Objective To investigate the relationship between dose-volume histogram (DVH) parameters and the late side effects (LSE) of the rectum in external-beam radiotherapy combined with computed tomography (CT)-based brachytherapy for locally advanced cervical cancer.Methods From 2008 to 2011,18 patients with stage ⅡB-ⅢB cervical cancer received external-beam radiotherapy and CTbased brachytherapy.The DVH parameters of high-risk clinical target volume (HR CTV) D90,point A dose,and D1 cm3 and D2 cm3 of the rectum and bladder were calculated by Oncentra HDR treatment planning system.Survival outcomes were followed up and rectal LSE were evaluated by RTOG/EORTC grades.Results The point A dose and HR CTV D90 were (93.0 ± 5.5) Gy and (73.6 ± 11.9) Gy,respectively.The median follow-up was 26 months.No recurrence was found during follow-up.Eight patients had mild and moderate rectal LSE,and their rectum D2 cm3 and D1 cm3 were significantly higher than those of patients without mild and moderate rectal LSE (D2 cm3:(87.4 ± 3.8) Gy vs.(75.8 ± 7.4) Gy,P =0.004 ; D1 cm3:(96.4±6.6) Gy vs.(80.5± 7.1) Gy,P=0.001).Conclusions HR CTV D90 in CT-based brachytherapy for locally advanced cervical cancer might be lower than that in the MRI-based plan.Rectum D2 cm3 is recommended to be less than 75 Gy.

Objective To investigate the relationship between the channel design of tandem-andovoid (T&O) applicator and the doses to organs at risk (OARs) and target volume in three-dimensional brachytherapy for advanced cervical carcinoma.Methods The data on 15 patients with advanced cervical carcinoma treated with three-dimensional brachytherapy in our hospital from 2015 to 2016 were collected,and 30 randomly selected high-dose-rate titanium T&O plans were retrospectively studied.CT-guided,conformal brachytherapy plans were generated.To simulate T&O applicator,the tandem applicator was virtually compared with the T&O plans with the target volume and OARs remaining unchanged.The DVH parameters of the rectum,bladder,and sigmoid were compared using the paired t test.Results For T&O plans and tandem applicator plans,the mean D2cc of the rectum was 387.8±96.8 cGy and 340.8±88.1 cGy,respectively;the mean D2cc of the bladder was 443.2± 87.5 cGy and 719.4± 243.0 cGy,respectively;the mean D2cc of the sigmoid was 330.3±88.8 cGy and 383.1±105.6 cGy,respectively.In the T&O plans,the doses to the rectum,bladder,and sigmoid were within the limits (rectum:D2cc ≤ 500 cGy;bladder:D2cc ≤ 550 cGy;sigmoid:D2c ≤ 500 cGy),while D2cc of the bladder and sigmoid was higher or partially higher than the limits.T&O plans showed a significant reduction in bladder D2cc and sigmoid D2cc compared with the tandem applicator plans (all P＜0.05).Conclusions Compared with tandem applicator plans,plans using T&O applicator provide significant sparing of bladder and sigmoid tissues in three-dimensional brachytherapy for cervical carcinoma,but the toxicities require further investigation.