Natural history, response to systemic therapy, and genomic landscape of plasmacytoid urothelial carcinoma

Abstract

Background Plasmacytoid urothelial carcinoma (PUC) is a rare, aggressive histologic variant of urothelial cancer characterised by a diffuse growth pattern and CDH1 mutation. We studied the efficacy of preoperative platinum-based chemotherapy in nonmetastatic PUC and immune checkpoint inhibitors (ICIs) in advanced PUC. Methods Cases of nonmetastatic PUC and advanced PUC treated with ICIs at our institution were identified. Outcomes were compared to those of a published cohort of patients with urothelial carcinoma not otherwise specified. Results We identified 81 patients with nonmetastatic PUC. Of the patients with localised disease who underwent neoadjuvant chemotherapy, pathologic complete response and downstaging rates were 12 and 21%, respectively. Pathologic downstaging was not associated with significant improvement in clinical outcomes. Up to 18% of localised disease and 28% of locally advanced cases had unresectable disease at the time of surgery. ICI-treated advanced PUC (N = 21) had progression-free and overall survival of 4.5 and 10.5 months, respectively, and a 38% response rate. FGFR3 and DNA damage response gene alterations were observed in 3 and 15% of cases, respectively. Conclusions PUC is associated with high disease burden and poor chemosensitivity. Increased awareness and recognition of this disease variant will allow for new treatment strategies.