With rare earths against cancer

With rare earths against cancer

European researchers produce in an accelerator four radionuclides, which promise better diagnosis and effective treatment. Experiments with mice yielded promising results.

With "customized" radioisotopes to tumors can be controlled efficiently in the future. In a preclinical study has managed a European Research Group, the effectiveness of radionuclides of the element terbium (chemical symbol: Tb) – a metal of the rare earth – To demonstrate for cancer therapy. Unlike radioactive isotopes have long been used, incurred mostly as "byproducts" of commercial nuclear reactors, Terbium has obviously ideal properties for medicine.

The Radionuklidmedizin cancer patients treated with radioactive substances, are injected into the bloodstream. The radiation from these substances can destroy cancer cells and stop the growth of tumors in the body of the patient or even regress tumors. Since the emitted radiation does not distinguish between healthy and diseased tissue, it is necessary, the radioactive isotope "packaged" in a biological component, which binds specifically to the tumor cells. In this way, the active ingredient concentrate on diseased tissue and record there in the fight against cancer.

Tailoring in the early phase

Many of the commonly used in nuclear medicine isotopes such as iodine-131 or yttrium-90 have often medically no ideal characteristics in terms of energy as well as the type and duration of radiation. "It would be ideal, select the most suitable radioisotopes in an early phase of drug development to ", explains the physicist from Ulli Köster Institut Laue-Langevin (ILL) in Grenoble. It is their colleagues at the Paul Scherrer Institute Swiss in Villingen, the Technical University of Munich and the European research center CERN in Geneva succeeded, produce four customized terbium isotopes, that could meet the medical requirements may. The results of the first animal tests were promising.

Nuclides for diagnosis and therapy

To prepare the artificial radionuclides with mass numbers 149, 152, 155 and 161 The scientists bombarded films of tantalum and gadolinium neutron or high-energy protons. The Terbiumisotope differ in the number of neutrons and in their mode of radioactive decay, of chemical and biological point of view, but they are quite similar to each other. That's a big advantage for the Radionuklidmedizin. Packaged in a substantially consisting of the vitamin B9 molecular complex, Radioisotopes can bind to specific tumors, where they exert their effect.

This is pronounced differently depending on the isotope: Sun emitting isotopes terbium-155 and 161 Gamma radiation, the body of the patient almost completely leaves again, so that these two radionuclides particularly for the diagnosis and localization of tumors are. Terbium-152 emits positrons contrast, the rapidly decay into gamma rays. This isotope is therefore ideally suited for the diagnosis with positron emission tomography. Therapeutic benefits are particularly terbium-149 and 161. The latter emits beta rays, which penetrate a few millimeters to a few centimeters deep into the tissue and destroy cells. The securities issued by terbium-149 alpha particles penetrate only a few tenths of a millimeter into the tissue. Terbium-161 emits beta particles in addition to the more so-called Auger electron from the atomic shell, which, because of their lower energy only a few micrometers wide, which is ideal for fighting small tumors and metastases.

Promising pilot study

The researchers led by Koster have analyzed the potential diagnostic and therapeutic benefits of Terbiumquadrupletts in mice. In five out of eight animals was a regression of the tumors observed. However vacate Koster and his colleagues themselves, that the number of animals was too small, to draw any conclusions from these results too much can. That new procedures in oncological clinical trials provide promising results, in clinical trials but disappoint, is an all too familiar pattern in cancer medicine. Published in the journal "The Journal of Nuclear Medicine" (two:10.2967/jnumed.112.107540) published series of experiments has the character of a pilot study. It shows, that the concept works as such – albeit in such tumors, have suitable receptors for the vitamin complex, in which one embeds the Terbiumnuklide.

Chance für bessere Therapie

For Radionuklidmedizin could study despite this constraint be an important advance. Already, always a shortage of certain nuclides. Institutions such as CERN or the ILL, which occur mainly with the study of fundamental physical relationships in appearance, could jump in here, Koster says: "You can speed up the development of promising new therapies, by providing radioisotopes in high quality, which are not available commercially until now. "

Those: F.A.Z.

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