Intensity Modulated Radiotherapy is a Well-Tolerated and Effective Treatment for the Long-Term Control of Intra-Abdominal and Retroperitoneal Oligometastatic Renal Cell Cancer

Background: The use of conventionally fractionated intensity modulated radiotherapy (IMRT) in the management of oligometastatic renal cell carcinoma (RCC) is currently poorly characterised in the literature. Objective: To evaluate the safety and effectiveness of IMRT for intraabdominal and retroperitoneal RCC oligometastases. Methods: Retrospective analysis of 14 patients with oligometastatic RCC treated with IMRT with the aim of inducing long-term control. Indications for radiotherapy included bleeding abdominal mass (5 patients), solitary renal bed recurrence (5 patients) and isolated, asymptomatic pancreatic mass (4 patients). The prescribed radiotherapy dose was 50 Gray in 20 to 25 fractions. Patients were followed up long-term using regular cross-sectional imaging and clinical review to assess local and distant disease control and treatment related toxicity. Results: At median follow up of 33.5 (6–68) months, 12 patients remain alive (86%), of whom 11 (92%) have no evidence of local recurrence. Six patients (43%) developed further metastatic disease, of whom 4 (67%) received systemic treatment. Median duration of local control was 33.5 months, and 1- and 3-year overall survival (OS) was 92.9% and 85.7% respectively. No treatment-related toxicities ≥ grade 3 and no long-term sequelae were observed. Conclusions: IMRT to intra-abdominal and retroperitoneal metastasis in oligo-metastatic RCC can be delivered safely, provide durable responses and excellent longer-term survival if given to a sufficiently high dose over a conventionally fractionated course. Our study is the first to date with long-term follow up to evaluate the role of IMRT in such cases and has important implications for treatment of oligometastatic RCC.