Our recently published study represents the largest Spanish multicenter analysis to date evaluating acute toxicity following SBRT for localized prostate cancer. We retrospectively analyzed 251 patients treated across 12 GenesisCare centers in Spain between 2020 and 2023. The majority of patients had intermediate-risk disease (66.5%), with 30.3% classified as low/very low risk, and only 3.2% as high/very high risk. All patients received SBRT in 5 fractions (35–40 Gy) on alternate days, with near-universal use of rectal spacers (99.2%) and fiducial-based image guidance.
Acute grade ≥2 genitourinary (GU) toxicity occurred in only 6.8% of patients, gastrointestinal (GI) toxicity in 0.8%, and sexual toxicity in 12.4%. These results are comparable to or better than those reported in clinical trials, likely reflecting a combination of careful patient selection (e.g., low baseline IPSS scores in >50% of patients) and modern techniques such as rectal spacer placement and reduced prostate–rectum margins.
Regarding radiotherapy delivery platforms, most patients (83.7%) were treated using Volumetric Modulated Arc Therapy (VMAT) with conventional linear accelerators, followed by helical tomotherapy (9.6%) and non-coplanar robotic SBRT with CyberKnife (6.8%). This distribution reflects both technological availability across centers and clinical decision-making based on prostate volume, proximity to organs at risk, and logistical considerations. While direct comparative data between platforms remain limited, current evidence supports the safety and efficacy of SBRT for prostate cancer regardless of the system used, provided that high standards in treatment planning, immobilization, and image guidance are maintained. Our multicenter experience underscores the feasibility of delivering high-quality SBRT across diverse technologies (Figure 1), highlighting its adaptability to a wide range of clinical environments.
Interestingly, in multivariable analysis, androgen deprivation therapy (ADT) was significantly associated with an increased risk of sexual toxicity. Moreover, a dose of 40 Gy was associated with lower GU toxicity compared to 36.25 Gy when treating both the prostate and seminal vesicles, potentially due to improved dosimetric distribution in lower-volume prostates.
While the retrospective design and lack of standardized patient-reported outcomes are acknowledged limitations, our study reinforces the excellent acute toxicity profile of SBRT in localized prostate cancer and supports its adoption as a standard-of-care option across various clinical scenarios.
We hope these findings contribute to the ongoing effort to optimize and personalize prostate cancer radiotherapy, minimizing toxicity while maintaining therapeutic efficacy.
Figure 1. Axial CT Slice of the SBRT Treatment Plan for Localized Prostate Cancer.
Colorwash dose distribution is displayed, ranging from 0.0 cGy to 3918.9 cGy, as indicated on the left scale. Green areas represent dose levels around 2000 cGy, while red corresponds to the highest dose regions near the prescription level. The planning target volume (PTV) is centrally located. Organs at risk are contoured: rectum (orange), bladder (blue), and femoral heads (light blue).
Written by: Sigfredo E. Romero Zoghbi, MD, Department of Radiation Oncology, GenesisCare Talavera de la Reina, Spain; Research and Doctorate School, Universidad Europea de Madrid, Spain
Read the Abstract