Chemotherapy drugs are mostly cytotoxic and can be difficult for patients to tolerate when used uninterrupted for long periods of time. This is because chemotherapy not only kills cancer cells, but also affects normal cells, leading to a decrease in white blood cells and platelets, and normal cells of the gastrointestinal tract may also be damaged. The reason for leaving a certain amount of time between cycles of chemotherapy is to ensure that normal cells have time to recover so that patients can tolerate it.
Because in general, gastric cancer cells grow at a slower rate than the renewal of white blood cells, platelets, and normal cells of the gastrointestinal tract, cancer cells do not grow and proliferate excessively during the interval between chemotherapy treatments while normal cells recover rapidly, which allows for anti-cancer efficacy to be notably affected with improved patient tolerance.
It is important to note that even in the interval, patients tend to be less fit and immune. It is important to avoid exertion and heavy physical labor at this time. Patients should rest, exercise appropriately, and live a regular life. (Cheng Yu, Department of Medical Oncology, The First Hospital of China Medical University, participated in the answer)