Background and purpose: Among different cancers, breast cancer has a high prevalence among women and radiotherapy is used as a treatment modality in which radio sensitizers are used to increase its efficiency. Nanoparticles are such sensitizers that enhance the efficiency of radiotherapy via creation of free radicals and induction of oxidative stress. This study aimed at evaluating the synergistic effect of radiation therapy and TiO₂ nanoparticles on animal models of breast cancer.

Materials and methods: After induction of breast adenocarcinoma tumors in Balb/C, the animals were divided into several groups as control, rutile and anatase injections at 5mg/kg and 10mg/kg doses/with and without radiotherapy. Then, the efficiency of treatment was evaluated. 

Results: In groups receiving anatase nanoparticles with and without radiation, the values for tumor volume, relative volume and relative volume percentage showed a small increase and a considerable reduction, respectively. In rutile groups with and without radiation, these values showed a small increase and a considerable increase, respectively. IR value reduced to negative value and then increased to zero and positive in anatase groups with and without radiation. This parameter had little changes in rutile groups with and without radiation.

Conclusion: Titanium dioxide nanoparticles increased sensitivity of tumor cells to radiation therapy due to ROS production. Compared with rutile crystals, anatase crystals have intense effect because of having a larger surface area and higher photocatalytic activity.