Oncologic outcomes after MRI-assisted image-guided brachytherapy with hybrid interstitial and intra-cavitary applicators under moderate sedation for locally advanced cervix cancer

Purpose: To report outcomes of using image-guided hybrid intra-cavitary/interstitial applicators under moderate sedation for locally advanced cervical cancer patients in our institution.

Material and methods: A total of 69 fractions of brachytherapy with hybrid applicators were performed in 33 patients from January 2017 to April 2021. All patients underwent MRI pelvis 1 week pre-brachytherapy to determine suitability for interstitial brachytherapy and pre-plan needle placement. All insertion of applicators were performed under moderate sedation with midazolam and/or fentanyl. Fifty-eight (84.1%) fractions were planned with CT alone. Clinical outcomes, dose volume parameters, and toxicities were analyzed.

Results: The median follow-up was 28 months. A total of 320 needles (median, 5 needles per fraction) were implanted, with a median insertion depth of 3 cm (range, 1.5-4 cm). The median high-risk clinical target volume (HR-CTV) during initial brachytherapy was 34.5 cc (range, 17.8-74.7 cc). The median total EQD₂ D_2cc of the rectum, bladder, sigmoid, and small intestine colon was 71.8 Gy, 81.5 Gy, 69 Gy, and 58.3 Gy, respectively. The 2-year local control and overall survival were 80.7% and 77.7%, respectively. Larger volume HR-CTV was significantly associated with worse local control (HR = 1.08, p = 0.005) and overall survival (HR = 1.04, p = 0.015). None of the patients required in-patient admission or blood transfusion post-procedure. Late grade 3 gastrointestinal and genitourinary toxicities were observed in 4 patients (12.2%).

Conclusions: Hybrid applicators inserted under moderate sedation are feasible and safe. Image-guided interstitial brachytherapy with CT planning aided by MRI performed 1 week pre-brachytherapy is associated with favorable outcomes and modest toxicities.