Useful radioactivity
Russia has developed "radioactive bullets" against cancer
Tatiana Pichugina, RIA Novosti
Today, incredible successes have been achieved in the treatment of cancer, which could not have been dreamed of at the end of the XX century. At the forefront is nuclear medicine, which has been successfully developed for 60 years in Obninsk at the A. F. Tsyba Medical Radiological Research Center. On the Day of the Fight against Cancer, RIA Novosti tells about the unique drugs and technologies created there that save the lives of thousands of patients.
Treatment with charged ions
Three years ago in A proton therapy center has opened in Obninsk, where the most severe tumors are treated. Irradiated with a beam of protons from the accelerator. Only not scientific, but compact medical.
A ring synchrotron with a diameter of only five meters was installed in a separate building. Patients are brought here, seated in a special chair, put on a mask and conduct a session.
Protons penetrate into tissues to a depth of seven to ten centimeters, while the beam is practically not scattered. All his energy is splashed out at the end point of the run — the peak of the Bregg. The particles infect cells and DNA. The most difficult thing is to choose the right parameters to direct the beam precisely into the tumor without affecting the surrounding tissues. It's easier with protons than with electrons and photons.
Scientists compare a proton beam with a scalpel, which literally burns out a malignant formation. Only unlike a real tool, it does not injure neighboring tissues. This means that it can be used for inoperable tumors in the head and neck, next to critical organs.
"The machine is so elegantly made that it can be operated by literally several people — operators, medical physicists. All have high qualifications that allow for high—quality treatment," notes Vyacheslav Saburov, engineer of the Department of Radiation Biophysics at the A. F. Tsyba MRSC.
This unique installation was invented by a Russian scientist, an employee of the Physics and Technology Center of FIAN Vladimir Balakin. He started in Novosibirsk under the guidance of the Soviet nuclear physicist Hersh Budker, then moved to the science city near Moscow Protvino. There, in the 1990s, he realized his ideas. In 2017, his proton therapy complex "Prometheus" received the status of a medical device. And the inclusion in the list of available VMP (high-tech medical care) has helped to expand the circle of patients. Several installations were purchased by foreign scientific and medical organizations.
"There are three such accelerators operating in the USA, and the first proton center based on that ring was created in Australia," Saburov clarifies.
According to him, Prometheus is much cheaper than its foreign counterparts. And this is the main thing for mass healthcare.
"It was very important to build it in Obninsk in order to develop this technology and make it available to patients from all over the country," the physicist adds.
There are now three proton therapy centers in Russia, including in Dimitrovgrad and St. Petersburg. And you need at least a hundred. In Obninsk alone, six hundred patients received treatment in a year.
Another breakthrough method is being developed here — carbon ions. These are quite heavy particles that require more energy to disperse. IFVE scientists in Protvino have made a separate output channel from large scientific accelerators. Tests on cell and animal cultures have been going on for years. The results are very encouraging. Physicists are ready to design a full-fledged medical center for carbon therapy.
Bragg peaks for different types of radiation. On the right you can see that protons and carbon ions brake sharply at the end of their run, dumping all the energy.
Useful radiation
"More than 80 years ago, on March 31, 1941, radioactive iodine was used for the first time in the world to treat a patient with thyrotoxicosis. This is considered the day of the emergence of theranostics: therapy plus diagnosis. Iodine has become the most popular drug in radionuclide therapy, we have been using it since 1982," says Valery Krylov, head of the Department of radiosurgical treatment with open nuclides of the MRSC.
A radioactive isotope is an unstable atom that emits energy and eventually turns into another chemical element. So, iodine-131 emits soft gamma and X-ray radiation, harmful to cells. This isotope, like ordinary iodine, is purposefully absorbed by thyroid cells to generate hormones, which made therapy possible.
Radionuclides accumulate in tissues, they are clearly visible when scanned in a gamma camera and PET tomograph. Diagnosis is often combined with treatment using the same drug.
In addition to iodine, many isotopes are used, for example, samarium-153. By the way, it is also received in Obninsk. However, before treating with these radionuclides, you need to get them in the form of a drug, that is, combine them with a carrier that delivers the drug to cancer cells. This is the essence of targeted therapy.
