Why does androgen deprivation enhance the results of radiation therapy?

The role of androgen deprivation therapy (ADT) has been explored in combination with surgery, brachytherapy, and external beam radiotherapy with the goal of improving local control and overall survival. Multiple cooperative groups' studies strongly support the use of neoadjuvant ADT treated with definitive external beam radiotherapy. Neoadjuvant androgen deprivation improves intraprostatic local control with external beam radiotherapy and reduces the second wave of distant metastases. Neoadjuvant androgen deprivation achieves this endpoint through "sensitization" of the tumor to radiation and through improved oxygenation. However, the use of neoadjuvant ADT before radical prostatectomy and brachytherapy is controversial. There are ongoing clinical trials that will hopefully better define patient populations that will benefit from hormonal deprivation therapy.