Leukemia is a type of blood cancer that affects the bone marrow and lymphatic system. Chemotherapy as a drug treatment method is one of the popular ways of treating this disease to destroy fast-growing cells. In this paper, the finite-time adaptive integral fast terminal sliding mode control (AIFTSMC) as a robust strategic method for treating leukemia cancer based on the chemotherapy process has been introduced. Two different treatment modes called uniform and non-uniform have been investigated in detail. Our goal in this trial is to reduce the number of cancer cells during treatment while minimizing damage to healthy cells. Moreover, the controller's coefficients in the sliding surface have been optimized using the water cycle algorithm, a novel type of metaheuristic algorithm. The simulation results show that AIFTSMC effectively targets cancer cells while minimizing damage to healthy cells. The results promise a novel and practical way to treat leukemia in clinical applications.