Outcomes and comparison of dosimetric parameters between intracavitary (Fletcher) and combined intracavitary/interstitial (Utrecht) brachytherapy in locally advanced cervical cancer.

Objective: To report outcomes of combined intracavitary/interstitial (IC/IS) image-guided brachytherapy (IGBT) in locally advanced cervical cancer, and to compare its dosimetric parameters with intracavitary-only (IC) brachytherapy in a first-in-country experience.

Methods And Materials: Between January 2021 and September 2022, a total of 160 insertions were done in 40 patients with FIGO IB3-IVA cervical cancer undergoing IGBT using a hybrid (Utrecht) applicator. Corresponding treatment plans for IC brachytherapy were generated during treatment, and optimized. A preplanned comparison of dosimetric parameters, defined in GEC-ESTRO was conducted.

Results: The clinical use of a hybrid IC/IS applicator was feasible in all insertions. An average of 14 needles were inserted in each patient over four fractions. Mean HR-CTV D90 and D98 was 86 (SD 1.9) Gy and 75.7 (SD 2.3) Gy using hybrid applicator, and 80 (SD 5.4) Gy and 69.8 (SD 5.2) Gy using IC applicator, with a mean dose gain of 6.0 (SD 5.0) Gy and 5.9 (SD 4.7) Gy (p <0.001), respectively. Likewise, mean D2cc for bladder and sigmoid were significantly lower in the hybrid technique. Mean contribution of brachytherapy to total HR-CTV D90 (in absolute EQD2 Gy) was 41.7 Gy using IC/IS applicator while 35.7 Gy for IC-only applicator (p = 0.027). Clinical response at 12 weeks showed an overall response rate (ORR) and complete response (CR) rates of 92.5% and 77.5%, respectively.

Conclusions: IGBT using a hybrid IC/IS applicator showed excellent tolerability and yielded favorable results, resulting in significant dosimetric improvement in terms of primary target dose, and sparing OARs.