It was at the MRNC that a targeted drug based on rhenium-188 was created and tested for the first time in the world. Now they are experimenting with lutetium-177 for the treatment of prostate cancer.
The way for this method was paved by the discovery of special molecules on the surface of prostate cells — prostate-specific membrane antigens (PSMA). When cells degenerate into cancer cells, the concentration of PSMA receptors increases. It remains only to create a binding molecule (ligand) that recognizes PSMA receptors and attaches to them, and hang a radioactive isotope on it. Such a complex is launched into a vein, the ligand finds a tumor in the bloodstream, and the radionuclide begins to destroy it.
"It was invented to detect metastases. Now a live charge is attached to the carrier, it kills cancer cells with the help of alpha and beta radiation," explains Vasily Petriev, head of the laboratory of experimental nuclear medicine.
All elements of the targeted drug are obtained in Russia. The peptide carrier is supplied by Pharmsintez, and lutetium-177 is produced in Dimitrovgrad.
To make a targeted drug, you need a lot of experiments, including on animals. They are injected with malignant cells of the human prostate gland, injected into the caudal vein with medicine and see what happens.
Lutetium-177 is intended for the most advanced tumors that have given multiple metastases. 30 patients have already received experimental treatment at the clinic since May 14, 2021, and clinical trials are ahead.
"Two or three decades ago, the survival rate was several times lower, because there were no such capacious treatment regimens for breast and prostate cancer. Now the situation has improved tremendously, including due to targeted therapy, an abundance of radiopharmaceuticals," Dr. Krylov emphasizes.
Nuclear Briefcase
In order for radionuclides to be in any cancer clinic in the country and the world, they need to be transported safely. For this purpose, there are special sealed containers in which solutions are also prepared — generators created at the A. I. Leipunsky Institute of Physics and Energy. "If it falls even from an airplane, it will remain intact," Nikolai Nerozin, the scientific director of the NTC of Isotopes and Radiopharmaceuticals of the FEI, seriously notes.
Inside there is a glass column with a substance that sorbs the mother radionuclide. In this case, it is tungsten-188 with a half-life of 69 days. Its daughter isotope rhenium-188 is used in radiopharmaceuticals.
"The rhenium generator lasts up to six months, is designed for about one hundred servings. The radiopharmaceutical is obtained from it in the clinic and immediately applied," the physicist comments.
Inside there is a glass column with a substance that sorbs the mother radionuclide. In this case, it is tungsten-188 with a half-life of 69 days. Its daughter isotope rhenium-188 is used in radiopharmaceuticals.
"The rhenium generator lasts up to six months, is designed for about one hundred servings. The radiopharmaceutical is obtained from it in the clinic and immediately applied," the physicist comments.
This year, scientists from the FEI registered their invention and can now send rhenium-188 to different regions to experiment with it. In Obninsk, they are trying to create microspheres with this isotope, as well as in combination with albumin. There is not a single drug with rhenium-188 in the world that has passed all stages of clinical trials, and Russia has a chance to become a leader in this direction.
The FEI also produces actinium-255 isotopes, which are called the future of nuclear therapy. They are obtained only in Germany and the USA, mainly by irradiation of radium-266 on an accelerator using a photonuclear reaction.
This isotope lives for several days, so it constantly needs to be worked out. In a year in the world it is possible to collect only 1.5 curies, and a hundred is required. In order to extract more, it is necessary to develop new approaches, for example, in the Research Institute in Dimitrovgrad, this is done in a reactor. "A unique isotope with a half—life of ten days, it has a very small mileage, but a lot of radiation energy, and if you deliver it directly to the tumor cells, it will kill only them," concludes Nikolai Nerozin.
In the near future, scientists intend to find a transport molecule for actinium-255.
This year, scientists from the FEI registered their invention and can now send rhenium-188 to different regions to experiment with it. In Obninsk, they are trying to create microspheres with this isotope, as well as in combination with albumin. There is not a single drug with rhenium-188 in the world that has passed all stages of clinical trials, and Russia has a chance to become a leader in this direction.
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