title: Intraoperative localization of colorectal cancers using radiolabelled monoclonal antibodies.
abstract: Radiation detectors may allow the intraoperative localization of small cancer deposits following administration of radiolabelled tumour-associated antibodies. This technique was evaluated in 16 patients with colorectal tumours (14 cancers, one adenoma, one lipoma) with the 111In-labelled monoclonal antibody (MAb) ICR2 which recognizes the tumour-associated epithelial membrane antigen (EMA). At operation counting was carried out (3 x 20 s per site) using a hand-held radiation probe over the primary lesions and any palpable lymph nodes in the mesocolon. The tumour to normal colon (T/NC) ratio of counts recorded at operation was more than 1.5:1 in eight of the 14 patients with cancer (mean(s.d.), 1.54(0.41):1) and 0.91:1 and 1.06:1 respectively in the two patients with benign tumours. Node to normal colon ratios were higher in lymph nodes containing metastases. The uptake of radiolabelled antibody (T/NC ratio) was higher in EMA-expressing cancers than in those not expressing the target antigen (mean(s.d.), 2.45(0.65):1 versus 1.40(0.20):1, P = 0.019). An abdominal tumour model was also developed. Radioactively filled containers of 0.5-10 ml representing tumour deposits were suspended in a tank of 111In solution representing the background activity found in normal tissues. The ratio of radioactivity in the 'tumour' to that of background varied from 2:1 to 8:1. The 'tumour' was considered to be detectable if the mean counts recorded over the 'tumour' exceeded the mean of counts recorded over background by three standard deviations. At a ratio of 2:1 only 'tumours' greater than 5 ml could be detected with a sodium iodide probe and those over 10 ml could be detected with a cadmium telluride (CdTe) probe. At a ratio of 8:1, 'tumours' of 0.5 ml could be detected with either probe. At all ratios and counting periods the NaI probe was more sensitive than the CdTe.
authors.affiliation: Department of Surgery, University College, Middlesex School of Medicine, London, UK.
authors.forename: B R
authors.initials: BR
authors.lastname: Davidson
authors.forename: W A
authors.initials: WA
authors.lastname: Waddington
authors.forename: M D
authors.initials: MD
authors.lastname: Short
authors.forename: P B
authors.initials: PB
authors.lastname: Boulos
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000032:analysis; D003106:Colon / Q000601:surgery; D003110:Colonic Neoplasms / Q000175:diagnosis* / Q000276:immunology / Q000601:surgery; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes; D007432:Intraoperative Period; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000276:immunology / Q000601:surgery; D012007:Rectum / Q000601:surgery
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D007205:Indium Radioisotopes