MRI-based low dose-rate brachytherapy experience in locally advanced cervical cancer patients initially treated by concomitant chemoradiotherapy

Purpose: To retrospectively assess the physics contributions and the clinical outcome with preliminary 3D MRI-guided low dose-rate (LDR) intracavitary brachytherapy (BT) experience in locally advanced cervical cancer patients. Patients and methods: Eighty-four patients with primary locally advanced cervical carcinoma were analyzed. The median tumoral cervical volume was 48.0 cc (range 1-468 cc). Twenty-four patients (53%) had histological and/or radiological pelvic involvement. After pelvic ± paraaortic concomitant chemoradiation, a LDR BT boost was delivered to a 3D MRI-based clinical target volume taking into account dose volume constraints for critical organs and optimization of target volume coverage. Results: With a median follow-up of 53 months (range 31-79 months), the 4-year overall survival and disease-free survival rates were 57 (95%CI, 43-69) and 52% (95%CI, 40-64), respectively. Adding EBRT and LDR using EQD2 model, the median D₁₀₀ and D ₉₀ for the IR-CTV were 56.5 Gy_{α/ β10} (range 37-83 Gy_{α /β10}) and 69 Gy_{α /β10} (range 52-113 Gy _α/β10), respectively. For HR-CTV, the median D₁₀₀ and D₉₀ were 67 Gy _α/β10 (range 47-119 Gy_α/β10) and 79 Gy _α/β10 (range 53-122 Gy_α/β10), respectively. Thirty-nine late complications were observed in 28 patients (33.3%): 13 bladder, 7 rectal, 5 small bowel, 4 urethral, 3 colic, 2 vaginal, 1 pelvic fibrosis, and 4 others. Four grade 3 delayed complications were observed and no grade 4 complication occurred. Conclusions: Applying an individual treatment planning with 3D MRI-guided LDR brachytherapy appears to be feasible and efficient for patients with locally advanced cervical cancer in routine clinical practice.