Session Item

Adjuvant vaginal cuff brachytherapy (VBT) provides excellent local control in patients with early stage endometrial cancer (EC). Due to the low toxicity reported in EC patients treated with VBT alone, to our knowledge, there are no dose constraints to the organs at risk described in the literature.  We purpose to evaluate toxicity of exclusive VBT in EC patients and to assess its relation with dosimetric parameters.

Eighty-three patients with FIGO Stage I EC treated with VBT alone from 2014 to 2019 were retrospectively analyzed. All patients underwent total hysterectomy and bilateral salpingo-oopherectomy ± lymph node dissection followed by VBT 21Gy/3 fractions to the upper ⅓ of the vagina (4 cm) at 5 mm depth, delivered weekly. Gastrointestinal (GI) and genitourinary (GU) toxicity was evaluated using Common Terminology Criteria for Adverse Events (CTACE) version 4.0 and classified into acute and late according to whether they appeared before or after 6 months of VBT. Maximum dose (Dmax) and dose received by 2 cc(D_2cc) of bladder and rectum were collected and descriptive analysis was performed. Chi Square test was used to assess the impact of dosimetric parameters on toxicity. Overall survival was calculated using Kaplan-Meier plots.

Median age was 68. Thirty-five patients (42,2%) were FIGO Stage IA and 48 (57,8%) stage IB. With a median follow-up of 36 months acute GI and GU grade 1 toxicity was presented in 13 patients (15,7%) and 36 (43,4%), and grade 2 in 4 patients (4,8%) and 1 (1,2%) respectively. One patient (1,2%) presented grade 3 acute GI toxicity (fecal urgency due to proctitis) and 2 patients (3,6%) developed grade 3 acute GU toxicity (urinary incontinence). Late GI and GU grade 1 toxicity was presented in 15 patients (18, 7%) and 37 (44, 6%), and grade 2 in 2 patients  (3,6%) and 5 (6%) respectively. One patient (1, 2%) had grade 3 late GU toxicity (urinary incontinence) (Fig 1). Grade 1 vaginal stenosis was developed in 16 patients (19,3%) and grade 2 in 1 (1,2%). Four patients presented (4,9%) chronic dyspareunia. Median Dmax and D_2cc in rectum were 6.43Gy (IQR: 5,54- 7,14) and 4,46 (IQR: 3,71- 5,01) respectively, and median Dmax and D_2cc in bladder were 6.68Gy (IQR: 6,05-7,47) and 5.29 (IQR: 4,70-5,68).

Statistically significant association was observed in both acute (p=0.048) and late (p= 0.05) GU toxicity with bladder Dmax > 7.46Gy and D_2cc > 5.67Gy. Patients who presented grade 3 GU toxicity were in the highest Dmax and D_2cc quartile. No significant association was observed in acute or late GI toxicity with rectal doses.

Local and distant recurrence rate was 3,6% and 4,8% respectively, and overall survival was 91%.

Our results suggest that bladder Dmax > 7.46Gy and D_2cc > 5.67Gy might be associated with acute and late GU toxicity in EC patients treated with VBT alone. However, no relation was found between GI toxicity and rectal doses. A larger prospective study would be neccesary to confirm the predictive value of these parameters.