Simultaneous Integrated Boost for Dose Escalation in Node-Positive Cervical Cancer: 5-Year Experience in a Single Institution

SIMPLE SUMMARY: Nodal control is a major challenge for locally advanced cervical cancer (LACC) treated with definitive chemoradiotherapy. The optimal radiotherapy regime for patients with node-positive disease is yet to be defined. Modern image-guided intensity-modulated radiotherapy offers the potential for dose escalation to involved nodes while minimizing doses to organs at risk. This study reports the efficacy and toxicity of a simultaneous integrated boost in an Asian cohort with node-positive LACC in the context of contemporary volumetric modulated arc therapy and magnetic resonance image-guided adaptive brachytherapy. A total of 234 involved nodes in 54 patients were analyzed. Excellent nodal control was achieved, with four (2%) boost-volume failures occurring in three patients. The 2-year actuarial regional nodal control (RNC), pelvic control (PC), locoregional control (LRC), disease free survival (DFS), and overall survival (OS) were 93%, 87%, 87%, 78%, and 85%, respectively. The incidence of grade ≥ 3 radiotherapy-related toxicity was low. The 5-year local experience demonstrated excellent treatment outcomes with an acceptable toxicity profile. ABSTRACT: This study retrospectively evaluates clinical outcomes of dose escalation to involved nodes using volumetric modulated arc therapy (VMAT) with simultaneous integrated boost (SIB) for node-positive locally advanced cervical cancer (LACC) at a single institution. Consecutive patients with node-positive LACC (FIGO(2018) IIIC1-IVA) who received definitive chemoradiotherapy by VMAT 45 Gy in 25 fractions with SIB to 55–57.5 Gy, followed by magnetic resonance image-guided adaptive brachytherapy (IGABT) between 2018 and 2022 were identified. A standardized strategy regarding nodal boost delivery and elective para-aortic (PAO) irradiation was employed. Primary endpoints were involved nodal control (INC) and regional nodal control (RNC). Secondary endpoints were pelvic control (PC), locoregional control (LRC), disease-free survival (DFS), overall survival (OS), failure pattern, and radiotherapy-related toxicities. A total of 234 involved nodes (182 pelvic and 52 PAO) in 54 patients, with a median of 3 involved nodes per patient (range 1–16), were analyzed. After a median follow-up of 19.6 months, excellent INC was achieved, with four (2%) boost-volume failures occurring in three patients. The 2-year actuarial RNC, PC, LRC, DFS, and OS were 93%, 87%, 87%, 78%, and 85%, respectively. Adenocarcinoma histology was associated with worse RNC (p = 0.02) and OS (p = 0.04), whereas the primary tumor maximum standardized uptake value (SUVmax) was associated with worse PC (p = 0.04) and LRC (p = 0.046) on univariate analysis. The incidence of grade ≥3 acute and late radiotherapy-related toxicity were 2% and 4%, respectively. Treatment of node-positive LACC with VMAT with SIB allows safe and effective dose escalation. The 5-year local experience demonstrated excellent treatment outcomes without additional toxicity.