Stereotactic Ablative Radiotherapy (SAbR) for Primary Prostate Cancer

Prostate cancer (PCa) is the most common solid tumor among US men. Its burden on patients and healthcare systems has risen sharply (Ellinger J, EPMA J 13:1–7, 2022), driven by prolonged costs of treating advanced disease states and by treatment-related impact on quality of life (Donovan JL, N Engl J Med 375:1425–1437, 2016). In localized PCa, radical prostatectomy (RP) and radiotherapy (RT) are equally recognized standards of care (Hamdy FC, N Engl J Med 388:1547–1558, 2023), leaving a clear mandate for innovations to focus on reducing treatment toxicity and logistics impact. For RT, exploration of ultra-hypofractionated radiotherapy (UHRT) to reduce treatment visits dates back over 60 years (Lloyd-Davies RW, et al., Urology 36:107–11, 1990). Since then, a multitude of technological advances and an evolution in understanding of PCa radiobiology that support UHRT have coalesced under the paradigm of stereotactic ablative body radiotherapy (SAbR), also referred to as stereotactic body radiotherapy (SBRT). Robust testing of SAbR in clinical investigations has now led to its recognition as a safe, effective, and convenient standard treatment in PCa for a wide spectrum of patients, from localized to advanced settings. Building upon this are a large array of ongoing studies that seek to leverage SAbR and advanced imaging to deliver treatments tailored to an individual patient’s disease, toxicity risks, and preferences. At the same time, with rapid uptake of SAbR in recent years (Qureshy SA, et al., JAMA Netw Open 6:e2337165, 2023 and Mahase SS, et al., JAMA Netw Open 3:e1920471, 2020), it is important to emphasize persisting gaps in knowledge and a need for careful investigation and implementation. In this chapter, we will review the development, relevant literature, techniques, and future directions for SAbR in primary prostate cancer.