Does immunoscintigraphy serve clinical needs effectively? Is there a future for radioimmunotherapy?

Since 1980, immunoscintigraphy has been performed in thousands of patients, and its clinical value has been demonstrated for selective indications in malignant (early detection of recurrences of colorectal and ovarian carcinomas) and non-malignant (cardiovascular and inflammatory) pathology. However, many clinicians are not yet very convinced of its efficiency. Opinions range between favourable interest and marked scepticism. The causes of this inconclusive verdict include an often moderate target-to-background ratio in images, the immunogenicity of injected murine antibodies and the fact that a true benefit for the patient has not yet been clearly demonstrated in large series of patients. Future prospects could significantly improve this and involve the reduction of non-specific activity in normal tissues (to improve disease target contrast and thus make image interpretation easier) and the decreased immunogenicity of injected immunoconjugates (to permit repetition of examinations). Radioimmunotherapy, an innovative and promising approach, is still limited by numerous problems. The results of clinical studies are still inconclusive, being encouraging only for specific indications. In the future, pre-targetting techniques should allow the rapid elimination of radioactivity from normal tissues, resulting in a significant increase in tumour-to-normal tissue ratios. Progress is also required in the choice of radionuclides and labelling techniques and in methods for dosimetric estimations. The clinical indications of radioimmunotherapy after systemic injection will concern mainly radiosensitive tumours such as lymphomas, small-cell lung cancers and neuroblastomas. After endocavitary injection, radioimmunotherapy could prove efficient in the treatment of micrometastases of ovarian carcinomas. For all indications, this new approach should be combined with other therapeutic modalities.