Re-irradiation with interstitial brachytherapy in uterine cancer patients with vaginal recurrence after post-operative pelvic irradiation

Introduction
This study aimed to evaluate the outcomes and dose-volume parameters of re-irradiation with interstitial brachytherapy (ISBT) in uterine cancer patients with vaginal recurrence after post-operative pelvic irradiation.

Material and methods
We evaluated six uterine cancer patients who received re-irradiation with ISBT between January, 2012 and December, 2016. As an initial treatment, all patients received post-operative whole pelvic irradiation of 45-50.4 Gy in 25-28 fractions. For vaginal recurrence, all patients were treated with ISBT alone at a dose of 38-42 Gy in 6-7 fractions for clinical target volumes (CTVs) for 3-4 days.

Results
Post-operative pelvic irradiation was delivered to five and one patients, using a three-dimensional conformal technique and intensity-modulated radiotherapy, respectively. Median duration from surgery to vaginal recurrence was 25.7 months. Median tumor size just before ISBT was 3.3 cm. Median time from completion of pelvic irradiation to ISBT initiation was 24.1 months. Mean doses per fraction of ISBT for CTV D90 (the minimum dose received by 90% of CTV) and minimum dose received by 2cc (D2cc) for the bladder and for rectum were 6.1 Gy, 4.4 Gy, and 3.8 Gy, respectively. Mean total equivalent dose in 2 Gy fractions (EQD2), including external beam radiotherapy and ISBT, for D2cc for the bladder, sigmoid, and rectum were 92.1 Gy, 50.4 Gy, and 81.6 Gy, respectively. Median follow-up duration was 53.3 months. Local recurrence was observed in two patients, and four of the six patients were alive. Grade 2 late rectal complications occurred in two patients, and no late grade ≥ 3 complications were observed in four alive patients.

Conclusions
Re-irradiation with ISBT may be an effective treatment strategy for gynecological cancer patients with vaginal recurrence after post-operative pelvic irradiation.