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

Radiotherapy induced ureteric stenosis in locally advanced cervical cancer: A review of current evidence

BACKGROUND

Concurrent chemo-radiation followed by high dose rate brachytherapy is the standard of care for locally advanced cervical cancer. The proximity of the ureters to the tumor volume risks ureteric stenosis. Here we outline the current understanding of radiotherapy induced ureteric stenosis in patients treated for cervical cancer, focusing on the incidence, risk factors, clinical consequences, and management.

METHODS

Searches on EMBASE, PubMed, Science Direct, and Google Scholar were performed for publications reporting on radiotherapy, cervix cancer and ureteric stenosis. Multi and single center, prospective/retrospective, cohort, and cross-sectional studies were included.

RESULTS

This narrative review identified key issues relevant to radiation induced ureteric stenosis in cervical cancer in the literature. Thirteen studies were evaluated, identifying crude and actuarial rates of ureteric stenosis of 0.3-13.5% and 1.5-4.4% (at 5 years) respectively. The risk of ureteric stenosis is highest in the first 5 years after radiotherapy but continues to occur at a rate of 0.15% per year. Risk factors including advanced FIGO stage, tumor size >5 cm and baseline hydronephrosis increase the incidence of ureteric stenosis. EQD2 doses of ≥ 77Gy were significantly associated with ≥grade 3 ureteric morbidity. The majority of patients were managed with nephrostomy +/- ureteric stent insertion, with some requiring ureteral reimplantation, urinary diversion or nephrectomy.

CONCLUSIONS

This review has identified multiple considerations, highlighting the need to identify patients highest at risk of ureteric stenosis. There is also a need to recognize ureters as organs at risk, record dose exposure, and apply dose constraints, all of which set the landscape for allowing dose optimization.

Iodine-125 brachytherapy for a desmoid tumor in the abdomen-thorax: A retrospective study

PURPOSE

To investigate the safety and efficacy of iodine-125 seed implantation in the treatment of abdomen-thorax desmoid tumors (DTs).

METHODS AND MATERIALS

Data from 14 DT patients who received brachytherapy with iodine-125 seeds were retrospectively collected from 2014 to 2020. The operation was completed using CT guidance and the treatment plan system (TPS). The number of lesions and the target dosimetry parameters were recorded. After brachytherapy, the lesions were evaluated using response evaluation criteria in solid tumors (RECIST).

RESULTS

Fourteen patients with 18 lesions were enrolled in this study; eleven lesions were in the thorax, seven were in the abdomen, and the lesion gross tumor volume (GTV) was 82.10 cc (interquartile range [IQR]: 40.37, 203.42 cc). The median number of seeds was 88 (IQR: 35, 158), and the median prescription dose was 120 Gy (IQR: 115, 120 Gy). The D90 was 123 ± 16.7 Gy, the V90 was 97% (IQR: 95.00, 97.25%), and the V200 was 27% (IQR: 14.50, 33.00%). The median follow-up time for each lesion was 34 (IQR: 23, 67) months, and the local response rate was 100%. Following brachytherapy, the overall survival was 52.3 ± 30.72 months. One year after brachytherapy, one patient experienced persistent worsening of a brachial plexus injury; another received a ureteral stent. No brachytherapy-related complications were observed in the remaining patients.

CONCLUSIONS

Iodine-125 brachytherapy is a novel treatment option for DT of the abdomen and thorax. Although it is a safe and effective treatment, the radiation dose of iodine-125 brachytherapy for DT-embedded organs at risk must be investigated further.

Can we reduce dose to ureters as avoidance organs for MRI based brachytherapy for cervical cancer? A dosimetric feasibility study

BACKGROUND AND PURPOSE

Ureteral stenosis (US) is an underreported complication of brachytherapy (BT) for cervical cancer (CC), with limited data on toxicity risk reduction. A previous study demonstrated ureter EQD2 D0.1cc > 77 Gy correlated with US development. We sought to assess feasibility of this constraint while maintaining similar HR-CTV coverage.

MATERIALS AND METHODS

Patients with locally advanced CC treated with EBRT plus HDR MRI-based brachytherapy boost without hydronephrosis at diagnosis and with ureter dose EQD2 D0.1cc > 77 Gy were included. Replan was attempted to achieve HR-CTV D90 ≥ 80-85 Gy and ureter dose reduction. Ureter distance from lateral margin of HR-CTV and tandem was recorded. t-test was performed to compare ureteral dose and HR-CTV D90.

RESULTS

Of 25 patients were identified. Hundred percent received 45 Gy in 25 fractions to the pelvis ± paraaortic lymph nodes and 80% receiving median additional parametrial dose of 5.4 Gy. Replan meeting ureteral dose of ≤77 Gy was feasible in 18 of 25 patients, with a reduction in median ureter D0.1cc from 82.3 to 76.8 Gy (p < 0.001). Median HR-CTV D90 was similar (84.7 vs. 85.0 Gy). Replan achieved D0.1cc ≤77 Gy in 56% of patients who experienced US. All unilateral US cases occurred in the ureter closest to HR-CTV.

CONCLUSIONS

Optimization to reduce ureter dose to ≤77 Gy is feasible when ureters are visible and contoured. Ureters may be considered as potential OAR during MRI-based brachytherapy treatment. Reduced ring to tandem total reference air kerma (TRAK) ratio may provide an additional metric by which to lower US risk.