Radiother Oncol 2020 Oct 14
Ureteral stenosis after 3D MRI-based brachytherapy for cervical cancer - Have we identified all the risk factors?
Abstract
Background and purpose
Ureteral stenosis (US) is a known complication from image-guided brachytherapy (IGBT); however, no dosimetric parameter has been associated with ureteral toxicity. We aimed to report the rate of late grade ≥3 US after MRI-based IGBT, and to identify clinical factors and dosimetric parameters predictive for US.
Materials and methods
A retrospective review was performed on all cervical cancer patients treated with MRI-based IGBT between 2007 and 2017. Late grade ≥3 US was recorded according to CTCAE 4.03. The minimum dose to the maximally irradiated 0.1 cm3 of ureter (D0.1cm3) was extracted from dose-volume histograms. Binary logistic regression was performed to identify predictors of late grade ≥3 US.
Results
242 patients with a median follow-up of 35.8 months (IQR, 19.2-60.8) were identified. Late grade ≥3 US occurred in 18 patients, and the actuarial 3-year rate was 7.3% (95% CI 3.3-11.3). After excluding patients with pre-existing hydronephrosis, late grade ≥3 US occurred in 11 patients with an actuarial 3-year rate of 4.4% (95% CI 1.7-7.1). Ureters with D0.1cm3 ≥77 Gy had a 28.6% incidence of late grade ≥3 US compared to 7.5% in those with D0.1cm3 <77 Gy (OR 2.39; 95% CI 1.23-4.65; p = 0.01). The incidence of late grade ≥3 US was 33.3%, and 40.0% for ureters receiving ≥85 and ≥90 Gy, to D0.1cm3, respectively.
Conclusion
After MRI-based IGBT, there is an estimated 4.4% risk of developing late grade ≥3 US among patients without pre-existing hydronephrosis. Ureteral dose ≥77 Gy to D0.1cm3 correlates with development of late grade ≥3 US.
Related Questions
For patients with solitary plasmacytoma of the ureter undergoing definitive XRT (40-50 Gy), what dose constraint do you use for the ureter?
Well, since this is a solitary plasmocytoma of the ureter, I presume that parts of the GTV encompass the OAR here. I do not think that you can set any meaningful constraint for the ureter, bearing in mind that this is a serial OAR. You can try to avoid hotspots in the ureter, but that's about it.
For cervical cancer intracavitary brachytherapy, do you use contrast when using CT-based planning to better visualize the ureters?
We normally do MRI based planning and the ureter can be identified and contoured on MRI. For only CT based, we do out diluted contrast in bladder for bladder contouring but do not go to the ureter. Rodríguez-López et al., PMID 33065181Koerner et al., PMID 34980569
For gyn cancers receiving chemoradiation, how high can you boost grossly positive nodes with SIB if not near bowel?
I typically will give a simultaneous integrated boost (SIB) of 60 Gy in 30 fractions to the pelvic and para-aortic nodal CTV, which is the PET positive GTV plus a 3 mm margin. If possible I will boost the GTV of larger gross nodes (>1 cm) to 66 Gy (2.2 Gy/fx) with no margin, if constraints can be me...