PO35 Presentation Time: 10:30 AM

Purpose

The Venezia gynecological applicator (Elekta) is a hybrid interstitial/intracavitary brachytherapy applicator used to treat cervical cancers. Previous data supporting the use of hybrid brachytherapy comes mainly from the EMBRACE cohort showing increased coverage of the high-risk CTV (HR-CTV) with decreased toxicity. Single-institution data, further supports this technique. We undertook this study to report our initial experience with the Venezia applicator for treatment of locally advanced cervical and endometrial cancers.

Materials/Methods

We retrospectively reviewed 21 patients who received brachytherapy using the Venezia applicator for definitive treatment of cervical or endometrial cancer, treated from June, 2021 to March, 2022. All patients completed chemoradiotherapy followed by brachytherapy boost. For each brachytherapy fraction, patients received sedation and the Venezia applicator was placed. Radiation treatment planning was performed on CT imaging fused to daily MRI, using the Oncentra® treatment planning system. If needles were required for hybrid interstitial brachytherapy, the plan was optimized first without utilizing the needles, to meet constraint to organs at risk (OARs). Subsequently, planning was performed considering the interstitial needles with a focus on optimizing the balance of target coverage and dose to organs at risk. Radiation dose to target volumes and organs at risk were recorded as equivalent dose in 2Gy fractions (EQD2).

Results

Median age was 54 years. Ninety percent of patients were treated for a primary cervical cancer and 10% for primary endometrial cancer. Twenty-nine percent of patients had T1 primary tumor, 48% had a primary T2 tumor and 24% had a primary T3 tumor. The most common histology was squamous cell carcinoma (SCC) in 76% of patients, with adenocarcinoma in 10% and the remaining being undifferentiated or endometrioid. Median follow up was 4.3 months. Thirty-three percent of patients experienced acute toxicity with brachytherapy, all of which were grade 1-2. Twenty-nine percent experienced acute GI toxicity, 10% experienced acute GU toxicity and 10% experienced bleeding. Median brachytherapy dose and fractionation was 28Gy delivered over 4 fractions. Sixty-two percent of patients required hybrid interstitial brachytherapy and the median number of interstitial needles placed was 4. Median volume of the Gross Tumor Volume (GTV) and HR-CTV at first fraction were respectively 5.22cm³(IQR 4.26cm³-10.28cm³) and 27.84cm³(IQR 24.71cm³-40.36cm³⁾. Median HR-CTV D90 and D98 were respectively 85.3Gy(IQR 83.1Gy-88.8Gy) and 76.8Gy (IQR 74.2Gy-79.6Gy). Median GTV D98 was 98.4Gy (IQR 94.3Gy-116.3Gy). Regarding OARs, median D2cc dose to the rectum, sigmoid and bladder were respectively 56.9Gy (IQR 53.7Gy-59.1Gy), 60Gy (IQR 55.9Gy-63.7Gy) and 75.3Gy (IQR 72.3Gy-77.6Gy). Median D1cc dose to the bowel was 50Gy (IQR 46.6Gy-56.8Gy). Median D0.1cc dose to the left and right ureter were respectively 71.8Gy (IQR 62.6Gy-85Gy) and 67.5Gy (IQR 61.6Gy-89.1Gy).

Conclusions

Brachytherapy using the Venezia hybrid applicator was implemented with good dosimetry and sparing of organs at risk. Procedure related complications were mild.