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Objective: To investigate the clinical outcomes and toxicity in patients with locally advanced cervical cancer treated with supplementary applicator guided-intensity modulated radiation therapy (IMRT) based on conventional intracavitary brachytherapy (IC/IMRT). Design: A retrospective cohort study. Setting: Sichuan Cancer Hospital & Institute, Sichuan Cancer Centre, China. Population: Large high-risk clinical target volume (HR-CTV) volume (>40 ml) at the time of brachytherapy cervical cancer patients were recruited. Methods: This study is a retrospective analysis of 76 patients with locally advanced cervical cancer (FIGO IIB-IVA) treated with concurrent chemoradiotherapy followed by IC/IMRT between June 2010 and October 2016. External radiotherapy (45 Gy in 25 fractions) was adminstered with cisplatin chemotherapy treatment before IC/IMRT. The IMRT plan was optimised using the ICBT plan base dose plan by an inverse dose optimisation tool which allows the use of DVH constraints on the total dose of ICBT. A seven-field gantry angle IMRT plan was devised to avoid hotspots when optimising the boost plan. The prescription dose for HR-CTV and IR-CTV were 6 and 5 Gy per fraction for five fractions, respectively. Results: Mean HR-CTV was 65.8 ± 23.6 ml at the time of brachytherapy. D90 for HR-CTV and IR-CTV were 88.7 ± 3.6 Gy and 78.1 ± 2.5 Gy. D2cc for bladder, rectum, sigmoid and small intestine were 71.8 ± 3.8, 64.6 ± 4.9, 63.9 ± 5.3 and 56.7 ± 8.7 Gy, respectively. Median follow-up was 85 months (47.9–124.2 months). Five-year local recurrence-free survival rate, metastasis recurrence-free survival rate, disease-free survival rate and cancer-special survival rate were 87.6, 82.4, 70.9 and 76.3%, respectively. The grade 1 + 2 gastrointestinal and urinary late toxicities were 15.8 and 21.1%, and grade 3 late toxicities were 3.9 and 5.2%, respectively. Neither acute nor late grade 4 gastrointestinal or urinary toxicities were seen. Conclusions: The combination of ICBT with an applicator-guided supplementary IMRT boost achieved excellent local control and overall survival with low toxicity for bulky residual cervical tumour. [ABSTRACT FROM AUTHOR]