(UroToday.com) The 2024 American Society for Radiation Oncology (ASTRO) annual meeting held in Washington D.C. was host to the session GU Quick Pitch (GU 4). Dr. Chia-Lin Tseng presented the results of a prospective trial exploring Post-Prostatectomy Linac-Based Ultrahypofractionated Radiotherapy for Patients with Localized Prostate Cancer: Toxicity and Quality-of Life Results.
Dr. Tseng began his presentation by stating that salvage radiation therapy (RT) post-prostatectomy 60-66 Gy in conventional fractionation is a well-accepted practice and supported by multiple randomized studies. (1) Moderately hypofractionated RT (52.5-62.5 Gy in 20-25 fractions) has been shown to be an acceptable practice standard. (2) Linac-based ultra hypofractionated RT is a treatment approach that utilizes a linear accelerator (linac) to deliver high doses of radiation in fewer fractions than conventional radiotherapy. Data from multiple studies suggest that prostate cancer may be more sensitive to higher doses per fraction of RT, aligning with the Stereotactic Body Radiotherapy (SBRT) paradigm. However, to date, there is limited data on SBRT in the early salvage post-prostatectomy setting.
- Eligibility Criteria:
- Undetectable PSA postoperatively
- Pathologic stage T3 or T4 (without residual disease)
- Positive surgical margins (R1)
- Postoperative detectable PSA (rising PSA on two consecutive measurements)
- Treatment Protocol:
- SBRT to the prostate bed: 30 Gy in 5 fractions, once weekly
- Optional SBRT to pelvic lymph nodes: 25 Gy in 5 fractions, once weekly
- Optional ADT: 6-24 months
The Primary endpoint of the study was acute genitourinary (GU) and gastrointestinal (GI) toxicities (≤3 months) using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0 and the secondary endpoints were late (≥6 months) GU and GI toxicities, acute and late GU and GI health-related quality of life (HRQoL) based on Expanded Prostate Cancer Index
Composite (EPIC) questionnaire.
The investigators recruited 30 patients for this prospective trial. Most participants had Grade Group 2 disease (53.3%) and 46.7% had positive surgical margins. Notably, 96.7% received post-operative SBRT in the salvage setting, while only 3.3% received it in the adjuvant setting. The median baseline PSA was 0.2 ng/mL. Elective nodal irradiation was performed in 53.3% of the patients, and 40% of the patients received ADT. The median follow-up period was 37.7 months (range 28.7-51 months).
No grade ≥3 acute GU or GI toxicities were documented. However, four late grade 3 toxicities were observed, including urinary incontinence in one patient and erectile dysfunction in three patients. During the acute period, 30% of the patients reported having GI Grade 2 toxicities, while only one (3.3%) had a Grade 2 GU toxicity. The complete CTCAE toxicity profile for the acute and late periods is shown in the table below:
In terms of HRQoL using the EPIC questionnaire, the investigators found that 8 patients (26.7%) reported acute moderate/severe Minimally Clinically Important Change (MCIC) in the urinary domain, 16 patients (53.3%) in the bowel domain, and 3 patients (10.0%) in the sexual domain. Moreover, 2 patients (6.7%) reported late moderate/severe MCIC in the urinary domain, 3 patients (10.0%) in the bowel domain, and 3 patients (10.0%) in the sexual domain.
Dr Tseng wrapped up his presentation with the following remarks:
- Post-prostatectomy SBRT to the prostate bed, with or without elective nodal irradiation, is well tolerated.
- In this prospective study of 30 patients, there were no grade ≥3 acute toxicities, and the impact on health-related quality of life in the acute period was minimal.
- However, the median follow-up was 37.7 months, and further follow-up is warranted to better evaluate long-term toxicity, biochemical disease-free survival, and patterns of failure for this treatment modality in the post-prostatectomy space.
- A multicenter expanded cohort has completed accrual to gain broader experience and more robust safety and efficacy data for this treatment modality.
Presented by: Chia-Lin Tseng, MD, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
Written by: Julian Chavarriaga, MD – Society of Urologic Oncology (SUO) Clinical Fellow at The University of Toronto, @chavarriagaj on Twitter during the 2024 American Society for Radiation Oncology (ASTRO) annual meeting held in Washington D.C., between the 29th of September and the 2nd of October.
References:- Vale CL, Fisher D, Kneebone A, Parker C, Pearse M, Richaud P, Sargos P, Sydes MR, Brawley C, Brihoum M, Brown C, Chabaud S, Cook A, Forcat S, Fraser-Browne C, Latorzeff I, Parmar MKB, Tierney JF; ARTISTIC Meta-analysis Group. Adjuvant or early salvage radiotherapy for the treatment of localised and locally advanced prostate cancer: a prospectively planned systematic review and meta-analysis of aggregate data. Lancet. 2020 Oct 31;396(10260):1422-1431. doi: 10.1016/S0140-6736(20)31952-8. Epub 2020 Sep 28. PMID: 33002431; PMCID: PMC7611137.
- Castelluccia A, Tramacere F, Colciago RR, Borgia M, Sallustio A, Proto T, Portaluri M, Arcangeli PS. 10-yr Results of Moderately Hypofractionated Postoperative Radiotherapy for Prostate Cancer Focused on Treatment Related Toxicity. Clin Genitourin Cancer. 2024 Aug;22(4):102102. doi: 10.1016/j.clgc.2024.102102. Epub 2024 Apr 24. PMID: 38759337.