Radioimmunotherapy: Treatment, Effects & Risks

Radioimmunotherapy is a relatively new treatment method for cancer patients. Its advantage over conventional treatment methods such as chemotherapy or traditional radiation therapy is the high selectivity of the procedure. The goal of the therapy is to produce a high dose of radioactive radiation in the vicinity of the tumor cells, which kills the tumor cells.

What is radioimmunotherapy?

Radioimmunotherapy is a relatively new method of treating cancer patients. The goal is to produce a high dose of radioactive radiation in the area surrounding the tumor cells, which kills the tumor cells. So-called conjugated radiopharmaceuticals are used. These are a combination of a carrier molecule and a radioisotope. The carrier molecules are usually antigens or peptides. These specifically dock onto surface structures of the tumor cells, whereupon the radioisotope, usually a short-range beta emitter, destroys the tumor cell. The antibody must be structured in such a way that it binds exclusively to tumor cells and spares healthy tissue. The two components are coupled via an intermediate molecule.

Function, effect, and targets

In the case of chemotherapy, all rapidly dividing cells in the body are attacked. In addition to tumor cells, these include the mucosal cells of the mouth, stomach, and intestines, as well as cells of the hair roots. This almost always leads to severe side effects such as diarrhea, hair loss, mucosal disorders and blood count changes. Irradiation of the tumor from the outside by means of X-rays, electron or proton radiation usually also damages parts of the surrounding healthy tissue. In addition, certain organs can only tolerate a certain dose, which must not be exceeded. In radiation therapy, several weak beams are now often used, which cross and add up in the tumor to be treated. However, the burden on healthy tissue remains significant in many cases. In the case of radioimmunotherapy, antibodies injected into the bloodstream specifically seek out tumor cells throughout the body. Thus, the conjugated radiopharmaceuticals can also detect cancer sites in the patient’s body previously undetected by imaging and clinical examinations, as the entire body is scanned via the bloodstream. The tumor cells are irradiated inside the body at close range and are consequently exposed to a particularly high dose of radiation, while healthy tissue is spared. Since the radioisotopes attach directly to the tumor cells, a lower radiation intensity is needed overall because of the shorter distance to the radiation source. In addition, tumor cells in neighboring lymph nodes, which cannot be reached via antigens, are also reached by the radiation. This is referred to as the “crossfire effect”. The radioactive substance used dissipates with a half-life of typically hours or days, and much of it is excreted through the kidneys in the urine. In some cases, additional drugs and fluids are given to protect the kidneys. In order for radioimmunotherapy to be possible, a surface structure of the tumor cell must first be identified that is found exclusively there. An antigen must then be produced that binds only to this type of surface structure. Finding such specific surface structures on the respective tumor cells and producing suitable antigens are the main difficulties in developing this therapy. This has been achieved for some tumor types, such as non-Hodgkin’s lymphoma, for example. The surface structure in this case is the CD-20 structure and the beta emitter used is yttrium. Treatment in this case can even be done on an outpatient basis. There are promising approaches to combine radioimmunotherapy with chemotherapy. So far, only very few types of cancer are known in which radioimmunotherapy has been successfully applied. The first and for a long time the only one was non-Hodgkin’s lymphoma. Radioimmunotherapy is a fairly new therapy that has been used regularly for cancer treatment only since the beginning of the 21st century. In many preclinical studies, and more recently some clinical studies, it has been shown to be more effective compared to chemotherapy. It is a promising concept for the future of tumor treatment and the subject of intensive research worldwide.The main focus here is to explore new possibilities in the production of the carrier molecules.

Risks and side effects

The most common side effect is nausea. Overall, the expected side effects are usually less severe compared with chemotherapy and radiation.