This phase II trial studies how well gemcitabine hydrochloride and cisplatin work in treating patients with invasive bladder urothelial cancer. Drugs used in chemotherapy, such as gemcitabine hydrochloride and cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading.

This phase II trial studies the effect of adding pembrolizumab to gemcitabine in treating patients with non-muscle invasive bladder cancer whose cancer does not respond to Bacillus Calmette-Guerin (BCG) treatment. Drugs used in chemotherapy, such as gemcitabine, work in different ways by stopping the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the patient’s immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Adding pembrolizumab to gemcitabine may delay the return of BCG-unresponsive bladder cancer for longer period compared to gemcitabine alone.

This phase II/III trial tests the role of DNA released from tumor cells into the blood in guiding the use of immunotherapy (nivolumab alone or with relatlimab) after surgical removal of the bladder for bladder cancer treatment. DNA is material found inside all of our cells that acts as a blueprint for how cells function. Tumor cells often have abnormal DNA that looks different than DNA in normal cells. A new test called Signatera has been developed that can detect bladder cancer DNA in the blood which might indicate the presence of bladder tumor cells somewhere in the body. Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Relatlimab is a monoclonal antibody that may interfere with the ability of tumor cells to grow and spread. This trial may help doctors determine if the Signatera test can better identify which patients need an additional treatment with immunotherapy to help prevent bladder cancer from coming back after surgery.

The study hypothesis is that BCG naïve non-muscle invasive bladder cancer (NMIBC) patients treated with intravesical Gemcitabine + Docetaxel (GEMDOCE) will result in a non-inferior event-free survival (EFS) compared to standard treatment with intravesical BCG. The purpose of this study is to test whether Gemcitabine + Docetaxel is a better or worse treatment than the usual BCG therapy approach. The primary objective of this study is to determine the event free survival (EFS) of BCG-naïve high grade non-muscle invasive bladder cancer patients treated with intravesical BCG vs Gemcitabine + Docetaxel. Secondary objectives are as follows: to compare changes in cancer-specific and bladder cancer-specific QOL from baseline to treatment between BCG-naïve high grade NMIBC patients receiving BCG and GEMDOCE, to determine the cystectomy free survival (CFS) of BCG-naïve high grade NMIBC patients treated with intravesical BCG vs GEMDOCE, to determine the progression free survival (PFS) of BCG-naïve high grade NMIBC patients treated with intravesical BCG vs GEMDOCE, and to determine the safety and toxicity of BCG-naïve high grade NMIBC patients treated with intravesical BCG vs GEMDOCE.