LAUSR

PURPOSE This retrospective study aims to assess factors associated with the occurrence of toxicity after brachytherapy (BT), as boost after external beam radiotherapy (EBRT) for treatment of invasive cervix carcinoma. METHODS AND MATERIALS All consecutive patients diagnosed with cervical carcinoma, and treated with concurrent radiochemotherapy from August 2017 to January 2020 were retrospectively included. An isodose conformation index (ICI) was developed to assess the percentage of the prescription isodose contained within the intermediate risk clinical target volume (IR-CTV). RESULTS Eighty-one patients with invasive cervix carcinoma from stage IB to stage IVa were included. Thirty-two (40%) and 49 (60%) patients were treated with Pulsed Dose Rate (PDR) and High Dose Rate (HDR) BT, respectively. Median follow-up was 19.6 months (5.6-41.2). The main factors associated with development of gastrointestinal toxicity were: the median volume of the prescription isodose (67.9cm[3] [37.6-92.9] vs. 49.1cm[3] [34.5-53.5], p = 0.05), the value of ICI (59% [51%-83%] vs. 86% [65%-96%], p = 0.01), the median equivalent dose delivered to the sigmoid (D2cc= 58.4 GyEQD2 [53.9-61.1] vs. 55.2 GyEQD2 [52.8-57.5], p = 0.06) and the median equivalent dose delivered to the IR-CTV (D90= 63.9 GyEQD2 [60.6-66.4] vs. 61.2 GyEQD2 [59.4-64.5], p = 0.03). The proportion of patients who received EBRT lymph node boost was higher in patients who developed urinary toxicity than in patients who did not (57.1% vs. 28.6%, p = 0.08). Anticoagulant (p = 0.02) and antiaggregant therapy (p = 0.01) were associated with occurrence of both urinary and gastrointestinal toxicity. CONCLUSIONS Our study confirms the predictive value of irradiated volume in the occurrence of gastrointestinal toxicity, as well as the need for a better conformation to the target volume. Precautions should be considered in patients with vascular comorbidities.