Toxicity and early findings in a post-prostatectomy ablative radiation therapy multicentric trial
PO-1452
Abstract
Toxicity and early findings in a post-prostatectomy ablative radiation therapy multicentric trial
Authors: Raffaella Lucchini1, Ciro Franzese2, Suela Vukcaj3, Giorgio Purrello1, Denis Panizza4, Valeria Faccenda4, Stefano Andreoli5, Gian Luca Poli5, Davide Baldaccini2, Lorenzo Lo Faro2, Stefano Tomatis2, Luigi Franco Cazzaniga3, Marta Scorsetti2, Stefano Arcangeli1
1University of Milan Bicocca, Radiation Oncology Department, Milan, Italy; 2Humanitas Clinical and Research Center - IRCCS, Department of Radiotherapy and Radiosurgery, Rozzano, Italy; 3ASST Papa Giovanni XXIII, Department of Radiation Oncology, Bergamo, Italy; 4ASST Monza, Medical Physics Department, Monza, Italy; 5ASST Papa Giovanni XXIII, Department of Medical Physics, Bergamo, Italy
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Purpose or Objective
To investigate the feasibility of ultrahypofractionated radiotherapy to prostate bed in patients with biochemical and/or clinical relapse following radical prostatectomy enrolled in the prospective observational multicentric POPART trial (NCT04831970).
Material and Methods
Patients with post-radical prostatectomy PSA level of ≥ 0.1-2.0 ng/mL or local relapse at PSMA PET CT or multiparametric MRI were treated with Linac-based Volumetric Modulated Arc Therapy (VMAT) on prostate bed up to a total dose of 32.5 Gy in five fractions every other day (EQD21.5 = 74.2 Gy). Androgen deprivation therapy (ADT) was allowed at physician’s discretion. Maximum acute toxicity was assessed with Common Terminology Criteria for Adverse Events version 5 (CTCAE_v5) scale. In addition, International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) score was used at baseline and during the follow-up.
Results
From April 2021 to June 2022 thirty men with a median age of 72 years (range 55-82) were enrolled in three Italian centres. The majority of them (74%) had a biochemical relapse only, while 8 patients (26%) had a local relapse. Median time from prostatectomy was 54.5 months (range 7-155). Median PSA level before RT was 0.30 ng/ml (range 0.18-1.89 ng/ml). Four patients (13%) received ADT. At baseline median ICIQ-SF score was 1 (range 0-8). The median PTV was 72 cc (range 14.8-250.2 cc). No treatment interruptions were registered. After SBRT completion only one instance of Grade 2 acute gastrointestinal (GI) toxicity was documented; no ≥ Grade 2 acute genitourinary (GU) toxicity was observed, and 3 patients experienced Grade 1 GU side effects. At three months follow-up no GI and ≥ 2 GU side effects were reported; Grade 1 GU toxicity was detected in 3 patients (10%). No changes in ICIQ-SF were assessed. Three months after SBRT all but two patients, who progressed distantly, were found biochemically controlled with a median post-treatment PSA level of 0.07 ng/ml (range 0-0.48 ng/ml).
Conclusion
Post-prostatectomy ablative radiation therapy for biochemical and/or clinical relapse allowed a convenient and safe treatment with negligible early side effects, showing that high focused radiation in few fractions to the prostate bed with robust conformality and modulation, abrupt dose fall off and image guidance can be extended to the postoperative setting. Long term results are needed to confirm these findings.