Abiraterone Acetate (AA) and stereotactic body radiotherapy (SBRT) were evaluated in the multicenter, randomized phase II study ARTO for treating patients with oligometastatic castrate-resistant prostate cancer. For a study, researchers sought to offer preliminary findings about the biochemical response 6 months following the commencement of therapy.

Almost less or around 3 non-visceral metastatic lesions, or oligometastatic CRPC, were randomly assigned to receive either I line systemic therapy alone (abiraterone acetate, the control arm) or I line systemic treatment in combination with concurrent SBRT on all metastatic sites of illness. Metastatic CRPC treatments from the past were not permitted. Both were allowed for traditional staging and methabolic imaging (e.g., choline or PSMA PET/CT). SBRT should be given when there is at least a BED<sub style=”vertical-align: sub;”>3</sub>≥ 100. The objectives of the current investigation were the complete biochemical response (CBR, defined as PSA 0.2≤ ng/ml at 6 months after therapy) and the biochemical response at 6 months after treatment began.

The ARTO study had 114 patients, also included in the current analysis. A CBR was present in 38.6% of cases overall (control arm: 27.6%, experimental arm: 50%). After adjusting for baseline PSA, patients receiving SBRT had a substantially higher OR for CBR, with an OR of 2.58 (95% CI 1.16-5.76, P-value 0.021). The patients in the experimental arm also had significantly reduced PSA levels at 6 months, according to a linear regression model (P=0.004).

When compared to systemic therapy with abiraterone acetate alone, SBRT dramatically improved biochemical response in patients with I-line metastatic CRPC.

Reference: annalsofoncology.org/article/S0923-7534(22)03352-X/fulltext