Feasibility of ureter delineation and dose recording in the assessment of ureteric stenosis during brachytherapy for cervical cancer

Ureteric stenosis is the commonest complication to affect the ureter after radiotherapy for cervical cancer; despite this ureters are not contoured as organs at risk and limited dosimetric data exist for them. Bilateral ureters were retrospectively delineated on brachytherapy planning imaging for patients treated for cervical cancer between 2014 and 2019. Ureteric stenosis toxicity data and D2cc, D1cc, D0.1cc of the right and left ureter were collated. Ureter V80, V100, V120, and V150 were also analyzed. Univariate analysis was performed to identify predictors of high ureter dose and ureteric stenosis. 95 patients were identified and 190 ureters contoured on brachytherapy planning imaging, with a median follow-up duration of 24 months (IQR23.7). 4.2% (4) of patients had grade 3/4 ureteric stenosis. Mean ureter D0.1cc, D1.0cc and D2.0cc on the right were 80.4Gy (±28.9), 56.2Gy (±7.2) and 52.8Gy (±7.6), and on the left were 75.6Gy (±14.6), 54.3Gy (±5.5) and 52.7Gy (±5.5) respectively. Significantly higher ureter doses were present in patients with baseline hydronephrosis (p < 0.002) and interstitial needle use (p = 0.047). Ureters affected by ureteric stenosis received D0.1cc doses between 60-98Gy. 10-14% received point doses in excess of 150% of the prescribed dose (7Gy) with no resulting ureteric stenosis. No significant difference in D0.1cc was found in patients with or without ureteric stenosis. It is feasible to accurately contour ureters on brachytherapy planning imaging. Baseline hydronephrosis and interstitial needle use contribute to higher ureter doses. No association between dose and ureteric stenosis was found.