Postoperative endometrial cancer treatments with electronic brachytherapy source

Abstract

Purpose This study is a dosimetric and acute toxicity comparison of endometrial cancer patients treated with either Axxent (Xoft, Inc., San Jose, CA, USA) electronic and interstitial brachytherapy versus interstitial high dose rate brachytherapy (HDRBT). Materials and Methods Between 2015 and 2017, 94 patients with postoperative endometrial cancer were treated in our centre with the Axxent electronic brachytherapy (eBT) system. The V 150 and V 200 are evaluated prospectively for each plan. The mean age of patients was 65.9 years (age range 33–84 years), with different tumour staging. Of the 94 patients, 37 received exclusive adjuvant brachytherapy (25 Gy in five sessions); the remaining patients received external beam radiotherapy (EBRT) with a regimen of 23 sessions of 2 Gy each to the entire pelvis, followed by eBT (15 Gy in three sessions). Additionally, the absorbed doses received by the organs at risk (OAR), urinary bladder, rectum and sigmoid colon were compared with HDRBT plans, evaluating D 2cc , V 50% and V 35% . Median follow-up was done for each of the 94 patients to assess the toxicity of the treatment: vaginal mucosa toxicity, rectal and urinary toxicity; and results are presented for acute toxicity, toxicity at 1 month after the end of treatment and follow-up after 12 months for a portion of patients according to the Radiation Therapy Oncology Group (RTOG) toxicity criteria. Results The doses in OAR for eBT plans were lower than that for HDRBT plans, both Ir-192 and Co-60 plans, whose doses were similar. The dose in bladder with eBT was 63.8% of the prescribed dose for D 2cc versus 70.1% for HDRBT Ir-192, for V 50% was 7.2% versus 12.7% and for V 35% was 15.2% versus 28.2%. In rectum the D 2cc was 61.2% versus 68.4%, for V 50% was 7.9% versus 14.3% and for V 35% was 16.7% versus 32%. Results demonstrated lower doses to OAR in all eBT plans. Acute toxicity in eBT was very low in cases of mucositis, with only one case of toxicity greater than grade 1, rectal toxicity and urinary toxicity; results at 1 month are equally good, toxicity symptoms disappeared and no relapses have occurred to date. Conclusions The results of treatment with the Axxent eBT unit for 94 patients are very good, as no recurrence has been observed and the toxicity of the treatment is very low. The increase in V 150 and V 200 has not produced an increase in vaginal mucosa toxicity, and the doses in the OAR are lower than in the plans implemented for HDRBT with Ir-192 or Co-60. eBT is a good alternative to treat endometrial cancer in centres without conventional HDR availability. To date, there are limited published studies reporting on outcomes from patients treated with eBT.