GPP11 Presentation Time: 10:20 AM: Simple Needle Attachment Post Placement Interstitial Template (SNAPP-IT) Enabling a Shorter, More Direct Needle Path While Preserving Tumor Visualization

Abstract

<h3>Purpose</h3> Classical interstitial brachytherapy attaches the interstitial template to the perineum and then has needles traverse a long distance of normal tissue to reach the tumor. In clinical practice, tumors requiring interstitial brachytherapy are frequently relatively easily visualized with vaginal speculum exam, but classical interstitial templates hinder this direct visualization when sutured in place and require users to insert needles far from the target tumor. Having an interstitial template that allows needles to be inserted closer to the tumor while maintaining direct visualization of the tumor and shortening the needle path would be advantageous. <h3>Materials and Methods</h3> We developed a novel interstitial template that allows needles to be inserted into the region of the tumor with direct visualization (Figure 1A) and subsequent attachment and fixation to the template (Figure 1B). The template contains 42 secure press-fit "snap" anchoring locations for commercially available 2 mm plastic Varian needles. Following placement of the needles within the region of the tumor, the template can be sutured to the perineum, then the needles can be snapped into the press-fit locations and then further secured with the additional securing cover (Figure 1C). Additionally, the template can accommodate and secure a 2.5 cm vaginal cylinder (Figure 1D). We started using this new interstitial template in clinical practice in March 2021 and compared procedure time, needle path lengths, and plan dosimetry from the new template and traditional cases. Twenty SNAPP-IT cases were performed in our department over the past year and were compared to 20 traditional interstitial cases (Varian Kelowna or BEBIG M.A.C. templates) performed March 2019-October 2020. <h3>Results</h3> In clinical use the novel SNAPP-IT had an average procedure time of 85 minutes, approximately 17% shorter than the average of 102 minutes for the 20 traditional template cases. The average CTV volume was 25.6 cc for SNAPP-IT, 20.7 cc for traditional. The SNAPP-IT and traditional cases averaged similar number of needles (15.8, 15.6) with similar dosimetry an average V100% of 95.1%, 93%, respectively. The traditional template-based needle insertion depth (average length from skin to the superior extent of the tumor) averaged 11.8 cm whereas the direct SNAPP-IT approach averaged 3.8 cm (average length from vaginal mucosa to the superior extent of the tumor), a decrease of 2/3 in the required needle insertion depth. <h3>Conclusions</h3> Our team developed a novel interstitial template for gynecologic brachytherapy that maintains direct visualization of the tumor while offering a substantially shorter and more direct needle insertion path and allows simple needle attachment post placement. The simple snapping of the needles into the template allows a quick and secure fixation. Our initial clinical experience shows increased ease of performing needle insertion with SNAPP-IT compared to traditional cases with decreased average procedure time, shorter needle paths from insertion through the extent of the tumor, and at least equivalent dosimetry.