SABR in high risk prostate cancer: outcomes from two prospective clinical trials with and without elective nodal irradiation
Menée à partir des données de deux essais cliniques de phase II portant au total sur 60 patients atteints d'un cancer de la prostate à haut risque de récidive (durée médiane de suivi : 5,6 ans ou 4 ans selon l'essai), cette étude évalue l'efficacité, du point de vue du contrôle biochimique, d'une radiothérapie stéréotaxique ablative avec ou sans irradiation ganglionnaire élective
Purpose : There is limited data on SABR in high-risk prostate cancer (PCa) especially regarding the role of elective nodal irradiation (ENI). This study compares two prospective phase II trials using SABR in high-risk prostate cancer, with and without ENI. Methods : Patients had high-risk PCa. Trial1 received 40Gy/5 to the prostate and 30Gy/5 to the seminal vesicles. Trial2 received 40Gy/5 to the prostate and 25Gy/5 to the pelvis and seminal vesicles. CTCAE toxicities were collected. Biochemical failure (BF) was defined as nadir+2 and 4-year PSA response rate (4yPSARR) was < 0.4 ng/ml. Results : 60 patients were included (trial1, n=30; trial2, n=30). Median follow-up was 5.6y and 4.0y. Median nPSA was 0.02ng/ml for both. Six patients had BF, all from trial1. The BF rate was 14.6% at 5y in trial1and 0% in trial2. 63% of patients in trial1 and 93% in trial2 had a 4yPSARR. Two patients died in trial1, one from metastatic disease. One patient in trial2 died from other causes. No other patients developed metastatic disease, and one patient in trial1 had CRPC. OS at 5y was 93.2% and 96.7% (p=0.86). There was significantly worse late GI and sexual toxicity in trial1, but no difference in late GU toxicity. Conclusions : SABR in high-risk prostate cancer yields biochemical control rates that may be comparable to other radiotherapy modalities. ENI using SABR is feasible and may lead to a significant improvement in biochemical control as well as in 4yPSARR, without an increase in late GI or GU toxicity. Longer follow-up would provide a better assessment of biochemical control. Well conducted phase III trials are needed to fully establish the role of SABR as well as ENI in high-risk prostate cancer.