Dr. Ost noted that lymph node recurrences are in the N1 location in 50% of cases and M1a 33% of the time. There are several radiotherapy approaches available for these patients, including (i) stereotactic body radiotherapy, which targets the node specifically with one to five fractions of treatment, and (ii) elective nodal radiotherapy, which targets a region that is suspicious on imaging with 25-28 fractions of treatment.
The potential added value of whole pelvis radiotherapy compared to standard extended salvaged lymph node treatment is that the percentage of N1 lesions in the treatment template is 80% for whole pelvis radiotherapy compared to 55% for standard therapy. Additionally, for M1a lesions, 68% are in the template region for whole pelvis radiotherapy, compared to 0% for standard treatment.
In a study comparing the outcome and toxicity of stereotactic body radiotherapy (n=309) and elective nodal radiotherapy (n=197), De Bleser and colleagues1 compared outcomes among these 506 patients. Elective nodal radiotherapy was associated with fewer nodal recurrences compared with stereotactic body radiotherapy (p < 0.001). In multivariable analysis, patients with one lymph node at recurrence had longer metastasis-free survival after elective nodal radiotherapy (hazard ratio [HR] 0.50, 95% confidence interval [CI] 0.30-0.85) compared to stereotactic body radiotherapy. Furthermore, late toxicity was higher after elective nodal radiotherapy compared with that after stereotactic body radiotherapy (16% vs. 5%, p < 0.01). The pattern of recurrence for these patients is as follows:
In a study from Steuber et al.,2 among patients with a prostate-specific antigen (PSA) relapse following radical prostatectomy plus post-operative radiotherapy, multidisciplinary therapy (salvage lymph node dissection or stereotactic body radiotherapy for N1/M1a disease) versus standard of care (delayed or immediate androgen deprivation therapy [ADT]) was associated with a 3% cancer-specific survival gain at five years and a 10% cancer-specific survival gain at 10 years. This data suggests that multidisciplinary treatment for these patients leads to optimal outcomes.
Dr. Ost concluded his presentation noting that both stereotactic body radiotherapy and elective nodal radiotherapy have good outcomes and favorable toxicity profiles. Additionally, randomized trials in this disease space are currently underway.
Presented by: Piet Ost, MD, PhD, Adjunct Head of Clinic - Radiation oncology, Assistant Professor, Faculty of Medicine and Health Sciences, University of Ghent, Ghent, Belgium
Written by: Zachary Klaassen, MD, MSc, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, Augusta, Georgia, USA, Twitter: @zklaassen_md at the Virtual 2020 EAU Annual Meeting #EAU20, July 17-19, 2020.
References:
- De Bleser, Elise, Barbara Alicja Jereczek-Fossa, David Pasquier, Thomas Zilli, Nicholas Van As, Shankar Siva, Andrei Fodor et al. "Metastasis-directed therapy in treating nodal oligorecurrent prostate cancer: a multi-institutional analysis comparing the outcome and toxicity of stereotactic body radiotherapy and elective nodal radiotherapy." European Urology 76, no. 6 (2019): 732-739.
- Steuber, T., C. Jilg, P. Tennstedt, A. De Bruycker, D. Tilki, K. Decaestecker, T. Zilli et al. "Standard of care versus metastases-directed therapy for PET-detected nodal oligorecurrent prostate cancer following multimodality treatment: a multi-institutional case-control study." European Urology Focus 5, no. 6 (2019): 1007-1013.