Understanding Hydronephrosis Occurrence by an Individual-Kidney Level Analysis of all Events Postchemoradiation...

Hydronephrosis is a complex renal abnormality that requires assessment of individual-kidney status at different times for correct interpretation of the mechanism of damage. This study analyzes all hydronephrosis events in women with locally advanced cervical cancer.

The status of 449 kidneys from 225 women treated with external beam radiation therapy (RT) with concurrent cisplatin and image guided adaptive brachytherapy were retrospectively reviewed. Hydronephrosis incidence, causes (including radiation-induced hydronephrosis [RIH]), associated factors, and resolution rates were analyzed. Univariable and multivariable analyses were performed at the individual-kidney level, clustered by individual patient.

At baseline, 10.9% (49/449) of the kidneys were affected by hydronephrosis, which resolved in 38.8% (19/49) after RT. During follow-up, new hydronephrosis occurred in 15.8% (71/419) of the kidneys, caused more frequently by cancer recurrence than by RIH (2:1 ratio). The overall RIH incidence per kidney was 5.7% (95% CI, 3.2-8.1) and 7.2% (95% CI, 3.8-10.4) at 3 and 5 years, respectively. The rates of type A RIH (ureteral stenosis) at 3 and 5 years were 1.9% (95% CI, 0.5-3.3) and 3.5% (95% CI, 0.8-6.2). Both 3- and 5-year rates of type B RIH (damage to structures other than ureter) were 3.8% (95% CI, 1.7-5.9). Point A dose (P = .01; EQD2₃), bladder D_2.0cc (P = .03; EQD2₃), and high-risk clinical target volume (P < .01; cm³) were associated with overall hydronephrosis incidence in the multivariable model. Point A dose was associated with type A RIH (P < .01) but not with type B (P = .74). At last follow-up, 19.6% (88/449) of kidneys had unresolved hydronephrosis.

Persistent hydronephrosis is not uncommon after definitive RT for locally advanced cervical cancer (20%), with RIH being a relevant etiology at 5 years (7%). In contrary to type B RIH (damage to other structures), type A (ureteral damage) is usually unilateral, associated with dose to the ipsilateral point A, and its incidence does not plateau over time.