Neoadjuvant single-dose irradiation in low-risk breast cancer

The aim of this thesis is to assess whether single-dose partial breast irradiation before surgery could be used as a safe and effective treatment for low-risk breast cancer patients. The majority of low-risk breast cancer patients is currently treated with breast-conserving surgery followed by whole or partial breast irradiation in 15 doses. The current treatment leads to excellent oncologic outcomes, such as 10-year survival, but can also lead to toxicity, such as pain, and can worsen the performance status and quality of life. The main difference between the current treatment and the treatment investigated in this thesis is the timing of irradiation. We performed irradiation prior to surgery, meaning the tumor itself is treated, instead of possible residual tumor cells. This enables a smaller irradiated volume and a higher dose per fraction, leading to a single dose to give the necessary amount of irradiation. Breast-conserving surgery was performed six to eight months after irradiation to optimize the effect of irradiation on tumor destruction.
The pathway to performing this novel radiotherapy approach is described in this thesis, as well as the results of the treatment. Complete tumor destruction was observed in over 40% of the patients with only mild toxicity. We conclude that single-dose partial breast irradiation before breast-conserving surgery is a feasible treatment option for low-risk breast cancer patients. More research towards this treatment is necessary to enable accurate prediction of tumor destruction after single-dose irradiation. In which patient will complete tumor destruction be achieved, and might surgery be omitted?