Hypofractionated radiation therapy involves the delivery of higher doses of radiation over a smaller number of treatment sessions, compared to conventional radiation therapy which requires a substantially longer course of treatment. SBRT uses advanced techniques to deliver ultra-hypofractionated radiation therapy — very high doses of radiation are administered over several days. This treatment process necessitates an extremely high degree of accuracy and precision. The CyberKnife System, designed to deliver SBRT, is the only radiotherapy device that can maintain sub-millimetric accuracy with continual imaging and automatic beam delivery corrections, including rotation, throughout treatment delivery, making it easier for clinicians to effectively treat patients while minimizing dose to healthy tissue.
"Men diagnosed with recurrent prostate cancer after previous radiation therapy have few treatment choices. Most, if treated, receive only ADT which has the potential for long-lasting 'whole body' side effects while rarely eradicating the tumor completely," said Donald B. Fuller, M.D., at Genesis Healthcare Partners in San Diego, California and lead investigator of the study. "This study demonstrates that prostate SBRT delivered using the CyberKnife System offers a viable, non-invasive option for an underserved patient population and most typically delays the need for ADT for greater than five years, which would provide substantial quality of life benefits. From a technology viewpoint, the inherent sub-millimeter accuracy of the CyberKnife System due to its highly unique tracking method was critical to the success and safety of this protocol, allowing the dose to be delivered to the prostate with no additional expansion of the target volume."
Study Highlights
The study titled, "Retreatment for Local Recurrence of Prostatic Carcinoma After Prior Therapeutic Irradiation: Efficacy and Toxicity of HDR-Like SBRT," evaluated 50 patients with biopsy-proven recurrent prostate cancer diagnosed at least two years after initial treatment. Forty-three patients had previously received treatment with conventionally fractionated radiation therapy and seven patients had received treatment with another method (five brachytherapy, one SBRT and one radical prostatectomy followed by post-prostate bed salvage radiation therapy). This study demonstrated:
- At five years, the disease-free survival (DFS) rate was 60 percent, indicating patients experienced no signs or symptoms of their cancer over that time period. This rate is within the reported range for salvage brachytherapy and comparable to reported salvage radical prostatectomy results, but without the need for hospitalization, anesthesia, and long recovery times typically associated with these treatments;
- The median prostate specific antigen (PSA) decreased to 0.16 ng/mL at five years, similar to initial treatment with brachytherapy and lower than typical conventional fractionation, based on results from other studies;
- No grade two or higher gastrointestinal (GI) events were reported. Genitourinary (GU) toxicity was lower than reported rates for salvage radical prostatectomy and seems less frequent after prior standard external radiation treatment.
"This study is significant because it highlights a potential new option for extending symptom-free survival in men with locally recurrent prostate cancer previously treated with radiation therapy," said Fabienne Hirigoyenberry-Lanson, Ph.D., vice president global medical and scientific affairs, at Accuray."The data reinforces the benefits of the CyberKnife® System's robotic design and motion synchronization capabilities and show why CyberKnife prostate SBRT is becoming the treatment of choice by clinicians who want a high precision, versatile and non-invasive option that provides excellent disease control with minimal side effects."
References:
- "Hormone Therapy For Prostate Cancer Fact Sheet". 2020. National Cancer Institute.