A low pH 111In-bleomycin complex: a tracer for radiochemotherapy of head and neck cancer

Bleomycin (BLM) is a well known natural antibiotic. It is toxic to dividing cells and has been used for the treatment of several forms of cancer. BLM has been labeled with various cations, but most of them have turned out be unstable in in-vivo experiments. In-BLM demonstrated high bone marrow uptake, but using 111In-bleomycin complex (BLMC) formed at low pH, the low in vivo stability and high bone marrow seeking behavior of the molecule could be avoided. The idea of using BLMC in combined radiotherapy and chemotherapy is intriguing. In this study we examined the effects of 111In-A'2a-c-BLMC in the treatment of 31 head and neck cancer patients. Findings were compared with those of surgery, and pre-operative radiology. The injected activity was 85-110 MBq, and the specific activity was approximately 100 MBq/mg. The half-life of 111In activity in serum varied from 1.5 to 3.1 hours. Maximum activity in the urine was achieved in all patients within 3 hours, and the average half-life in urine was 2 hours. In most patients 50% was excreted within 3 hours, in some 70%; in all patients > 95% of the activity was excreted within 22 hours. In surgical samples from 24 patients the best tumor-to-tissue ratios were: fat 60:1, bone 17:1, muscle 12:1, blood 3.6:1. All patients were examined on the injection day with ultrasonography of the neck. Using 111In-BLMC we missed a few small lymph nodes in 2 patients, but there were no false positive findings.(ABSTRACT TRUNCATED AT 250 WORDS)