Radiosurgery for Patients with Oligometastasis to Retroperitoneal Lymph Nodes

Purpose: We report both the control and the toxicity of Stereotactic Body Radiotherapy (SBRT) therapy in a series of oligometastatic cancer patients with Retroperitoneal lymph Node (RPLN) involvement. Methods: This is a retrospective review of a prospective database. Eligible patients for review received SBRT to metastatic RPLN. 26 patients with RPLN failure (median age: 61, 3 males) were treated with SBRT. Treatment was to an isodose line (median: 65%). Median dose was 27.5 Gy (range: 15-54 Gy) and median fractions were 5 (range: 3-5). Results: 26 patients were analyzed with a median follow-up of 13 months and 22 months for surviving patients. 16 patients (61.5%) had distant cancer recurrence after SBRT, while 5 patients (19.2%) had a local recurrence at the site of SBRT. Six patients (23%) had grade 2 toxicities, including nausea/vomiting, constipation, and abdominal pain. There were no grade 3 or higher toxicities and no late toxicities. Overall survival was improved in patients with distant control (median survival for patients with distant failure was 430 days versus 845 days for patients without distant relapse, P < 0.047). Higher Biological Equivalent Dose (BED) predicted for improved local control (P < 0.027), we did not find any local failures with a BED-10 greater than 50 Gy. Conclusion: SBRT in the treatment of RPLN recurrences is safe and effective. We recommend treatment to a dose greater than BED-10 50 Gy, our preferred dose regimen is 35 Gy in 5 fractions. Improved distant control was associated with an improved OS in this series.