ESTRO 2024 - Abstract Book

S237

Brachytherapy - Gynaecology

ESTRO 2024

Background : CT image based adaptive intracavitary brachytherapy (CTimICBT) for cervical cancer is gradually gaining acceptance and replacing the gold standard MRI image based ICBT due to its readily availability, quick, relatively inexpensive and familiarity by the radiation oncologist.

Aim and Objectives: To evaluate the outcomes and toxicities in locally advanced cervical cancer patients who underwent CT image based adaptive intracavitary brachytherapy after radical radiotherapy.

Material/Methods:

Between January 2016 & February 2021, 90 patients with locally advanced cervical cancer (FIGO IB3-IVA), treated with radical external radiotherapy (EBRT) + concurrent chemotherapy followed by CTimICBT were selected from database for the retrospective study. All patients had MRI pelvis done at completion of external bean radiation therapy prior to brachytherapy which was used to assess residual disease and to delineate high risk clinical target volume (HRCTV) at brachytherapy. ICBT planning and dose reporting to target (HRCTV) and organ at risks (bladder, rectum) followed the GEC-ESTRO recommendations. Clinical outcomes - local disease-free survival (LDFS) and overall survival (OS) by Kaplan –Meier method and treatment-related bowel, rectal and bladder toxicities were evaluated by CTCAE criteria. Univariable and multivariable analyses was done to determine prognosticators for survival end points

Results:

The median age was 50 years. 91% had squamous histology with 2/3rd having bulky (>4cm) disease. 94% had FIGO stages II and III. About a third had both pelvic & paraaortic lymph nodes. Patients received median EBRT dose of 50.4Gy in 28 fractions with concurrent platin based chemotherapy (91%) followed by image based ICBT of 7Gy/fraction for 3 fractions once / twice weekly. 74% achieved complete response at end of EBRT. The median overall treatment time (OTT = EBRT+ICRT) was 8 weeks. Median EQD2GyD90 dose to HRCTV was 84Gy. The median EQD2Gy 2cc rectal and bladder dose was 67Gy and 76Gy respectively. At median follow-up of 36 months, 3-year LDFS and OS for FIGO stage I, II, III were 100, 72, 66 and 100, 68, 65 respectively. Grade III acute bowel and rectal toxicity was seen in 3%. Late rectal and bladder toxicities were primarily grade I (7%). Factors significant on univariate analysis for outcomes were histology, OTT, response at end of EBRT and HRCTVD90. On multivariate analysis, OTT of ≤ 8 weeks, response at end of EBRT and HRCTVD90 >87Gy were favourable determinants for survival end points.

Conclusion:

CT image based adaptive intracavitary brachytherapy resulted in improvement in local control and OS with decreased toxicities. The response at end of EBRT, HRCTVD90 >87Gy and OTT <8weeks are prognosticators for outcomes.

Keywords: Single MRI followed by CT based adaptive ICBT

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Poster Discussion

MRI-based planning in transperineal interstitial brachytherapy for vaginal-involving tumours