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Hydronephrosis in Patients with Bladder Cancer Undergoing Chemoradiotherapy - Expert Commentary

Muscle-invasive bladder cancer (MIBC) with hydronephrosis typically warrants radical cystectomy, though the impact of chemoradiotherapy (CRT) on hydronephrosis remains unclear. A recent study evaluated the incidence, etiology, and management of hydronephrosis before and following CRT in patients with MIBC. This retrospective cohort study included 146 patients with MIBC treated with CRT between January 2014 and December 2022. The study analyzed 27 patients (18%) with pre-existing hydronephrosis and 119 patients (82%) without. Hydronephrosis was defined as any grade of renal pelvis dilatation with or without ureteral dilatation on imaging. The mean patient age was 73 years (SD: 8.59), with 74% male patients. Treatment included chemotherapy completion in 93.2% and radiotherapy completion in 99.3% of patients. Most patients (84.2%) received 40 Gy to the whole bladder in 20 fractions with a 15 Gy boost.

In patients with pre-existing hydronephrosis, hydronephrosis persisted after CRT in 74% (20/27 patients). Tumor caused pre-existing hydronephrosis in 93% (25/27) of cases. Among patients without pre-existing hydronephrosis, 21% (25/119) developed hydronephrosis after CRT with a median onset time of 8.7 months (IQR: 5.9-14.6). Tumor was responsible for new hydronephrosis in 44% (11/25) of these patients. Drainage was performed in 44% (12/27) of patients with pre-existing hydronephrosis and 52% (13/25) of patients who developed hydronephrosis. Visual complete resection was significantly associated with decreased hydronephrosis risk (HR=0.24, 95% CI: 0.09-0.62, p=0.003). Median eGFR declined significantly in patients developing hydronephrosis after CRT, from 77.0 to 50.5 mL/min/1.73 m² (p=0.006). The investigators found that drainage requirements were substantial, with permanent drainage in 33.3% (9/27) of patients with pre-existing hydronephrosis and salvage cystectomy in 14.8% (4/27). Among patients developing new hydronephrosis, 44% (11/25) required drainage and 4% (1/25) underwent salvage cystectomy. The 2-year composite outcome-free survival was 0.25 (95% CI: 0.13-0.51) for nephron-sparing perspective and 0.47 (95% CI: 0.30-0.73) for bladder-sparing perspective. Six patients (22%) developed atrophic kidneys after CRT.

These findings suggest that hydronephrosis may be a relative rather than absolute contraindication for CRT in carefully selected patients. Pre-existing hydronephrosis persists after CRT in approximately 75% of patients, while 20% of patients without pre-existing hydronephrosis develop it post-treatment. The high drainage requirements and potential for kidney function deterioration necessitate careful patient counseling regarding nephron-sparing versus bladder-sparing approaches and careful monitoring.

Written by: Bishoy M. Faltas, MD, Chief Research Officer, Englander Institute for Precision Medicine, Gellert Family - John P. Leonard, MD, Research Scholar, Associate Professor of Medicine, Cell and Developmental Biology, Weill Cornell Medicine, New York- Presbyterian Hospital, NY

References:

  1. Remmelink MJ, el Awadly N, Arbeel-Weening B, Nadorp S, Leter MR, Oddens JR, et al. Impact of chemoradiotherapy for bladder cancer on pre-existing hydronephrosis and development of new hydronephrosis. Radiat Oncol. 2025;20:104. doi: 10.1186/s13014-025-02678-9.
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