Pathological and oncological outcomes in patients with sarcomatoid differentiation undergoing cystectomy

Objective To evaluate whether urothelial carcinoma (UC) with sarcomatoid differentiation is associated with a lower pathological response rate to neoadjuvant chemotherapy (NAC) and worse oncological outcomes compared to UC without variant histology among patients undergoing radical cystectomy. Patients and Methods Patients with UC undergoing cystectomy from 1995 to 2018 at the Memorial Sloan Kettering Cancer Centre were identified. Patients with sarcomatoid differentiation at transurethral resection (TUR) or cystectomy, and patients without variant histology were selected. Downstaging from >= cT2 to <= pT1N0 defined partial response and pT0N0 defined complete response. Recurrence-free, cancer-specific and overall survival were modelled. Results We identified 131 patients with sarcomatoid differentiation and 1722 patients without variant histology, of whom 25 with sarcomatoid histology on biopsy and 313 without variant histology received NAC. Those with sarcomatoid differentiation presented with higher consensus tumour stage (94% >= T2 vs 62%; P < 0.001) and were, therefore, more likely to receive NAC (29% vs 18%; P = 0.003). We found no evidence to support a difference in partial (24% vs 31%) or complete (20% vs 24%) response between patients with sarcomatoid histology and those with pure UC at TUR (P = 0.6). Among patients with sarcomatoid differentiation, 5-year recurrence-free survival was 55% (95% confidence interval [CI] 41-74) among patients receiving NAC and 40% (95% CI 31-52) among patients undergoing cystectomy alone (P = 0.1). Adjusting for stage, nodal involvement, margin status and receipt of NAC, sarcomatoid differentiation was associated with worse recurrence-free (hazard ratio [HR] 1.82, 95% CI 1.39-2.39), disease-specific (HR 1.66, 95% CI 1.23-2.22), and overall survival (HR 1.37, 95% CI 1.06-1.78). Conclusions Sarcomatoid differentiation was associated with higher stage at presentation and independently associated with worse survival. Given similar pathological response rates if sarcomatoid differentiation is detected at initial resection, and greater survival among patients receiving NAC, treatment with NAC appears warranted. Other drivers of the poor outcomes of this histology must be investigated.