Comparison of before (left) and after therapy shows disappearance of tumours (shown as dark spots) from the liver. Note: tumours in the kidneys are not affected. (Photos: Frank Nijsen, UMC Utrecht)
Terminal liver cancer patients have received an experimental radiotherapy involving highly radioactive microspheres at the Utrecht Medical Centre. At sufficient doses, the liver tumours were eradicated while side effects proved minimal.
Researchers at the Reactor Institute Delft played an important role in developing the optimal radiation method for the poly-lactate covered holmium microspheres. Delivering sufficient dosages without overheating or damaging the spheres proved to be challenging, however. During the clinical trial, the RID routinely radiated holmium spheres in response to requests from medical biologist, Dr Frank Nijsen, and head of radio pharmacy, Dr Fred van het Schip (UMC Utrecht). One time, when Dr Menno Blaauw, a RID researcher involved in the holmium project, couldn’t help wondering how the patient fared after the treatment, he phoned his UMC contact, who replied that he didn’t know, as the patient had just left for a skiing holiday.
Fifteen terminal colon cancer patients have been treated over the last year in this first phase clinical trial. The trial is meant to establish that the treatment is safe and to screen for adverse effects – not to determine the effectiveness. Nonetheless, a remarkable reduction of liver tumours has been established at large enough doses. The treatment consists of two consecutive arterial injections of holmium spheres, a few hours apart. The first injection involves a low dose to check if the holmium particles reach the tumour, the whole tumour and nothing but the tumour. The holmium whereabouts can be traced with a gamma camera, since the particles emit gamma radiation (which is detectable outside the body) as well as beta radiation (high-energy electrons which kill cells in the direct vicinity of the blood vessels). The diameter of the particles (30 micrometre) is chosen so that the microspheres will get stuck in the capillaries to release their radiation charge at the spot. When the first shot indicates the blood vessel is leading only to the tumour, a second shot will be delivered which delivers over 100 Gray of radiation locally. “Over 100 Gray, everything is dead”, Blaauw resumes. “It’s the same dose they use for sterilisation.” Despite the locally lethal dose, the patients seem to suffer only mild nausea in the first day after treatment. After that, they generally feel fine.
Next, a larger phase II clinical trial will be held to test the treatment’s effect and to establish the protocol. If – and it’s still a big if – the researchers succeed in effectively targeting only the tumour and avoid spilling radiation to other organs, holmium therapy may develop into an effective and patient-friendly form of radiotherapy for tumours that have suitable vascular structures.
