(UroToday.com)Androgen receptor-targeted agents represent one of the main treatment options for men with metastatic castrate-resistant prostate cancer (mCRPC). The addition of stereotactic radiation therapy to ablate metastatic foci may improve clinical outcomes in oligometastatic setting. The ARTO trial (NCT03449719) is a randomized phase II trial testing the benefit of upfront stereotactic body radiation therapy on all sites of metastatic disease in oligometastatic-mCRPC patients undergoing first-line therapy with abiraterone acetate. At the 2021 American Society of Clinical Oncology Genitourinary Cancers annual meeting (ASCO GU), Dr. Giulio Francolini and colleagues presented a preliminary analysis, reporting results after six months of follow up, together with an exploratory analysis of androgen receptor splice variants (ARV7/ARFL) PSA and PSMA expression on circulating tumor cells detected in this cohort of patients.

This trial enrolled31 patients with oligometastatic-mCRPC (defined as < 3 non-visceral metastatic lesions) that were randomized to receive first-line abiraterone therapy with or without stereotactic body radiation therapy on all metastatic sites. Baseline blood samples to detect circulating tumor cells and evaluate their ARV7, ARFL, PSA and PSMA expression were taken before the start of treatment with abiraterone acetate. Assessments comprehensive of clinical examination and serum PSA were performed every three months. Toxicity was assessed by the Common Terminology Criteria for Adverse Events toxicity scale (CTCAE v.4.03). The trial design for the ARTO trial is as follows:

There were13 patients enrolled in the treatment arm and 18 in the control arm. Overall, 19 metastatic lesions were treated with stereotactic body radiation therapy in the treatment arm. At 6 months, complete response (defined as a serum PSA level < 0.2 ng/dl) was achieved in 6 patients in the treatment arm versus 4 in the control arm, and biochemical response (defined as a PSA reduction > 50% if compared to baseline) was achieved in 10 patients in the treatment arm versus 8 in the control arm. One patient in the treatment arm died from other causes, and one biochemical progression occurred in the control arm. No adverse events occurred in both arms of treatment.

Circulating tumor cell analysis was available for 10 patients, out of whom 4 were found positive for circulating tumor cells (one and three from the treatment and control arm, respectively). ARV7 and ARFL were expressed in one patient from the control arm, and PSMA was expressed in all circulating tumor cell positive patients; PSA was expressed in two patients from the control and one from the treatment arm.

Dr. Fancolini concluded this talk describing preliminary results of the ARTO trial, with the following summary points:

Presented by:Giulio Francolini, MD, University of Florence, Florence, Italy; Radiotherapy Department, University of Florence, Florence, Italy

Co-Authors:Pietro Garlatti, Mauro Loi, Beatrice Detti, Michele Aquilano, Andrea Allegra, Barbara Guerrieri, Viola Salvestrini, Pamela Pinzani, Chiara Bellini, Francesca Salvianti, Giulia Stocchi, Lucia Pia Ciccone, Giulia Salvatore, Mariangela Sottili, Vanessa Di Cataldo, Isacco Desideri, Monica Mangoni, Icro Meattini, Lorenzo Livi; University of Florence, Florence, Italy; Radiotherapy Department, University of Florence, Florence, Italy; AOU Careggi, Firenze, Italy; Radiotherapy Unit, A.O.U. Careggi, Florence, Italy; University of Florence, Firenze, Italy; Radiotherapy Department, University of Florence, Firenze, Italy; Clinical Biochemistry and Clinical Molecular Biology Unit, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Florence, Italy; Radiotherapy Department, Universit di Firenze, Firenze, Italy; Radiotherapy Department, Florence, Italy; Department of a Biomedical, Experimental and Clinical Sciences "Mario Serio", Section of Radiation Oncology, University of Florence, Florence, Italy; Cyberknife Center, Istituto Fiorentino di Cura e Assistenza (IFCA), Firenze, Italy; Radiation Oncology Unit-Oncology Department, University of Florence, Florence, Italy

Written by:Zachary Klaassen, MD, MSc Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia,Twitter:@zklaassen_md during the2021 ASCO Genitourinary Cancers Symposium (ASCO GU), February 11th to 13th, 2021

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ASCO GU 2021: ARTO Trial: A Randomized Phase II Trial Enrolling Oligometastatic CRPC Patients Treated with ... - UroToday