in vivo 19: 1071-1076 (2005) Fast Cancer Uptake of 99mTc-labelled Bombesin (99mTc BN1) F. SCOPINARO1, G. P. DI SANTO1, A. TOFANI1, R. MASSARI2, C. TROTTA2, M. RAGONE3, S. ARCHIMANDRITIS4 and A.D. VARVARIGOU5 1Department of Scienze Radiologiche and 4Faculty of Engineering, University “La Sapienza”, Rome; 2University Hospital “San Andrea”, Rome; 3Li-Tech and ISIB-CNR, Udine and Rome, Italy; 5National Research Center,"Demokritos", Athens, Greece Abstract. In human blood, breakdown of gastrin-releasing show istant action because BN receptors (BNRs) and BNR peptide and other bombesin-related peptides occurs in less than subtypes (BNS) are the same in different tissues; however, 15 min. This quick enzymatic cleavage might impair the the action of the above peptides is prevented by their rapid diagnostic use of labelled bombesin (BN). 99mTc-labelled breakdown in the serum. bombesin (99mTc BN1) was injected intravenously and BN and BN-related peptides are neuro-hormones and dynamic uptake data were acquired for diagnosing 26 cancers neurotransmitters; the three well known human BNS show a of different origin: 15 breast, 3 prostate, 5 colo-rectal, 1 number of functions in the central nervous system (4, 5). pancreas, 2 small cell lung cancers and 1 gastrinoma. BNS is also expressed in several foetal and adult tissues, Background subtracted tumour uptake data were plotted where BN-related peptides act as releasing factors, against time and fitted with known mathematical functions. morphogens and growth factors (6-8). Finally, BN-related Twenty-three out of 26 cancers showed rapid increase of peptides, whose paracrine and autocrine production has radioactivity followed by a radioactivity plateau, with some already been mentioned, act as mitogens, growth and anti- oscillations around the average plateau value. The time to 80% apoptotic factors on several epithelial cancers, such as of max activity (T80) was the reference parameter to measure breast, prostate and small cell lung carcinomas (9-12). and to compare the uptake speeds. The slowest T80 was 7 min The rationale of labelling BN-like peptides with gamma- in one T1b breast cancer, gastrinoma reached T80 in 5 min ray-emitting radioisotopes (13, 14) is based on the intense and node-positive prostate cancers in 2 min. N+ breast overexpression of BNRs in a large variety of epithelial cancers showed T80 at 3.62±0.75 min, N– breast cancers at tumours. This fact makes labelled BN most suitable as a 5.5±0.88 min (p<0.02). When all the tumours were cancer seeking agent. Initial pilot and phase I diagnostic considered, N+ tumours showed T80 at 2.68±1.03 min and trials with the first of a series of BN-like peptides, labelled N– cancers at 5.5±0.82 min. In all the cancer types, the uptake with technetium (99mTc-BN-1), have confirmed this of 99mTc BN was faster than 10 min. This result shows the hypothesis (15-21). Rapid cleavage of BN in the serum has ability of 99mTc BN to image tumours. The faster uptake by suggested the synthesis of BN-like labelled peptides with a N+ versus N– cancers probably depends on the higher blood longer BN half-life than native in human blood (22). It is flow in N+ cancers. necessary to know if the cancer uptake of intravenously (i.v.) injected 99mTc BN-1 is fast enough for tumours to Bombesin (BN) and related peptides, which are gastrin- accumulate this radiopharmaceutical before its enzymatic releasing peptides (GRP), and neuromedin B (NMB) in destruction in human serum. mammalians, mainly act through their paracrine or their The tissue uptake of molecules undergoing internalisation autocrine secretion (1-3). GRP and NMB would be able to is generally faster than the uptake of molecules that only bind to membrane or extracellular structures (23) and the internalisation of small peptides is faster than the internalisation of large globulins, such as antibodies (24). Correspondence to: Francesco Scopinaro, Nuclear Medicine, However, it is well known that a small labelled peptide such University of Rome "La Sapienza", "S. Andrea" Hospital, Via di as 111In octreotide takes some hours before allowing good Grottarossa1038, 00100 Rome, Italy. e-mail: francesco.scopinaro@ quality emission tomography (25-27). uniroma1.it The main aim of the present study was to establish 99m Key Words: Bombesin, breast cancer, prostate cancer, gastrinoma, whether injected Tc BN-1 is taken up by different radiolabelled peptides. tumours before the breakdown of the peptide, whose half- 0258-851X/2005 $2.00+.40 1071 in vivo 19: 1071-1076 (2005) life is about 15 minutes in human blood. A secondary aim Table I. Summary of the results. was to assess whether or not the uptake characteristics can No. pts. Tumour type TN Nodes Best fit Time to 80% clarify the role of regional blood flow and BNR staging of max activity overexpression in cancer. 