Plasmacytoid variant urothelial carcinoma: Clinicopathologic outcomes and experience with neoadjuvant chemotherapy.

Abstract

483 Background: Plasmacytoid variant histology is a rare variant that is often locally advanced at diagnosis. Data is limited to small series and the ideal treatment remains unknown. Here we report the clinicopathologic features and outcomes of 29 patients with plasmacytoid variant histology, including 12 patients treated with neoadjuvant chemotherapy (NAC) and 4 with adjuvant or salvage immunotherapy. Methods: All cystectomies performed from 2011-2018 at our institution were reviewed. Patients with plasmacytoid features on transurethral resection or cystectomy were included. Categorical variables were compared using chi-squared tests and survival outcomes were analyzed with log-rank analysis. Results: A total of 993 patients underwent cystectomy for malignancy. Of these, 29 patients (2.9%) had plasmacytoid variant features. At cystectomy, 65.5% were ≥ pT3, 48.2% were node positive, and 13.8% had positive soft-tissue margins. Twelve patients died during the observed period (41.4%), with a median time to death of 7.2 months. Among surviving patients, median follow-up was 21.9 months. Of the 4 patients with positive margins, survival was significantly worse than those with negative margins (p<0.005); all 4 died with a median survival of 1.8 months. Cisplatin based NAC was given to 12 patients (41.4%). NAC was not associated with a survival benefit over cystectomy alone (median survival 27.7 and 51.9 months, respectively; p=0.07), complete response (pT0), or organ confined disease (< pT3). Four patients (13.8%) received adjuvant or salvage checkpoint inhibitors; all surviving with a median follow-up of 28.7 months. Conclusions: Consistent with prior reports, plasmacytoid variants were uncommon and locally advanced. While our rate of positive margins was lower than in previous series, patients with positive margins universally did poorly. NAC was not associated with improved survival or pathologic outcomes. Our findings suggest plasmacytoid variants may not respond well to NAC, though no definitive conclusions can be drawn due to the small number of patients and retrospective design.