The effect of number of treatment cycles of platinum-based first-line chemotherapy on maximum radiological response in patients with advanced urothelial carcinoma

•We retrospectively evaluated 167 patients with advanced urothelial carcinoma treated with platinum-based first-line chemotherapy to investigate the number of cycles associated with the maximum radiological response and progression disease rate.•The maximum radiological response was observed at Cycles 2.•The radiological response was significantly different between Cycle 2 and 4.•We observed 63% of patients with disease progression within the first 4 cycles•Our results suggested that less than half of patients were a potential candidate for maintenance immunotherapy after the first 4 cycles. The number of cycles of platinum-based first-line chemotherapy associated with the maximum tumor response in patients with advanced urothelial carcinoma is not yet established. We investigated the association between the number of cycles and the maximum radiological response of first-line chemotherapy. We retrospectively evaluated 167 patients with advanced urothelial carcinoma treated with platinum-based first-line chemotherapy between May 2003 and December 2020. The primary outcome was estimating the number of cycles associated with the maximum radiological response and progression disease rate within the 6 cycles. The radiological response was evaluated by the RECIST v1.1. The secondary outcomes included the difference in radiological response rate and the impact on overall survival between the cisplatin-based and carboplatin-based regimens. The maximum radiological response was -22% at Cycles 2. It was significantly decreased at Cycles 4 (-15%) compared with Cycles 2 (P < 0.001). The progression disease rate within the first 2, 4, and 6 cycles were 21% and 63%, and 84%, respectively. Radiological response was no significant difference between the cisplatin-based and carboplatin-based regimens. However, it was significantly decreased in the carboplatin-based regimen at Cycles 4 (-17%) compared with Cycles 2 (-22%; P = 0.004). Background-adjusted overall survival was not significantly different in between the cisplatin-based and carboplatin-based regimens (hazard rate 1.27; P = 0.337). The maximum radiological response was -22% at Cycles 2. The radiological response was significantly different between Cycle 2 and 4. More than half of patients had disease progression within the first 4 cycles. [Display omitted]