Impact of Nodal Metastatic Volume on Distant Metastasis in Patients with Cervical Cancer and Para-aortic Nodal Metastases Treated With Definitive Radiation Therapy

Aims: To report institutional outcomes following definitive radiation therapy (RT) for cervical cancer with para-aortic lymph node (PAN) metastasis and explore the risk factors for subsequent distant metastasis (DM) and the optimal elective radiation field. Material and Methods: Ninety-seven patients treated between 2011 and 2023 were evaluated. The median patient age was 60 (range, 29–86) years. The numbers of patients with International Federation of Gynecology and Obstetrics (FIGO) 2008 stages I, II, III, and IVA were 6 (6%), 32 (33%), 43 (44%), and 16 (16%), respectively. Eighty-two patients had squamous cell carcinoma. The median gross tumor volumes of primary (GTVp) and nodal metastasis (GTVn) were 110.4 (range, 20.6–340.7) cm³ and 15.3 (range, 1.0–120.6) cm³, respectively. The median GTVn/GTVp ratio was 12.8%. The elective PAN field margin above the involved node was one vertebral height or less in 68% of the cohort. Extended-field RT was delivered using conventional three-dimensional conformal RT and intensity-modulated RT in 52 and 45 patients, respectively. The median radiation doses to the metastatic and elective regions were 56 and 50 Gy, respectively. Concurrent chemotherapy was administered to 90 (93%) patients. Results: With a median follow-up of 34 (range, 4–143) months, the 3-year in-field recurrence-free survival, DM-free survival, and overall survival rates were 74%, 51%, and 66%, respectively. Patients with a higher GTVn/GTVp ratio had a significantly higher risk of developing DM than their counterparts. Only two (2%) patients developed isolated PAN recurrence outside the irradiated field. Conclusions: DM is the most common mode of recurrence, the risk of which is significantly higher in patients with higher GTVn/GTVp ratios. An ample margin above the involved PAN may not necessarily be required to achieve disease control in the pelvis and PAN.