BIOKINETICS OF INDIUM-111-BLEOMYCIN COMPLEX IN HEAD AND NECK-CANCER -IMPLEMENTATIONS FOR RADIOCHEMOTHERAPY

Bleomycin (BLM) has been used successfully for treatment of head and n eck cancer. Combining radionuclide therapy with chemotherapy is a fasc inating possibility. We have studied the biokinetics of BLM labeled wi th indium-111 (In-111). A complex formed at low pH had an activity of 100 MBq/mg BLM. This substance was intravenously injected into 10 head and neck cancer patients in escalating doses of 75, 175, and 375 MBq. Scintigraphic data from these patients were compared with tissue samp les obtained at surgery. The activity distribution and penetration int o tumor tissue was not affected by increasing the injected activity. I n-111-BLMC uptake was directly proportional to Ki-67/MIB-1 activity an d number of mitoses in tumor tissue. Based on the biokinetics, dosimet ric calculations for In-111 and In-114m have been performed. S values for realistic geometry (a phantom designed from Patient CT) have been calculated. In-114m could deliver a 4-fold absorbed radiation dose int o the tumor compared with In-111. We think that In-111-BLMC could be u sed for radiochemotherapy in head and neck cancer or adjuvant Auger-el ectron therapy using In-114m combined with BLM. Further studies on cel lular dosimetry should be undertaken.