Cancer and its treatment may have many side effects, according to the Centers for Disease Control, including a decrease in white blood cells, fluid buildup, hair loss, nausea and vomiting, hindered memory, pain, nerve damage, and atrophy or deconditioning, general decline, and blood clots. Many of these things are side effects of the treatment more than the cancer. A side effect occurs when treatment damages healthy cells. Side effects can be different for each person, and for different medicines and kinds of treatment.