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Averting a Medical Radioisotope Shortage

Supply Challenges, Crisis Mitigation Efforts and Alternatives to Medical Radioisotope Mo-99

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IAEA Department of Nuclear Sciences and Applications Director, Meera Venkatesh, and Department of Nuclear Energy Deputy Director General, Alexander Bychkov, highlight the unfolding situation regarding the supply of Mo-99, at the 58th IAEA General Conference side event Medical Radioisotope Mo-99: Supply challenges, Crisis Mitigation Efforts and Alternatives. (Photo: M. Madsen/IAEA)

An impending shortage of a key radioisotope will have an adverse impact on medical nuclear imaging diagnostics unless alternative methods or substitutes are found. This was the key message at a side event called Medical Radioisotope Mo-99: Supply Challenges, Crisis Mitigation Efforts and Alternatives held on 25 September 2014, during the 58th IAEA General Conference.

Molybdenum-99, more commonly referred to as Mo-99, is typically produced in research reactors. It is the parent isotope of technetium-99 (Tc-99m) which is a widely used isotope in nuclear medicine.

Tc-99m, releases gamma rays at about the same wavelength as conventional X-ray diagnostic equipment, and with a short half-life (only 6 hours) is ideal for diagnostic nuclear imaging. A patient can be injected with a small quantity of Tc-99m and within 24 hours almost 94 per cent of it would have decayed and left the body, limiting a patient’s radiation exposure. Today Tc-99m is used in 20-40 million scans annually, which is almost 75 per cent of all procedures in nuclear medicine.

However, many of the reactors producing Mo-99 are ageing, causing longer maintenance periods with some even scheduled for permanent shutdown, leading to an uncertainty of supply.

Three presentations during the side event explained the current state of Mo-99 production and potential crisis mitigation options.

The opening presentation of Joao Alberta Osso Junior, Head of the IAEA Radioisotope Products and Radiation Technology Section, gave a background on the importance of the radioisotope. Expressing the Agency’s concern about the Mo-99 situation, he stressed that alternative options needed to be considered. Helping developing countries to get access to very important radiopharmaceuticals is a priority. He pointed out that some of the IAEA’s activities support the production of Mo-99 without the use of highly enriched uranium (HEU).

A presentation by Thomas J. Ruth, the Canadian representative to the IAEA Standing Advisory Group for Nuclear Application (SAGNA), discussed an ongoing IAEA coordinated research project (CRP) using accelerators to produce Tc-99m. Using Mo-100, supplied from Russia, the project has shown that cyclotrons can produce Tc-99m of a quality suitable for nuclear medicine.

A cyclotron is a complex machine that accelerates charged particles in a vacuum outwards from the centre along a spiral path. During the acceleration process, charged particles gain significant energy. The energized charged particles then interact with stable material that is placed in their path. The interaction transforms stable materials into medically useful radioisotopes that are used to make radiopharmaceuticals.

Ruth explained that Canada has over 25 cyclotrons powerful enough to produce enough of the radioisotope to meet that country’s demands. The biggest challenges faced by cyclotron-produced Tc-99m is that its short half-life limits its deployment range within areas that have powerful cyclotrons, and that, unlike HEU-produced Mo-99, it does not benefit from favourable pricing.

The event’s final presentation was by Paola Panichelli of the Advanced Center Oncology Macerata (ACOM), on a potential replacement for Tc-99m. Panichelli discussed the radioisotope Cu-64, an isotope of copper that can also be produced by a cyclotron. Copper is naturally rich in the body’s brain and liver, and in cancer patients the metabolism of copper is altered, resulting in it concentrating in cancerous tissues. As the radiopharmaceutical Cu-64 chloride concentrates in tumours, it can be used to reveal the structure of the tumour and the cancer’s extent.

Panichelli emphasized why Cu-64 is so important: it decays by positron emission that allows its use for diagnostic imaging. Because it emits high energy beta minus particles, it can also be used for therapy, making it perfect for theranostic (therapy and diagnostic) applications. Research with Cu-64 chloride is still ongoing, and the European Medicines Agency is considering starting phase II clinical trials – testing on 100-300 patients – after initial studies have suggested it may be effective for diagnosing and treating prostate cancer and melanoma.

For now, the nuclear medical community is still heavily dependent on Tc-99m and a shortage in supply could adversely impact efforts to globally spread and increase the use of nuclear imaging techniques. The potential supply shortage of Mo-99 in the future poses a serious risk to Tc-99m, but the IAEA and its Member States are already looking ahead to avert a potential crisis and find alternative methods of production and effective substitute radioisotopes.

 

Last update: 04 Sep 2017

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