Intra-tumoral holmium-166 therapy: Feasibility in head and neck cancer

Head and neck cancer (HNC) has a high incidence, the prognosis in case of advanced stage disease is poor, and over the past decades, the overall survival has only slightly increased. This thesis, provide insight into the feasibility and application of intra-tumoral treatment with 166Ho-microspheres in HNC. After reviewing the scientific literature, which indicated that this form of treatment is relatively safe and effective and can have additional value for patients. Stability was investigated in patients treated by 166Ho-microspheres radioembolization. In patients with liver tumors it was shown that the measured content of 166Ho in blood and urine was low which implied the stability. Subsequently, the intra-tumoral treatment in veterinary and human patients was described. Promising results were obtained in veterinary patients with a local response of 55%. In the human patients no adverse events occurred. However, technical difficulties, resulted in a relatively small area with sufficiently high local dose, while a large part of the tumor was left untreated. Therefore, improvements in the combination of injection solution, administration system and image guided treatment to improve the distribution of microspheres are desired. Finally, the potential of CT and dual energy CT (DECT) was explored. CT imaging provided superior resolution (<1 mm) compared to the currently used SPECT (4.8 mm) and MRI (3 mm). DECT, provided excellent accuracy for concentrations down to 0.125 mg/mL compared to 2.6 mg/mL with conventional CT. This thesis shows that the innovative image-guided intra-tumoral treatment of radioactive 166Ho-microspheres is a promising and relatively safe treatment approach in patients with head-and-neck tumors.