1 Breast cancer T2N1 + GU 2.5 min Patients and Methods 2 Breast cancer T2N1 + GU 4 min 3 Breastcancer T1cN1 + GU 4 min Patients. Twenty-six patients, 14 with breast cancer, 1 with exocrine 4 Breast cancer T1cN0 – GU 4 min pancreas cancer, 1 with gastrinoma, 2 with small cell lung cancer 5 Breast cancer T1bN1 – Sin GU 6 min (SCLC), 3 with prostate cancer, 2 with colon cancer and 2 with 6 Breast cancer T1bN0 – PO 5 min rectal cancer, were studied with 99mTc BN-1. Out of the 14 patients 7 Breast cancer T1cN0 – Sin GU 7 min with breast cancer, 5 patients showed T1b N0 stage, 5 were T1c N0, 8 Breast cancer T1bN0 – Sin GU 5 min 2 were T1c N1 and 2 were T2 N1. All the prostate cancers were T3 9 Breast cancer T1bN0 – Sin GU 4 min N+, 2 colon cancers were T2 N0, 1 rectal cancer T1N0, 1 T1N1 10 Breast cancer T1bN0 – PO 6 min and 1 T2 N0. 11 Breast cancer T1cN0 – Sin GU 4.5min Thin layer chromatography (TLC), with 75% methanol as the 12 Breast cancer T1cN0 – Sin GU 6 min mobile phase, was used to assess the labelling yield of 99mTc BN-1. 13 Breast cancer T1cN0 – Sin GU 6 min 14 Breast cancer T1cN0 – Sin GU 5.5 min The data were acquired with a double-headed large field of view 15 Colon cancer T2N0 – Sin GU 1.5 min gamma camera fitted with low energy, general purpose collimators. 16 Rectal cancer T1N1 + Sin GU 1.5 min Before starting the SPECT studies, a dynamic set of data was 17 Colon cancer T1N0 – GAV 4 min acquired for each patient. Dynamic studies started at the moment 18 Rectal cancer T2N1 + PO 1.5 min 99m of intravenous injection of Tc BN-1, 185 MBq (5 mCi) in bolus 19 Rectal cancer T1N0 – GAV 4.5 min and lasted 20 minutes with a rate of one frame/minute. 20 Prostate cancer T3N1 + GU 2 min The detectors were differently positioned for different anatomic 21 Prostate cancer T3N1 + GU 2.5 min situations: one detector ventral and the second dorsal to the chest 22 Prostate cancer T3N1 + Sin GU 2.5 min or to abdomen to study the lungs and, respectively, the pancreas 23 SCLC T2N1 + GAV 2 min and left and right lateral for the prostate. Mammary glands were 24 SCLC T1N1 + PO 3.5 min studied in a prone lateral view following the technique of Khalkhali 25 Gastrinoma TxN0 – GU 5 min et al. (28, 29) with two detectors positioned on each breast. Colon, 26 Exocr pancr. cancer T1N0 – PO 6 min pancreas and lung cancers were studied with detectors in anterior and, respectively, posterior view; prostate and rectal cancers were GU, general uptake; PO, polynomial; GAV, gamma variate examined with detectors on the left and right lateral view, with the patient in supine decubitus. Images, ROIs and 99mTc bombesin curves. Regions of interest A dedicated program for automatic selection of best fit of the (ROIs) were selected by the operator on the sum of dynamic experimental data was implemented in the Windows/origin images of each dynamic dataset. Tumour and organ background environment of a personal computer. Normalised background ROIs were always selected (Figure 1); bladder ROI was selected subtracted counts against time were imported from the dedicated- only for patients with prostate or rectal cancer (Figure 2). Actually, to-gamma camera computer to the Windows /origin of a personal radioactive urine was always detectable in the bladder , although computer; counts/time plots were generated for each ROI and the continuous washing of the bladder occurred because of the best fit of experimental curves with MF established by the insertion of a three-way catheter. computer program. Data arising from ROIs were normalised for geometric Data arising from ROIs drawn on dynamic acquisitions of difference by predefined computer programs. The normalised radioactivity are generally presented as time/activity plots and the organ background curve was subtracted from the tumour curve and resulting observed curves are normally fitted with MF. Thus, some displayed on the computer screen. MF, such as straight line, exponential, gamma-variate (GAV), general uptake (GU) and polynomial (PO) functions are familiar Curve fit. The dynamic data of radioactivity arising from ROIs to nuclear medicine operators. Straight line and exponential can be plotted against time (Figure 3) showing time/activity functions are often used to describe physiological behaviours, curves, that we can also call uptake curves because of their independently from nuclear medicine; GAV, GU and PO are more b -ct starting from 0 for activity as well as time representing the i.v. specific. GAV is At=A0 a e , where At is the radioactivity administration, and reaching more or less stable maximum function of time, t is time after administration, A0 is the activity (max).