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 neck cancer. Combining radionuclide therapy with chemotherapy is a fascinating possibility. We have studied the biokinetics of BLM labeled with 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 samples obtained at surgery. The activity distribution and penetration into tumor tissue was not affected by increasing the injected activity. In-111-BLMC uptake was directly proportional to Ki-67/MIB-1 activity and number of mitoses in tumor tissue. Based on the biokinetics, dosimetric 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 into the tumor compared with In-111. We think that In-111-BLMC could be used for radiochemotherapy in head and neck cancer or adjuvant Auger-electron therapy using In-114m combined with BLM. Further studies on cellular dosimetry should be undertaken.