New treatment of brain tumors in dogs: minimally invasive image-guided treatment by injection of radioactive holmium-166 microspheres

Experimental treatment 

Yearly 4 million people are diagnosed with a malignant brain tumor. The average life expectancy of these patients is less than a year. The number of patients that are yearly diagnosed with brain tumors and the life expectancy of these patients are comparable between humans and dogs. In addition, many similarities exist between the brain structure and tumor characteristics between humans and dogs. In both species, the current treatment options like surgery and radiation therapy rarely result in curation and these are often accompanied by significant side-effects.

A new minimally invasive treatment option for brain tumors has been developed subsidized by the Dutch Research Council and in collaboration between the Faculty of Veterinary Medicine at Utrecht University and the Radboud University Medical Center (Radboudumc) Nijmegen. This treatment option consists of neuro-navigated needle-injections of radioactive holmium microspheres into the tumor using image-guidance (MRI and CT). Using neuronavigation and image-guidance during the administration procedure ensures accurate administration of the microspheres into the tumor, which is essential in the treatment of brain tumors. With this minimally invasive treatment approach, the applied radiation dose in the tumor can be higher than conventional radiation therapy without damaging the surrounding or healthy tissue, thereby minimizing the potential side-effects.

The past years, dozens of dogs and cats with solid tumors (originating from bone, soft tissue and the oral cavity among others) were treated at the Small Animal Clinic Utrecht by intratumoral injection holmium microspheres. In most of the treated animals, a significant reduction of the tumor volume was observed accompanied by an increased life span and improved quality of life. These results led to the experimental treatment of humans with head and neck tumors in the University Medical Center Utrecht.  

In the current study at the Faculty of Veterinary Medicine at Utrecht University, we are investigating the feasibility and efficacy of this new minimally invasive treatment option using radioactive holmium microspheres to treat dogs with brain tumors. We aim to increase the life expectancy and quality of life. These results will also be used to develop a similar treatment option for human patients with brain tumors.

Patient inclusion

Dogs with a brain tumor are eligible to participate in this study, given that the prognosis without further treatment is low, there is no other viable treatment option available, or if you (the owner) chooses this treatment option over other therapies based on informed consent. 

Potentially eligible patients can be referred to the Small Animal Clinic Utrecht via their own veterinarian or specialized clinic. If the patient can participate in this study, most of the costs will be compensated by the research group.  


For more information you can contact Dr. Bas van Nimwegen by phone: 030-2539736, or by mail: You can also contact the surgical department ( or the reception of the Small Animal Clinic (030-2539411), a call-back request will then be sent to Dr. van Nimwegen.  

Illustration of a minimally invasive treatment technique for dogs with a brain tumor. This technique consists of targeted injections of radioactive holmium spheres into the tumor accompanied by CT or MRI scans.

The team

The described treatment option has become available through a collaboration between the Radboudumc Nijmegen, the Small Animal Clinic in Utrecht, and the Technical University Delft, and is funded by the Dutch Research Council (NWO). The treatment option is embedded within the UU Animal Cancer Centre, which is a collaboration between the departments of surgical oncology, medical oncology, medical imaging and pathology, with the aim to optimize our diagnosis and treatment of veterinary cancer patients.

More information can be found on the following websites