GPP06 Presentation Time: 9:45 AM

Abstract

Purpose

Consensus recommendations for CT based contouring in Image Guided Adaptive Brachytherapy (CT-IGABT) for cervical cancer were published by IBS-GEC ESTRO-ABS. However, real world outcome data of patients treated based on these recommendations is sparse. The purpose of this study is to present early outcomes of cervical cancer patients treated with CT-IGABT using the IBS-GEC ESTRO-ABS recommendations.

Material and Methods

Retro-LACER is a mono-institutional database of cervical cancer patients treated with CT-IGABT using uniform target delineation protocols between August 2020 and July 2023. All consecutive patients with biopsy proven locally advanced cervical cancer (FIGO Stage IB3 to IVA) who received curative (chemo) radiation at our institution were screened. While the dosimetric details were maintained prospectively, outcome and treatment related morbidity data is collected retrospectively from the electronic medical records.

Results

Out of 318 patients screened, 73 were excluded as per the eligibility criteria (2, stage ≤ IB2; 3 stage IVB; 19, received EBRT elsewhere; 17 defaulted / received BT elsewhere; 21, participants in other interventional studies; 11, did not come for at least one post treatment follow up). Disease and treatment characteristics of the 245 patients included in this analysis are presented in Table 1. Hybrid IC+IS BT was used in 51.4% of patients. About 64.5% of patients were treated in a basic CT environment (CT alone at BT), while 35.5% were treated in an advanced CT environment (pre-BT MRI, in 3.6% and Trans-Rectal ultrasonography in 31.8%). Median volume of CTV_HR was 31cc, while median D90 and D98 to CTV_HR (in EQD2_10Gy) were 88 and 79, respectively. Median D2cc for bladder, rectum and sigmoid (in EQD2_3Gy) were 89, 68 and 67, respectively. Dosimetric details of patients treated in basic and advanced CT environments are also presented in Table 1. At a median follow up of 17 months (IQR, 9 to 26), 12 patients (4.9%) died due to disease and 3 (1.2%) were lost to follow up. Treatment failure was observed in 27 patients (11%), with isolated local, regional (pelvic), regional (para-aortic), regional (pelvic + para-aortic) and distant failures in 3 (1.2%), 0 (0%), 5 (2%), 1 (0.4 %) and 12 (5.2%) respectively. Combination of [local + regional], [regional + distant] and [local + regional + distant] failures was observed in 2 (0.8%), 3 (1.2%) and 1 (0.4%) respectively. Estimated survival probability (Kaplan-Meier) at 6 months and 1 year were 99.5% and 93% for local control, 99.1% and 92% for loco-regional relapse free survival and 100% and 95% for overall survival, respectively. Severe late GI and GU morbidity (CTCAEv5 ≥ Grade 3) was observed in 18 (7.3%) and 1 (0.4%), respectively. Among the patients who developed severe late GU and GI morbidity, median D2cc doses to bladder, rectum and sigmoid (in EQD2_3Gy) were 88, 71 and 68 respectively.

Conclusion

Early clinical outcomes of CT based IGABT treated using IBS-GEC ESTRO-ABS recommendations appear to be encouraging and acceptable. Further follow up of this cohort is warranted to understand the long-term outcomes.