Side effects are unwanted, undesirable effects caused by cancer treatment that affect healthy tissues or organs. Side effects can range from mild conditions, such as mild headache or feeling sick (nausea), to serious and/or life-threatening conditions. The risk of experiencing side effects varies from person to person. All medicines have the potential to cause side effects. You may want to keep a log of any issue you're experiencing so that you can share them with your doctor. Learn more about the side effects of CALQUENCE (acalabrutinib) for mantle cell lymphoma (MCL) here, and get tips for what to do if you do experience a side effect with CALQUENCE.