Fast Cancer Uptake of ^99mTc-labelled Bombesin (^99mTc BN1)

Abstract

In human blood, breakdown of gastrin-releasing peptide and other bombesin-related peptides occurs in less than 15 min. This quick enzymatic cleavage might impair the diagnostic use of labelled bombesin (BN). ^99mTc-labelled bombesin (^99mTc BN1) was injected intravenously and dynamic uptake data were acquired for diagnosing 26 cancers of different origin: 15 breast, 3 prostate, 5 colo-rectal, 1 pancreas, 2 small cell lung cancers and 1 gastrinoma. Background subtracted tumour uptake data were plotted against time and fitted with known mathematical functions. Twenty-three out of 26 cancers showed rapid increase of radioactivity followed by a radioactivity plateau, with some oscillations around the average plateau value. The time to 80% of max activity (T₈₀) was the reference parameter to measure and to compare the uptake speeds. The slowest T₈₀ was 7 min in one T1b breast cancer, gastrinoma reached T₈₀ in 5 min and node-positive prostate cancers in 2 min. N+ breast cancers showed T₈₀ at 3.62±0.75 min, N- breast cancers at 5.5±0.88 min (p<0.02). When all the tumours were considered, N+ tumours showed T₈₀ at 2.68±1.03 min and N- cancers at 5.5±0.82 min. In all the cancer types, the uptake of ^99mTc BN was faster than 10 min. This result shows the ability of ^99mTc BN to image tumours. The faster uptake by N+ versus N- cancers probably depends on the higher blood flow in N+ cancers.