Defining Optimal Nodal Dose for Stage IIIC Cervical Cancer: An Institutional Audit of Patients Treated with Simultaneous Integrated Nodal Boost

Abstract Objective To assess radiation dose-response relationship for individual lymph nodes in patients with stage IIIC cervical cancer who are treated with simultaneous integrated boost (SIB). Methods This is a retrospective study in which patients with stage IIIC cervical cancer treated with (chemo)radiation who received simultaneous integrated nodal boost (SIB) and brachytherapy were evaluated with the primary aim of determining in-field nodal control. Secondary aims included estimation of local control (LC), disease free survival (DFS) and adverse events. Univariate analysis and multivariate analysis was performed for factors impacting nodal control, LC and DFS. Results One hundred and fifty-one (151) nodes in 65 patients were included. The median number of lymph nodes and nodal volume was 2 (1–6) and 3.4 cc (1.8–6.8 cc) respectively. Median SIB dose was 55Gy/25# (53.7–55.0 Gy). At a median follow-up of 43 months the in-field nodal control was 99.3% (1/151). The 5-year LC, DFS and regional nodal control was 88.7, 66 and 85.6% respectively. The 5-year DFS for FIGO stage IIIC1 was 67.7% versus 43.5% for stage IIIC2 ( p = 0.03) and lymph node volume >3cc was associated with reduced 5-year DFS (80.8% vs. 55%, p = 0.03) on univariate analysis. No factor was statistically significant on multivariate analysis. A vast majority of lymph node recurrences were observed in elective nodal regions outside the true pelvis that received lower contribution from brachytherapy. Conclusion Nodal SIB doses of up to 55Gy/25#/ 5 weeks administered during chemoradiation are associated with 99.3% 5-year infield nodal control. A vast majority of nodal recurrences were observed in elective volumes that received a lower contribution from brachytherapy.