[CORRELATION BETWEEN RELATIVE DOSE INTENSITY AND TREATMENT OUTCOMES OF ENFORTUMAB VEDOTIN IN PATIENTS WITH LOCALLY ADVANCED/METASTATIC UROTHELIAL CARCINOMA].

(Objective) This retrospective study investigates the correlation between relative dose intensity (RDI) and the clinical efficacy of enfortumab vedotin (EV) in clinical practice. (Subjects and methods) We analyzed 40 patients who received at least two cycles of EV monotherapy for unresectable or metastatic urothelial carcinoma at our hospital between January 2022 and April 2024. RDI was calculated for the total treatment period (Total-RDI) and the first two and four cycles (2-cycle RDI/4-cycle RDI). Patients were then categorized into two groups based on the median RDI; differences in patient characteristics, overall response rate, progression-free survival (PFS), and overall survival (OS) were then evaluated. (Results) The median observation period from the start of EV treatment was 14.1 months, and the median number of treatment cycles was 8.5. The response rate was 55%, with four cases of complete response (CR) and 18 cases of partial response (PR). The median RDI decreased during the first four cycles and then stabilized at approximately 0.6. The median Total-RDI was 0.57. PFS and OS were significantly longer in patients with Total-RDI <0.57 than in those with Total-RDI ≥0.57 (PFS: 16.4 months vs. 6.0 months, p=0.007; OS: not reached vs. 15.1 months, p=0.004). Among patients who responded to EV treatment (n=22), the Total-RDI was 0.49 in the CR group and 0.52 in the PR group, whereas the 2-cycle RDI/ the 4-cycle RDI were 0.62/0.73 in the CR group and 0.71/0.59 in the PR group. (Conclusion) The median RDI of EV treatment decreased over the first four cycles and then stabilized. Of note, a reduction in RDI during the treatment period did not negatively impact treatment efficacy.