Side effects are generally easier to tolerate than those associated with chemotherapy. Our care team will monitor your response to the treatment and manage any reactions or complications. Side effects can be mild or more severe but are treatable and generally indicate the therapy has activated the immune system to fight the cancer. The most common side effect of CAR T-Cell therapy is called cytokine release syndrome or CRS. It can affect up to 9 in 10 CAR T-Cell patients. It is generally brief, lasting about a week. Many patients liken it to the flu with fever, low energy, and body aches. It is treatable with medication. The other side effect is known CAR T-Cell-related encephalopathy syndrome or CRES. Its symptoms are more severe than those of CRS and may include memory loss or confusion. In rarer cases, they may affect speech. CRES is treatable. Symptoms usually go away after a few days. Stanford has the knowledge and resources to manage these reactions when then they occur.