Comparison of two ICI-based microtubule antagonist therapies for high-risk, non-muscleinvasive bladder cancer

e14629 Background: Patients with highly extensive non-muscle-invasive bladder cancer (NMIBC) whose invasion area is too vast to be removed through TURBT should receive radical cystectomy in clinical practice. Clinical practice showed that nab-paclitaxel (Nab-P) or RC48-ADC (Disitamab Vedotin, DV) in combination with tislelizumab (BGB-A317, immune checkpoint inhibitor, ICI) had good effects on these patients with acceptable adverse events (AEs). This study was to compare the efficacy and safety of these two regimens. Methods: Retrospectively collected and analyzed data from two single-center clinical trials. Eligible patients were aged 18 years or older with unresectable NMIBC who received their first dose of Nab-P/ICI or DV/ICI between July 2020 and December 2022. The primary outcome was the pathological complete response (pCR) rate in a propensity score matching (PSM) population that was performed matching using a 1:4 ratio for the DV/ICI and Nab-P/ICI groups by propensity score. The main secondary outcome was treatment-related adverse events (trAEs), assessed in all eligible populations. Results: The eligible population was 12 for DV/ICI and 69 for the control group (Nab-P/ICI). The PSM population was 12 for DV/ICI and 48 for Nab-P/ICI. pCR was 66.7% (39.1%-86.2%) for DV/ICI and 60.4% (46.3%-72.9%) for the Nab-P/ICI group (OR: 0.76; 95% CI: 0.23–2.78; Fisher's exact test P = 0.75) in the PSM population. The most common trAE in the Nab-P/ICI group was alopecia, and the incidence was significantly lower in DV/ICI (Fisher's exact test, P < 0.05). Grade 3–4 trAEs were observed at 8.70% and 8.33% in Nab-P/ICI and DV/ICI, respectively. No trAE-related deaths were reported. Conclusions: The pooled results of the two studies with the efficacy and safety data showed promising ICI-based microtubule antagonist regimens in pts with highly extensive non-muscle-invasive bladder cancer (NMIBC), and DV/ICI may be preferred by pts for the low incidence of alopecia in clinical practice.