A tumour spheroid model for antibody-targeted therapy of micrometastases.

Human neuroblastoma cells grown as tumour spheroids were briefly incubated with a conjugate of 131I and an anti-human neuroectodermal monoclonal antibody UJ13A. Unbound 131I was removed by washing and the spheroids observed in culture conditions for up to 4 weeks. Spheroid response to irradiation was evaluated as time to reach 10x treatment volume and proportion of spheroids sterilised. Spheroid growth was found to be affected by both the activity of 131I-UJ13A and the duration of the incubation. Na[131I], 131I-HSA, 131I labelled non-specific antibody and unlabelled antibody were found to be relatively ineffective compared to 131I-UJ13A. The tumour spheroid model has applications in the evaluation of antibodies or antibody fragments and different radionuclides which may be considered for radioimmunotherapy of micrometastases.