ESTRO 2024 - Abstract Book

S2418

Clinical - Urology

ESTRO 2024

1 IRCCS San Raffaele Hospital, Radiation Oncology, Milan, Italy. 2 IRCCS San Raffaele Hospital, Medical Physics, Milan, Italy. 3 Vita e salute Unoversity, Medicine and surgery, Milan, Italy

Purpose/Objective:

To retrospectively evaluate the role of Stereotactic Radiotherapy (SRT) as Metastasis-Directed Therapy (MDT) in patients (pts) with oligoprogressive metastatic Castration-Resistant Prostate Cancer (mCRPC), undergoing Androgen Receptor Target Agents (ARTA) therapy in our institution.

Material/Methods:

From August 2015 to January 2023 62 oligoprogressive lesions in 24 mCRPC patients undergoing ARTA therapy (Abiraterone Acetate or Enzalutamide) were treated with MTD. SRT was delivered using Cyberknife® (N= 41 lesions), TomoTherapy® (N=20) or RapidArc ™ (N=1). A median biologically equivalent dose (BED) of 103 Gy (range 46-216, considering α/β = 3) was prescribed. Sixteen pts were treated with Abiraterone (ABI) and eight with Enzalutamide (ENZA). Primary end-points were time to Next Systemic Therapy (NEST) and Overall Survival (OS). Side-effects were assessed according to Common Terminology Criteria for Adverse Events v5.0.

Results:

Median follow-up after RT was 21.5 months (range 4.6-58.5). Ten pts continued ARTA, while 14 pts switched to systemic therapy. All other pts completed SRT and no ≥G2 side effects were registered. Local recurrence was observed in five pts, while the other pts presented distant metastasis. Median time to NEST was 13.8 (range 2.5 58.5) months. Six-, 12 and 24-month NEST-free survival were 72.4%, 59%, 45.2%, respectively, without a significant difference between pts treated with ABI vs ENZA (p=0.30). One-, 3- and 5-year OS from the end of SRT was 98.4%, 86.7%, 44.2% respectively.

Conclusion:

SRT as MDT, in patients with oligoprogressive mCRPC, is well-tolerated and prolong the efficacy of the ongoing systemic treatment, positively affecting disease progression and postponing the transition to a subsequent line of treatment, which is not always effective, by more than one year, with good OS results from mCRPC diagnosis. Prospective trials are awaited to confirm these results.

Keywords: Prostate, ARTA, castration resistent

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Risk-adapted dose intensification prostate SBRT: preliminary results on control, toxicity and QoL