Clinical Outcomes in Patients with Micropapillary Urothelial Carcinoma of the Bladder - Expert Commentary

Micropapillary (MP) is a histological variant of bladder cancer. As with most other histological variants of bladder cancer, the available data is derived from small case series and treatment is based on expert opinion. More knowledge about treatment and prognosis of MP UBC is needed to identify the optimal therapy for MP UBC. 

A new paper published by Abufaraj et al. in European Urology conducted a systematic review and meta-analysis of studies examining the clinical outcomes of MP bladder cancer. The authors identified papers using PubMed, Cochrane Library, American Society of Clinical Oncology, European Society for Medical Oncology, and EMBASE databases in June 2018 using words: recurrence-free survival (RFS), cancer-specific survival (CSS), and overall survival (OS). The investigators identified 758 reports including 3154 patients with MP variant. Of these reports, 28 articles were used for qualitative analysis and 15 articles were used for quantitative analysis. 

The authors found that the range of 5-year cancer-specific survival was 81% to 100% in patients who underwent early radical cystectomy (RC) and 60% to 85% for patients treated with transurethral resection of the bladder (TURB).  Complete pathological downstaging (ypT0) was reported in three studies with rates ranging from 11%-55% following neoadjuvant chemotherapy. Two studies showed partial pathological response (pT1)  rate of 55% in two studies. The authors found no improvement in relapse-free survival (hazard ratio [HR] 1.23, 95% confidence interval [CI] 0.52–2.93, p = 0.6), cancer-specific survival (HR 0.9, 95% CI 0.48–1.7, p = 0.8), or overall survival (HR 1.35, 95% CI 0.98–1.86, p = 0.1) in patients who had chemotherapy prior to RC. Among MP bladder cancer patients who underwent RC alone, 53% percent (95% CI 43–63%) had locally advanced disease (pT3), 51% (95% CI 19–83%) had lymphovascular invasion and 43% (95% CI 33–52%) had lymph node metastases.  The authors found that the MP variant was not associated with worse clinical outcomes in comparison to pure urothelial carcinoma. 

The authors conclude that while MP bladder cancer is associated with clinicopathological features of advanced disease, it is not associated with worse survival outcomes in patients undergoing RC. NAC results in pathological downstaging in a significant number of patients but did not translate into better survival outcomes in this retrospective review. As with other rare histological variants of bladder cancer, prospective randomized data is needed to understand the best treatment options.

Written by: Bishoy M. Faltas, MD, Director of Bladder Cancer Research, Englander Institute for Precision Medicine, Weill Cornell Medicine

1. Abufaraj M, Foerster B, Schernhammer E, Moschini M, Kimura S, Hassler MR, Preston MA, Karakiewicz PI, Remzi M, Shariat SF. Micropapillary Urothelial Carcinoma of the Bladder: A Systematic Review and Meta-analysis of Disease Characteristics and Treatment Outcomes. Eur Urol. 2018 Dec 12. pii: S0302-2838(18)30956-4. doi: 10.1016/j.eururo.2018.11.052.

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