Cancer, also known as “malignant tumor”, is the second threatening illness to the human next to the cardiovascular diseases; and is even the first major cause of death in Taiwan. The malignant tumor cells are a group of uncontrolled cells with rapidly abnormal proliferation. During the proliferation process, they tend to invade health tissues nearby. Furthermore, the malignant tumor cells can "break away", "leak", or "spill" from a primary tumor, enter lymphatic drainage and blood vessels, circulate through the bloodstream, and settle down to grow within normal tissues elsewhere in the body (metastasis).

The cancer cells take away nutrition from the normal cells and grow, generate, spread, proliferate and destroy other tissues unceasingly; finally, the body fails to function normally and die. Current anti cancer therapies include surgical operations, chemotherapy, radiotherapy, immunologic therapy, hormone therapy, and target therapy. To avoid the cancer diffusion, metastasis or recurrence, patients would receive chemotherapy and radiotherapy before and after the operation as part of the standard treatment. However, chemo/radiotherapy would inevitably destroy the patients’ immune system as a severe side effect and reduce quality of life.