The Role of Radiotherapy in the Treatment of Retroperitoneal Lymph Node Metastases from Colorectal Cancer.

Purpose: Retroperitoneal lymph node metastases are rare in colorectal cancer. Optimal treatment strategies are still unknown. Patients and Methods: We retrospectively enrolled colorectal cancer patients who had received radiotherapy for retroperitoneal lymph node metastases from 2009 to 2018. Patients with isolated retroperitoneal lymph node metastases or retroperitoneal lymph nodes with extra-retroperitoneal metastases were all included. A median dose of 60 Gy was delivered. Results: A total of 68 patients were enrolled in this study; 28 (41%) of them had extra-retroperitoneal metastases. In the isolated retroperitoneal lymph node metastases group, complete response was found in 5 patients (12.5%), partial response was achieved in 20 patients (50%), 9 patients (22.5%) had stable disease. The 1-, 2- and 3-year local control rates were 87.5%, 77.5%, and 70%. In the extra-retroperitoneal metastases group, the disease control rate was 75%, including complete response in 1 patient (3.6%), partial response in 4 patients (14.3%) and stable disease in 16 patients (57.1%). The 1-, 2- and 3-year local control rates were 57.1%, 42.8%, and 0%. The median overall survival was 59.4 months and 19 months in the isolated retroperitoneal lymph node metastases group and extra-retroperitoneal metastases group, respectively. In the isolated retroperitoneal lymph node metastases group, the 1-year and 3-year overall survival values were 90.2% and 75.8%, respectively. The 1-year and 3-year progression-free survival values were 57.9% and 0%, respectively. The extra-retroperitoneal metastases group experienced worse survival outcome (1-year overall survival: 57.9%, P<0.05; and 1-year progression-free survival: 22.5%, P<0.05). Conclusion: For patients with isolated retroperitoneal lymph node metastases, radiotherapy combined with systemic treatment can be used as a method to achieve no evidence of disease and can result in good local control and survival. For patients with extra-retroperitoneal metastases, although the survival is much worse than that of isolated retroperitoneal lymph node metastases, radiotherapy is an effective palliative treatment to relieve pain and obstruction based on systemic treatment.