Analysis of patient survival in a Phase I trial of systemic targeted α-therapy for metastatic melanoma

Targeted alpha-therapy is an experimental approach to the management of cancer. Short range alpha-particle radiation from a radioisotope attached to a targeting monoclonal antibody kills targeted cancer cells. Survival results are analyzed from a previously reported Phase I study of systemic targeted alpha-therapy for patients with stage IV metastatic melanoma or in-transit metastases. Following intravenous administration of 46-925 MBq of the alpha-immunoconjugate, (213)Bi-cDTPA-9.2.27, 38 patients were followed to observe response and toxicity. Responses were measured by physical examination, computed tomography at 8 weeks and blood sampling. Toxicity was monitored by blood pathology, urine analysis, glomerular filtration rate and human antimouse antibody response. The maximum tolerance dose was not achieved as there were no adverse events of any type or level. However, an objective partial response rate of 10% was observed, with 40% stable disease at 8 weeks and a median survival of 8.9 months. These results were unexpected because of the short half-life of the (213)Bi and short range of the alpha-radiation. Survival analysis demonstrated melanoma-inhibitory activity, disease stage, lactate dehydrogenase and treatment effects to be significant prognostic indicators for survival.