【Health Frontiers】
Guangming Daily reporter Zhang Xiaohua
When it comes to medical isotopes, you may feel unfamiliar. But you may have had a breath test during your check-up — take a capsule of carbon-14 urea, take a breath and exhale it slowly. It doesn't take long for you to know if you are infected with H. pylori. This test, known as the carbon-14 breath test, is currently one of the most convenient ways to check for H. pylori infection. A key role in this is the radioactive medical isotope carbon-14.
Not only carbon-14, in recent years, with the close integration of nuclear technology and the medical field, more and more medical isotopes have been used in clinical practice. Although they may seem like "don't get close to the living", in fact, they are the basis of nuclear medicine diagnosis and treatment, and are widely used in the diagnosis and treatment of a variety of diseases.
Molybdenum-100 isotopes and ytterbium-176 isotopes manufactured by the Institute of Physical and Chemical Engineering of the Nuclear Industry. Photo by Xuan Shuyi/Guangming Pictures
He has made great achievements in the diagnosis and treatment of diseases
If you want to figure out what medical isotopes are, you have to start with "isotopes".
Different atoms of the same element with the same number of protons and different numbers of neutrons are "isotopes", which will spontaneously emit rays, which are called "radioisotopes", and the radioisotopes used in medicine are medical isotopes.
For example, iodine-131, a well-known medical isotope, is an important magic weapon for the treatment of thyroid diseases. "Thyroid tissue is like a 'snake' ingesting iodine, if the ordinary iodine is replaced with radioactive iodine-131, which is orally entered into the body by the patient, it is selectively 'trapped' by thyroid cancer cells, and iodine-131 releases β rays during the decay process, which can kill small lesions without affecting the surrounding normal tissues. Li Linfa, an expert from the Department of Nuclear Medicine of Zhejiang Provincial Cancer Hospital, said.
If you are new to medical isotope therapy, you must have heard of another job in the Department of Nuclear Medicine - nuclear medicine examination, the most famous of which is positron emission tomography (PET-CT). It uses a radionuclide for imaging, and then uses CT anatomical structure for joint diagnosis, which has the characteristics of sensitivity, accuracy, specificity and precise positioning, which can achieve the purpose of early detection of lesions and diagnosis of diseases.
Different medical isotopes are used for different diseases. With the development of modern medicine, more and more medical isotopes have entered clinical applications. Iodine-131, carbon-14, iodine-125, lutetium-177, yttrium-90 and other 10 kinds of medical isotopes form a huge "group army" and become an important force in the diagnosis and treatment of major diseases.
Li Linfa said: "Now, in addition to playing a role in the fields of thyroid cancer and neuroendocrine tumors, medical isotope therapy is also showing great power in solid tumors such as liver and pancreas, as well as tumor bone metastasis. ”
Despite the fact that medical isotopes are so "hardcore", most people are still wary of it: will it cause cancer, will it cause infertility, will it cause a decrease in the body's immunity......
In fact, it is not necessary to talk about the discoloration of "nuclear".
With the continuous improvement of equipment and technology, the sensitivity of treatment and examination has been greatly improved, and the dosage and half-life of medical isotopes have been greatly reduced. "In our hospital, more than 1,200 cases of iodine-131 treatment after thyroid cancer surgery are seen in a year. Many female patients can get pregnant normally within six months to a year after treatment. According to Li Linfa, the mainland has strict regulations on the application of nuclear technology to ensure proper application and safety.
Demand continues to grow
At present, cardiovascular diseases, malignant tumors, and neurodegenerative diseases are seriously affecting human health. The use of the unique advantages of medical isotopes in diagnosis and treatment has become an indispensable means to improve people's health.
According to the results of nuclear medicine census in recent years, the average number of people undergoing nuclear medicine examinations per 10,000 people in the world is about 64, including 695 in the United States, 240 in the European Union, 111 in Japan, and 19 in the mainland, which is only about 30% of the global average and far lower than the level of developed countries in the world.
Compared with the level of nuclear medicine treatment in developed countries in the world, the actual demand for medical isotopes in mainland China will continue to grow. Among them, the 8 medical isotopes commonly used in the field of nuclear medicine are conservatively estimated to increase at a rate of 5%~30% per year, and the total demand is expected to increase by more than 10 times by 2030.
