Postoperative endometrial cancer treatments with electronic brachytherapy source

Abstract

PurposeThis study is a dosimetric and acute toxicity comparison of endometrial cancer patients treated with either Axxent (Xoft, Inc., San José, CA, USA) electronic and interstitial brachytherapy versus interstitial high dose rate brachytherapy (HDRBT).Materials and MethodsBetween 2015 and 2017, 94 patients with postoperative endometrial cancer were treated in our centre with the Axxent electronic brachytherapy (eBT) system. The V150 and V200 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 D2cc, V50% and V35%. 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.ResultsThe 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 D2cc versus 70.1% for HDRBT Ir-192, for V50% was 7.2% versus 12.7% and for V35% was 15.2% versus 28.2%. In rectum the D2cc was 61.2% versus 68.4%, for V50% was 7.9% versus 14.3% and for V35% 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.ConclusionsThe 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 V150 and V200 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.

Treatment of cervical cancer with electronic brachytherapy

“…The eBT device is a useful addition in centers with an HDR device. Its mobility and versatility mean that it can be used as a complementary facility to treat cervical cancer and for intraoperative radiotherapy in breast cancer, in skin cancer, and in postoperative treatment of endometrial cancer …”

“…In our study, we did not modify treatment owing to differences in RBE with respect to Ir192 because of the good results achieved with treatment administered to the endometrium and the contradictory results reported in several published studies. Modification of the prescribed dose continues to be controversial in low‐energy cases …”

“…A lower dose was always found in the OAR in patients whose planning was based on eBT, although the patients in those studies were treated with Ir192. Another study comparing patients with endometrial cancer treated with eBT has reported favorable preliminary results …”

Electronic brachytherapy for gynecological cancers — a systematic review

“…Toxicity was scored according to Radiation Therapy Oncology Group — European Organization for Research and Treatment of Cancer (RTOG-EORTC). There was 1 (1.1%) acute G2 event and 1 month after treatment there were none [ 37 ].…”

Feasibility of electronic brachytherapy in cervix cancer–A dosimetric comparison of different brachytherapy techniques

“…Modification of the prescribed dose continues to be controversial in lowenergy cases ( 32 ). We based our approach on previous experience in that the prescription dose was not modified owing to differences in RBE with respect to 192 Ir, and good results were obtained with eBT in endometrium ( 33 ) and cervical cancer ( 19 ). Similarly, a clinical study showed that modifying the prescription dose by including the RBE factor for treatment of nodular and superficial basal cell carcinoma using eBT reduced the control of the tumor from 95%-90% ( 34 ).…”