Para-Aortic Radiation Therapy for Oligorecurrent Prostate Cancer.

Oligorecurrent prostate cancer limited to the pelvic lymph nodes (LNs) can be treated with whole pelvis radiotherapy. Radiotherapy may also be beneficial for oligorecurrent prostate cancer in the para-aortic (PA) LNs.

We identified a sequential cohort of patients with oligorecurrent prostate cancer to the PA LNs (≤5) treated with elective, conventionally fractionated PA radiotherapy (PA-RT) plus simultaneous integrated boost (SIB) to LN+ disease at our institution from 2015 to 2021. The primary endpoint was progression-free survival (PFS) at 2 years using Kaplan-Meier estimation. PFS was defined as the time from PA-RT to the first event: biochemical failure (PSA 50% above post-treatment nadir and at least 4 ng/mL), escalation of therapy, radiological progression, or death. Secondary endpoints included 2-year biochemical failure-free survival (BFFS), 2-year overall survival (OS) and treatment-related toxicity.

Thirty-four patients were included (median age 66 years), and 82.4% were status post-prostatectomy. The median time from diagnosis to PA-RT was 5.7 years. The median PSA at PA-RT was 3.15 ng/mL (IQR 1.30-5.90). All patients were treated to the PA region with 45-50 Gy in 25 daily fractions. LN+ disease received a SIB to a median dose of 62.5 Gy (range 60-65 Gy). Most received photon-based RT, while 21.1% were treated with proton therapy. Nearly all (97.1%) patients had androgen deprivation therapy (ADT) and 52.9% abiraterone. The median follow-up time from PA-RT was 21.5 months. PFS at 2-years was 83.4% (95% CI: 68.6-100%). Two-year BFFS was 90.4% and OS 100%. There were no grade 3 or higher acute toxicities. There were 10 (29.4%) grade 2 acute toxicities. There were two (5.9%) grade 3 chronic toxicities and 4 (11.8%) chronic grade 2 toxicities.

PA-RT for oligorecurrent prostate cancer has low toxicity with very encouraging early disease control. These preliminary results require validation in prospective studies.

International journal of radiation oncology, biology, physics. 2022 Jun 04 [Epub ahead of print]

Benjamin J Rich, Chris Montoya, William H Jin, Benjamin O Spieler, Brandon A Mahal, Rodrigo Delgadillo, Marijo Bilusic, Matthew C Abramowitz, Alan Pollack, Alan Dal Pra

Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine. Electronic address: ., Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine., Department of Hematology/Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine., Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine. Electronic address: .

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