In radionuclide or radioisotope therapy (also known as radiopharmaceutical therapy and molecular radiotherapy), a radioactive substance administered to the patient intravenously or orally is taken up by the targeted organ or tissue via normal metabolism and radiates locally there for a relatively short period. The radiation effect is utilised both for diagnostic and radiotherapy purposes.
The impact of radionuclide therapy is based on the local radiation impact of a radioactive substance taken up by cancer cells, destroying the tumor cells. The formation of a combination that is taken up by the tumor and destroys cancer cells is always an individually tailored process which requires expertise from a broad range of specialities.
Radionuclide therapies are an increasingly used form of treatment in various cancers. This is due to the fact that an increasing number of cancer tracers have been identified that allow the use of targeted radionuclide therapy. Lymphomas, for instance, can be treated with radiolabelled antibodies that are taken up by cancer tissue and destroy it by means of radiation and antibody formation.
PET-CT and SPECT-CT imaging is an integral part of radionuclide therapy. It gives an idea of the extent to which the radioactive material accumulates in the tissues and helps provide an estimate of the required therapeutic dose and its effects. In treatment, a sufficient dose of radiation is delivered to the tumor tissue, which is confirmed by imaging. It may sometimes take several treatment sessions to achieve a sufficient radiation dose
Rare neuroendocrine tumors can be treated by short-range radiation from a peptide that is readily taken up by cancer tissue. The most common form of radionuclide therapy is the use of radioactive iodine in thyroid cancer, where even the cancer metastases collect iodine and shrink in size as their cells are locally destroyed by short-range radiation. Pain caused by bone metastases can be treated using short-range radiopharmaceuticals that are taken up by bone. Radionuclide therapy is currently included in the Nordic treatment guidelines for neuroendocrine tumors. Very recently, radionuclide therapies have been introduced in the treatment of pancreatic cancer, liver cancer and prostate cancer, for example.
At Docrates, the radionuclide therapy of bone metastases is based on tracers that are taken up by the accelerated metabolism of bone forming cells in the close vicinity of the bone metastases. We have in use the alpha radiator Ra-223 (radium), which treats bone metastases locally based on the increased metabolism of calcium in the bone metastasis, and beta radiator Sm-153 (samarium), whose effect is based on locally increased phosphorus metabolism in the bone metastasis.
Since the early 2000s, various radionuclide therapies have also been used to treat non-Hodgkin’s lymphoma, for example. The treatments are based on radiolabelled antibodies which combine the effect of the antibody itself and the cell-destroying effects of radiation.
The potential of radionuclide therapy to treat certain rarer solid tumors (e.g. feocromocytomas and neuroblastomas) and haematological conditions (e.g. leukemia), as well as in intracavitary and intravascular treatments, has been known for some time, but the number of patients treated has been small. The majority of these treatment methods require collaboration between physicians from a number of specialities, and only a few centres in the world have been able to carry out such treatments.