BN detected all 5 cancers, whereas Tc-99m SM only four: all the T1c and one T1b cancer. Two of them showed axillary node invasion that was detected by both the radiotracers. A fibroadenoma present on contralateral breast to the one with cancer, was not detected neither-by Tc-99m SM nor by Tc-99m BN. Tumor/breast normal tissue ratio (T/B) was constantly higher with Tc-99m BN than with Tc-99m SM. Maximal T/B was measured as 1.79 with Tc-99m SM and 2.25 with Tc-99m BN 5 min after fast i.v. administration. In conclusion our Tc-99m BN is taken up by primary breast cancer showing higher T/B than Tc-99m SM (p < 0.01). In our limited scale, Tc-99m BN appears to be safe and, in our limited scale, even more accurate than Tc-99m SM for detecting breast cancer.