ESTRO 2024 - Abstract Book

S278

Brachytherapy - Gynaecology

ESTRO 2024

emilie natier 1 , benoît alignet 2 , camille roukoz 2 , salvatore cozzi 2 , frederic lafay 3 , magali sandt 3 , frederic gassa 3 , anne agathe serre 2 1 Centre hospitalier universitaire, Department of Radiation Therapy, saint etienne, France. 2 centre léon bérard, Department of Radiation Therapy, lyon, France. 3 centre léon bérard, Medical physics unity, lyon, France

Purpose/Objective:

Interstitial brachytherapy (ISBT) following chemoradiotherapy (CRT) represents the standard of care of locally advanced cervical cancer (LACC). In case of bulky tumor the choice of the more adapted applicator and brachytherapy (BT) implant ensuring a sufficient coverage of residual gross tumor volume (GTV) to improve local control (LC) remain a challenge. ISBT has been developed to allow a better dose distribution of asymmetrical volume topography. Nevertheless, some applicators remain inadequate for large tumoral extension like infiltrative vaginal diseases. In this study, we focused on the treatment of patient with cervical cancer and lower third vaginal third involvement (LTI).

Material/Methods:

This retrospective cohort included from January 2011 to December 2021, patients with histology confirmed LACC with LTI treated with CRT and BT, from January 2011 to December 2021 . All patients underwent, clinical examination and magnetic resonance imaging (MRI) were performed before both CRT and before BT to assess local extension, and particularly the length and thickness of the vaginal involvement : lenght and thickness. Two different techniques of BT were available : (1) a hybrid application combining the « Utrecht » applicator and with freehand vaginal interstitial needles and (2) an integrated system the « Venezia » applicator offering multichannel vaginal caps and possibilities of transperineal implants using a perineal template. We evaluated clinical outcomes and dosimetryic datas.

Results:

Thirty-one LACC patients with LTI were included, 32.,3% were classified as FIGO stage IIIA, 6.,5% FIGO IIIB, 29% FIGO IIIC1, 3.,2% FIGO IIIC2 and 29% FIGO IVA. After CRT, 7 patients (22.,5%) had a complete response and 15 patients (48.,4%) had a vaginal persistant disease. Tthe mean invaded vaginal thickness was 15.,3mm (7-33mm) at diagnosis, and after CRT, 3.,7mm (2-18mm) after CRT. Sixteen patients were treated with the « Utrecht » applicator and 15 with the « Venezia » applicator. To treat the vaginal disease, the vaginal caps were used for 12 patients, vaginal interstitial needles for 8 patients and intracavitary vectors were sufficient for 11 patients. Comparing the 2 subgroups of patients treated with interstitial needles or vaginal caps, the mean thickness of post-CRT and pre-BT vaginal infiltration was lower in the vaginal caps group (2.25mm vs 7mm). According to the GEC-ESTRO recommendations, all techniques achieved a good coverage of target volumes and dose constraints to bladder, sigmoid and bowelthe organs at risk were respected. The CTV coverage by BT was similar in the two sub-groups. Only the median D2cc to the rectum was significantly lower in the vaginal caps group, including both External Beam Radiation Therapy and BT (59.5Gy vs 66.4Gy, p=0.026). Median follow-up was 26.,2 months (4.,5 66.,7 months). Most patients presented metastatic disease (n=11, 35.5%), while Four 4 patients (12.,9%) recurred only locally, one 1 (3.,2%) had local and regional recurrence, and 4 (12.,9%) only regional recurrence and 11 (35,5%) a metastatic disease. At 2 years, lLocal recurrence-free survival, loco-regional recurrence-free survival, disease free survival and overall survival were estimated at 2 years, respectively at 68% (95%CI: 51.,6-89.,6%), 65.,7% (95%CI: 49.,6-87.,1%), 48.,3% (95%CI: 27.,5-61.,6%), 76.,2% (95%CI: 61-95.,1%) respectively. Comparing the two 2 sub-groups of patients treated with interstitial needles or with the vaginal caps, the mean thickness of post-CRT and pre-BT vaginal infiltration post-CRT and pre-BT was lower in the vaginal caps group (2.,25mm vs 7mm). The CTV coverage by BT was similar in the two sub-groups. Only the median D2cc to the rectum was significantly lower in the vaginal caps group, including External Beam Radiation Therapy and BT (59.,5Gy vs 66.,4Gy, p=0.,026).