Multi-Center Trial of Stereotactic Body Radiotherapy for Low- and Intermediate-Risk Prostate Cancer : Survival and Toxicity Endpoints
Mené sur 309 patients atteints d'un adénocarcinome de la prostate à risque faible ou intermédiaire de récidive (durée médiane de suivi : 61 mois), cet essai multicentrique évalue l'efficacité, du point de vue de la survie sans maladie et de la survie globale actuarielle à 5 ans, et la toxicité d'une radiothérapie corporelle stéréotaxique avec escalade de dose
Purpose : The radiobiology of prostate cancer may favor the extreme hypofractionation inherent in stereotactic body radiotherapy (SBRT), however data from a large, multi-center study are lacking. We therefore examine the hypotheses that dose-escalated SBRT can be safely administered across multiple institutions, with favorable 5-year disease-free survival (DFS) rates compared to historic controls. Methods and Materials : Twenty-one centers enrolled 309 patients with prostate adenocarcinoma: 172 with low-risk (LR), and 137 with intermediate-risk (IR) disease. All were treated with a non-coplanar robotic SBRT platform using real-time tracking of implanted fiducials. The prostate was prescribed 40 Gy in 5 fractions of 8 Gy. Toxicities were assessed using CTCAE v3, and biochemical failure using the nadir+2 definition. Study populations yielded 90% power to identify excessive (>10%) rates of grade 3+ genitourinary (GU) or gastrointestinal (GI) toxicities, and in the LR group, 80% power to show superiority in DFS over a 93% historic comparison rate. Results : At 61 months median follow up, two LR patients (1.2%) and two IR patients (1.5%) experienced grade 3 GU toxicities, far below the 10% toxicity rate deemed excessive (upper limits of 95% CI 3.5% and 4.3%, respectively). There were no grade 4-5 toxicities. All grade 3 toxicities were GU, occurring 11-51 months after treatment. For the entire group, actuarial 5-year overall survival was 95.6%, and DFS was 97.1%. The 5-year DFS was 97.3% in LR patients (superior to 93% DFS from historic controls, p=0.0008, lower limit of 95% CI 94.6%) and 97.1% for IR patients. Conclusions : Dose-escalated prostate SBRT was administered with minimal toxicity in this multi-institutional study. Relapse rates compare favorably to historical controls. SBRT is a suitable option for low- and intermediate-risk prostate cancer.
https://www.redjournal.org/article/S0360-3016(18)30891-5/fulltext