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Dosimetric Comparison Between Syed-Neblett Interstitial and Multi-Channel Vaginal Cylinder HDR Brachytherapy in Locally Advanced Cervical Cancer

H Ai

H Ai*, X Lu , C Desrosiers , Indiana University School of Medicine, Indianapolis, IN


SU-I-GPD-T-57 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The purpose of this study is to evaluate the eligibility of substituting Syed-Neblett interstitial template for multi-channel vaginal cylinder (MCVA) in advanced cervical cancer brachytherapy by performing dosimetric comparison between two implant techniques.

Methods: 11 Syed-Neblett interstitial treatment plans from 7 patients with locally advanced cervical cancer (all lesions were less than 2 cm laterally spread from vaginal wall) were retrospectively reviewed. All patients were treated with EBRT to the whole pelvis at 45 Gy followed by brachytherapy using Syed-Neblett interstitial template with 25 mm diameter obturator. For dosimetric comparison, MCVA brachytherapy plans were generated based on the same CT scan and structure set by substituting Syed-Neblett template obturator for a MCVA with same diameter. Graphic optimization was used for shaping the isodose curve. D90 and D95 were matched with Syed-Neblett interstitial plan and OAR doses were minimized. Dosimetric parameters including D90, D95, V150 and V200 of HRCTV, D1cc and D2cc of bladder, rectum and sigmoid were compared using student t-test between Syed-Neblett and MCVA plans. EQD2 of HRCTV and OARs for each patient were calculated.

Results: MCVA plans have similar D90 and D95 with Syed-Neblett plans but higher mean values of V150, V200 and all doses of OARs. Among those dosimetric parameters, MCVA plans have significantly higher V150, V200, D1cc and D2cc of bladder and rectum. For MCVA plans, 2 out of 7 patients have bladder and rectum EQD2 higher than ABS recommended limits, 90 Gy and 75 Gy, respectively. Only one patient has sigmoid EQD2 higher than limitn. 3 out of 7 patients have all EQD2 within recommended limits.

Conclusion: For locally advanced cervical cancer, Syed-Neblett interstitial brachytherapy has superior dosimetric distribution than intracavitary brachytherapy but requires operating room with anesthesia and inpatient care. MCVA can be used to treat some patients with locally advanced cervical cancer.

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