PP04  Presentation Time: 10:27 AM: A Randomized Cross-Over Study of a Hydrogel Packing System Compared to Standard Packing during Image-Guided High-Dose Rate Brachytherapy Boost for Cervical Cancer.

Brachytherapy (BT) boost with vaginal packing (VP) is standard of care for locally advanced cervical cancer. The goals of VP are to physically displace bladder and rectum (OARs) from the high dose radiation region and to stabilize the BT applicators. The BrachyGel Vaginal Hydrogel Packing System (BrachyGel) was developed as a new technique to improve the quality of VP for cervical cancer BT, including OAR dosimetry, patient comfort, ease of physician use, reproducibility, and visibility on MRI. The purpose of this study was to determine how the use of BrachyGel compares to standard gauze during high dose rate (HDR) BT for cervical cancer. This is a prospective randomized cross-over study. Patients with stage IB1 - IVB cervical cancer receiving definitive chemo-radiation with HDR BT boost (intracavitary +/- interstitial) were enrolled. All patients received gauze for their 1st fraction (Fx) and were subsequently randomized to BrachyGel for either the 3rd and 5th Fx (Arm A) or 2nd and 4th Fx (Arm B). Patient reported discomfort on a 4-point Likert scale was collected. Physicians and physicists evaluated imaging properties, completeness of packing, and ease of use. Adverse events (AEs) were prospectively collected and scored per CTCAE. MRI was not performed after VP insertion for this cohort, but was asynchronously obtained for BT planning. 20 evaluable patients were enrolled. The majority of patients had squamous cell histology (70%), and FIGO IIB (35%) or IIIC (35%) disease. For the primary endpoint of D2cc dosimetry comparison, the mean difference of Bladder D2cc (gauze - BrachyGel) in Fx 2 & 3 was 0.117 Gy ± 0.54 and 0.013 Gy ± 1.24 in Arms A and B, respectively, both in favor of BrachyGel. The mean difference of Rectum D2cc was -0.189 Gy ± 0.48 and -0.19 Gy ± 0.62 in Arms A and B, respectively, both in favor of gauze. The high risk clinical target volume (HR-CTV) D90 mean difference (gauze - BrachyGel) was -0.120 Gy ± 1.48 in Arm A and 0.601 Gy ± 1.48 in Arm B. There were no clinically relevant observed differences between gauze and BrachyGel between arms. Figure 1 displays the OAR dosimetry across 5 Fx for each arm and plots the variability of dosimetry. Patient reported discomfort with the VP experience was scored as none, mild, moderate, or severe for BrachyGel 23.3%, 36.7%, 33.3%, 6.7% as compared to 7.4%, 44.4%, 29.6%, 18.5% with gauze, respectively. The clarity of VP was similar between BrachyGel and gauze with 86.8% and 60.5% of BrachyGel cases scored as "very clear" or "clear" by physicists and physicians, respectively, compared to 89.7% and 66.7% in gauze cases. Completeness of VP was more frequently "excellent" or "good" with BrachyGel (79.0%) compared to gauze (56.4%). The ease of packing was considered "extremely easy" (21.2%) or "somewhat easy" (66.7%) more frequently with BrachyGel cases compared to gauze (0% and 72.4%, respectively). We observed no increase in AEs associated with BrachyGel. This prospective randomized cross-over study of BrachyGel VP for cervical cancer BT reports no difference between gauze and BrachyGel in OAR dosimetry or HR-CTV coverage. Imaging clarity on CT is similar between gauze and BrachyGel, but BrachyGel performs well compared to gauze for the patient and physician experience, including patient-reported discomfort, completeness, and ease of use. [ABSTRACT FROM AUTHOR]