Radioimmunotherapy – still experimental? Rational, proven indications and future trends

Radionuclide therapy beyond radioiodine

For decades, Iodine-131 has been used for the treatment of patients with thyroid cancer. In recent years, increasingly, other radiopharmaceuticals are in clinical use in the treatment of various malignant diseases. Although in principle these therapies-as in all applications of radionuclides-special radiation protection measures are required, a separate nuclear medicine therapy department is not necessary in many cases due to the lower or lack of gamma radiation. In the following article, four different radionuclide therapies are more closely presented which are emerging in the last years. One of them is the "Peptide Receptor Radionuclide Therapy," the so-called PRRT in which radiolabeled somatostatin (SST)-receptor(R) ligands are used in patients with neuroendocrine tumors. On the basis of radiolabeled antibodies against CD20-positive cells, the so-called radioimmunotherapy is used in the treatment of certain forms of malignant lymphoma. In primary or secondary liver tumors, the (90)Y-labeled particles can be administered. Last but not the least, the palliative approach of bone-seeking radiopharmaceuticals is noted in patients with painful bone metastases.

Diversity in antibody-based approaches to non-Hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) remains one of the most common cancers in the US, with survival dependent on the type and stage of disease. B-cell lymphomas account for approximately 85% of all cases of NHL, and are commonly treated with chemotherapy, or monoclonal antibodies (mAbs) that target CD20 antigens on the surface of malignant tumors. The use of mAbs, either as single agents or in combination with chemotherapy, has made a huge impact on NHL survival rates. Rituximab remains the most commonly used and established mAb, and is used in a wide range of NHLs, but does not produce an effective therapeutic response in all patients. Novel therapeutics with enhanced binding affinity or alternative antigen targets are currently in development and in some cases have demonstrated improved efficacy over currently available treatments. Radioimmunotherapy has been included in transplant conditioning regimens to improve long-term disease control while limiting toxicity. These regimens have been safe, effective, and feasible, and are therefore promising for patients who cannot tolerate high-dose chemotherapy and/or total body irradiation.