Why does a standard immunotherapy work remarkably well for some bladder cancer patients, but fail for others? In this episode, Northwestern Medicine physician-scientist Joshua Meeks, MD, PhD, breaks down his recent research published in the *Journal of Clinical Investigation* and *European Urology* uncovering how the tumor microenvironment and immune cellular communication influence response to Bacillus Calmette-Guérin (BCG) immunotherapy. Find out how single-cell RNA sequencing, macrophage–T-cell interactions, and urinary tumor DNA biomarkers are paving the way for targeted, personalized bladder cancer care.