Particle Therapy 2017

Normal tissue effects

Therapeutic Ratio

If α⁄β ratio of tumor is the same or less than that of the critical normal tissue , then a larger dose per fraction (hypofractionation) is preferred i.e., prostate cancer, breast cancer If α⁄β ratio of tumor is high (often 10 or greater) and > α⁄β ratio of normal tissue (often < 5) a lower dose per fraction is preferred i.e., squamous cancer of head and neck

Horiot J., Radiother Oncol 25: 231-241, 1992

Brenner D., IJROBP 57: 912-914, 2003