Introduction: Collecting duct carcinoma (CDC) is a rare renal malignancy. We relied on a large population-based cohort to address epidemiology, clinical characteristics, and treatment of CDC patients. We also tested survival in the overall cohort, as well as in stage-specific fashion.
Materials and methods: Within Surveillance, Epidemiology, and End Results (2004-2018) database, we identified 399 CDC patients. Based on Kaplan-Meier plots survival estimates, conditional survival rates were derived according to disease stage. Cox regression models tested for predictors of cancer specific mortality (CSM).
Results: Overall, 273 (68.4%) patients were male, 236 (59.2%) had T3-4 stages, 148 (37.1%) had lymph node invasion, and 156 (39.1%) had distant metastases at initial diagnosis. Nephrectomy alone was commonest in stage I-II (n = 91/99, 92%) and III (n = 94/116, 81%). Combination of both nephrectomy and systemic therapy was commonest in stage IV (n = 62/172, 36%). In the overall cohort, median cancer specific survival was 18 months. Provided a disease-free interval of 24 months, five-year Kaplan-Meier estimated survival at diagnosis increased from 74.2 to 91.0% in stage I-II, from 31.1 to 65.3% in stage III, and from 6.3 to 34.1% in stage IV. In multivariable Cox regression models addressing CSM, systemic therapy (Hazard Ratio [HR]: 0.47, P = 0.020), nephrectomy (HR: 0.37, P < 0.001) and combination of both (HR: 0.28, P < 0.001) exhibited a strong protective effect.
Conclusion: Despite its highly aggressive phenotype and dismal survival, CDC is sensitive to nephrectomy and/or systemic therapy. Moreover, even for advanced stage, a more favorable prognosis can be achieved in patients, who benefit of disease-free interval after diagnosis and initial treatment.
Keywords: Collecting duct carcinoma; Conditional survival; RCC; SEER; Variant histology.
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