The use of prostate radiotherapy (RT) is unclear in men with metastatic hormone-sensitive prostate cancer (mHSPC) receiving androgen deprivation therapy (ADT) and androgen receptor-pathway inhibitors. The EAU guidelines recommend offering ADT combined with prostate RT (using doses up to the equivalent of 72 Gy in 2 Gy fractions) to patients whose first presentation is metastatic disease and who have low-volume disease per CHAARTED criteria.1 The PEACE-1 study aimed to examine the efficacy and safety of adding prostate RT to patients with de novo mHSPC who receive intensified treatment with ADT, docetaxel and abiraterone.2
METHODS
The multi-centre, open-label, phase III PEACE-1 study with a 2 x 2 factorial design randomised 1,172 patients with de novo mHSPC to receive standard of care (SOC, i.e. ADT ± docetaxel), SOC plus abiraterone, SOC plus RT (74 Gy in 37 fractions to the prostate), or SOC plus RT plus abiraterone. The coprimary endpoints were radiographic progression-free survival (rPFS) and overall survival (OS), analysed by intention-to-treat in patients with low-volume metastatic disease and in the overall study population.
RESULTS
For rPFS, a qualitative interaction was observed between RT and abiraterone in the population of patients with low-volume disease, preventing the pooling of intervention groups for analysis. For OS, this interaction was not seen, and therefore the two intervention groups receiving RT were pooled together for analysis. At a median follow-up of 6 years, the addition of RT to SOC improved rPFS in patients with low-volume disease treated with abiraterone (median 4.4 years in the SOC plus abiraterone group versus 7.5 years in the SOC plus RT plus abiraterone group; aHR[99.9% CI]: 0.65[0.36-1.19], p= 0.0019). This rPFS benefit was not seen in patients not treated with abiraterone (median 3.0 years in the SOC group versus 2.6 years in the SOC plus RT group; HR[99.9% CI]: 1.08[0.65-1.80], p= 0.61). In patients with low-volume disease, the addition of RT did not impact OS (median 6.9 years for SOC ± abiraterone versus 7.5 years for SOC + RT ± abiraterone; HR[95.1% CI]: 0.98[0.74-1.28], p= 0.86). RT reduced the occurrence of serious genitourinary events, regardless of metastatic burden and without increasing the overall toxicity.
CONCLUSIONS
Based on the PEACE-1 trial, combining RT with SOC plus abiraterone improves rPFS but not OS in patients with low-volume de novo mHSPC. In addition, RT reduces the occurrence of serious genitourinary events, regardless of metastatic burden.
References
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