Para-Aortic Radiation Therapy for Oligorecurrent Prostate Cancer

• Published in: International journal of radiation oncology, biology, physics Vol. 114; no. 4; pp. 718 - 724
• Main Authors: Rich, Benjamin J., Montoya, Chris, Jin, William H., Spieler, Benjamin O., Mahal, Brandon A., Delgadillo, Rodrigo, Bilusic, Marijo, Abramowitz, Matthew C., Pollack, Alan, Dal Pra, Alan
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.11.2022
• Subjects: prostate cancer; salvage; oligometastases; oligorecurrent; radiation therapy
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2022.05.040

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.