This study is testing a new way to treat High-Risk Non-Muscle Invasive Bladder Cancer (HR NMIBC). This is a type of bladder cancer that stays in the bladder lining and doesn't spread to the muscle. The study looks at combining two treatments: pembrolizumab, a medicine that helps the immune system fight cancer, and Bacillus Calmette-Guerin (BCG), a vaccine used to treat bladder cancer. The goal is to see if patients taking both medicines live longer without cancer growing or returning, compared to those taking only BCG.

• The study involves regular visits to the clinic for treatment and check-ups.
• There may be side effects from treatments; your doctor will monitor and manage them.
• You might be eligible for compensation for your participation.

Participants must have HR NMIBC and have had certain tests and treatments before joining. You cannot join if you have advanced bladder cancer, certain other health conditions, or have had certain treatments recently. If you are interested, talk to your doctor about whether this study might be right for you.