MEASUREMENT OF HYPOXIA IN HUMAN TUMORS BY NONINVASIVE SPECT IMAGING OF IODOAZOMYCIN ARABINOSIDE

Tumour oxygenation status in individual patients may be assessed using the bioreduction and linkage of 2-nitroimidazole markers to viable hy poxic cells in vivo with subsequent detection by conventional nuclear medicine techniques. Iodoazomycin arabinoside (IAZA) was radiolabelled with Iodine-123 and administered i.v. to 51 patients with newly diagn osed malignancies whose tumours were subsequently imaged by planar and single-photon emission computed tomographic (SPECT) procedures. Quant itative analyses of radiotracer avidity were performed at 24 h post-in jection and tumour-normal tissue ratios of greater than 1.10 were deem ed positive for tumour hypoxia. By this criterion, the frequencies of hypoxia in small-cell lung cancer, squamous cell carcinomas of head an d neck and malignant gliomas were 60% (9/15), 40% (6/15) and 0% (0/11) respectively. The correlation of positive IAZA scans with tumour cont rol and survival in patients with lung cancer and head and neck tumour s is currently under study. Preliminary observations in neck metastase s from squamous cell carcinoma of head and neck tumours indicates decr eased local control at 3 months post-treatment in tumours with IAZA av idity. This study concludes that: (1) I-123-IAZA can be administered s afely and repeatedly as an outpatient routine imaging procedure in can cer patients during initial work-up and follow-up; (2) that retained d rug can be detected by conventional nuclear medicine procedures in ina ccessible deep-seated tumours; and (3) that this technique could prove useful for identifying those patients for whom hypoxia-directed thera py is indicated.