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Differences of Dose to Pelvic Organs at Risk (OAR) with Use of Vaginal Multi-Channel Cylinder Applicator for Adjuvant High-Dose Rate (HDR) Brachytherapy to the Vaginal Cuff

T Neicu*, V Valakh, P Chan, P Charpentier, S Li, Temple University Hospital, Phila., PA

SU-E-T-342 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: We reviewed the use of Vaginal multi-channel cylinder applicator (VCMC) in adjuvant HDR brachytherapy with the goal of reducing dose to OAR while completely covering the entire proximal vaginal cuff.
Methods: Two patients underwent total hysterectomy for endometrial carcinoma and received combined 5 fractions of Ir-192 HDR brachytherapy to the vaginal cuff as a portion of their postoperative regimens. Treatment was delivered using a commercially available Nucletron CT/MR compatible VCMC. The dwell time distribution for multiple lumens was optimized to maintain at least 95% of CTV within 95% of isodose line (V95 > 95%) while keeping dose to all OAR as low as possible. For comparison, plans were created using the central channel only simulating single-channel (SC) cylinder treatments. Related samples Wilcoxon signed rank test was used to test for statistical significance.
Results: Average CTV V200 was 39.7 ± 1.5 % of prescribed dose for VCMC plans vs. 32.5 ± 0.5 % for SC (p=0.04). Average CTV V150, V95, and V90 were 58.4 ± 2.0 %, 98.1 ± 1.0 %, and 99.4 ± 0.5 % for VCMC and 51.1 ± 0.3 % (p=0.04), 96.5 ± 0.6 % (p=0.04) and 98.8 ± 0.4 % (p=0.08) for SC. Average maximum point vaginal surface dose as a percentage of prescribed dose was similar: 294.5 ± 62.4 % for VCMC and 295.9 ± 79.7 % for SC. We also calculated the average D0.1cc, D1cc, D2cc and D10cc for bladder, rectum, sigmoid, and small bowel.
Conclusion: Use of VCMC reduced D0.1cc, D1cc and D2cc for the rectum; however bladder D0.1cc and D10cc were lower for SC. While CTV V200 and V150 were higher for VCMC, maximum dose to vaginal surface was similar. Additional dosimetric and clinical studies of VCMC use are necessary.

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