ASCO 2023

Benefits of radiotherapy combined with abiraterone and standard therapy in poorly metastatic prostate cancer

One year after delivering its first highly conclusive results, the PEACE-1 multicenter trial, promoted by Unicancer and coordinated by Gustave Roussy, shows that the combination of prostate radiotherapy with abiraterone (a new-generation hormone therapy) and standard treatment, improves progression-free radiological survival for patients with poorly metastatic prostate cancer. The results of this new analysis, presented at ASCO, indicate that this "triple therapy" could become the first-line treatment for these patients.

Abstract no. 5000 orally presented by Dr. Alberto Bossi on Sunday, June 4

An international, multicenter Phase 3 trial, the PEACE-1 study, enrolled 1 172 patients with metastatic prostate cancer between 2013 and 2018.

After random selection, patients were divided into four groups : a first "control" group received standard treatment (androgen suppression alone or combined with docetaxel chemotherapy), the second received standard treatment and abiraterone (a second-generation hormone therapy), the third group was given standard treatment and prostate radiotherapy, while the fourth received standard treatment, abiraterone and radiotherapy. All patients had a median follow-up of 6.1 years. The PEACE-1 endpoints were overall survival and radiological progression-free survival.

The initial results of the PEACE-1 trial, published last year, demonstrated that combining abiraterone with standard therapy improved both progression-free and overall survival.

Benefits in terms of progression-free survival and low toxicity

The new PEACE-1 analysis, presented this year at ASCO, was designed to assess the contribution of radiotherapy to standard treatment and abiraterone. « This analysis preferentially targeted prostate cancer patients with a low metastatic load - three bone metastases or less. Indeed, an English study had shown that if there is any benefit from radiotherapy in metastatic prostate cancer, it is restricted to patients with few metastases. We therefore hypothesized that it was in this group of patients that radiotherapy could have the greatest impact in combination with abiraterone », explains Professor Karim Fizazi, head of Gustave Roussy's genitourinary committee and coordinator of PEACE-1.

The results show that when combined with standard treatment, radiotherapy has the same effects as standard treatment alone. However, when combined with abiraterone and standard treatment, the benefit is significant, with an improvement in radiological progression-free survival of 7.5 years, versus 4.4 years for the standard/abiraterone combination.

Among other effects observed, radiotherapy can prevent serious urological complications in patients with metastases, in particular urinary retention due to urethral compression, requiring a urinary catheter or even nephrostomy, or pain and bleeding necessitating resection surgery or irradiation. Combined with abiraterone, preventive radiotherapy reduces the frequency of these complications.

« This is the first time that an improvement in radiological progression-free survival with standard treatment plus abiraterone and radiotherapy has been demonstrated for these patients, » says Professor Karim Fizazi. The treatment was also well tolerated, with very few radiotherapy-related side effects. Less than 1% of patients experienced rectal bleeding.

« This Phase 3 trial shows that reasonable management of patients with low-grade metastatic prostate cancer most often involves at least a triple combination of standard treatment, abiraterone and radiotherapy, » concludes Professor Karim Fizazi.

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