Taking iodine-131 as an example, based on the estimated incidence of thyroid disease in recent years, the demand for iodine-131 in the international market is expected to reach 110,000 curies in 2030. As the country with the largest use of iodine-131 at present, the demand for iodine-131 in the mainland market will be 20,000 curies per year in 2023, and the market demand is expected to reach 42,000 curies per year by 2030.
The reality is that although the mainland has a large demand for medical isotopes and a high annual demand growth rate, most of them rely on imports. For example, molybdenum-99 required for routine nuclear medicine diagnosis is all imported, and 80% of the therapeutic nuclide iodine-131, other important therapeutic nuclides iodine-125, yttrium-90, lutetium-177, radium-223, etc. are all imported. The lack of independent and stable supply of medical isotopes has become the key to restricting the development of radiopharmaceuticals and nuclear medicine in mainland China.
Not only that, the current international market for medical isotopes is also facing supply problems. In recent years, the global supply of medical isotopes has relied on medical research reactors in Canada, France, Australia and other countries, but most of these research reactors have been out of service and are expected to be shut down around 2025 due to high maintenance costs, difficult waste solutions, and safety risks. Among them, the OSIRIS reactor in France and the National General Research Reactor in Canada have permanently ceased production in 2015 and 2018, respectively, resulting in a reduction of about 30% in global molybdenum-99 production at the end of 2016, and indirectly leading to an increase in the price of clinical molybdenum-technetium generator applications.
In view of this, in June 2021, the "Medium and Long-term Development Plan for Medical Isotopes (2021-2035)" jointly issued by eight departments including the China Atomic Energy Agency (CAEA) clearly aims at the needs of medical isotope production and radiopharmaceutical development. This sounded the clarion call to establish a stable and independent medical isotope supply guarantee system and promote the research and development of medical isotope technology and industrial development.
Break the constraints of isotope drugs
Not long ago, the China Nuclear Power Research and Design Institute (hereinafter referred to as the Nuclear Power Institute) medical isotope test reactor of China National Nuclear Corporation officially started construction in Sichuan.
"After the completion of the medical isotope stack, it will achieve an annual output of 100,000 curies of molybdenum-99 and 20,000 curies of iodine-131, exceeding the current domestic demand. Li Qing, the chief designer of the project, said that the medical isotope stack can solve the situation that two medical isotopes have long been dependent on imports and are controlled by others, and meet the nuclear medicine diagnosis and treatment needs of domestic patients. At the same time, this medical isotope reactor uses uranyl nitrate aqueous solution as fuel and target material, which has inherent advantages far beyond conventional reactors in the field of nuclear safety and environmental protection.
"The cost of producing medical isotopes alone is sky-high. Li Qing told reporters that at present, medical isotopes in mainland China generally adopt the "free-riding" mode for production, that is, when the reactor performs other tasks, it is produced by the way.
"Medical isotope reactors are dedicated production reactors, and reactor operating hours can be scheduled according to the needs of pharmaceutical production. For example, Li Qing said that molybdenum-99 and iodine-131 are both products with short half-lives, especially molybdenum-99, which has a half-life of only more than 60 hours.
In recent years, the Nuclear Power Institute has launched the innovative research and development of more than 10 commonly used medical isotopes, including carbon-14, phosphorus-32, strontium-89, iodine-125, iodine-131, lutetium-177, new molybdenum-technetium (99Mo-99mTc) generator, actinide (227Ac-223Ra) generator, strontium yttrium (90Sr-90Y) generator, tungsten-rhenium (188W-188Re) generator, etc. Among them, the first five individual isotopes have overcome technical difficulties, have the conditions for engineering transformation, and can be produced at any time to gradually meet domestic demand.
"Our goal is to break the situation that isotope drugs are controlled by others, form a complete industrial chain, and catch up with foreign countries in terms of industrial scale and technical level. Yao Gang, president of the Nuclear Power Institute, said that in 2021, the National Engineering Research Center for Medical Isotopes and Drugs was officially approved, relying on the center, the Nuclear Power Institute introduced 8 medical isotope production lines and plans to put into operation in 2024, with a design capacity of 30,000 Curie iodine-125, 10,000 Curie lutetium-177, 200 Curie carbon-14, 50 Curie radium-223 and other 8 kinds of medical isotopes urgently needed in the domestic market, which will play an important role in establishing an independent guarantee system for medical isotopes.
Guangming Daily (2024-04-20 07 edition)
Source: Guangming Net-Guangming Daily