Cancer immunotherapy ranked No. 1 on Science magazine’s annual list of the top 10 scientific breakthroughs of 2013. Exactly how many patients, and which ones, would benefit from immunotherapy, and which ones would benefit the most, scientists don’t yet know. Scientists are busy trying to discover the biomarkers that will provide answers and thinking of ways to make treatments more effective. But a new chapter in cancer research and treatment has opened. Traditional therapies include surgical resection, chemotherapy, and radiation therapy. They have limitations: surgical resection is often limited by the invasion and spread of cancer cells to adjacent tissues or distant metastases; chemotherapy is limited by its toxicity to other normal tissues in the body; and radiation therapy can also cause damage to normal tissues. All conventional therapies are extremely burdensome to the body and are very difficult to cure completely after malignant metastasis occurs, regardless of the modality. Targeted therapy emerged at the end of the 20th century. Targeted therapy is designed at the cellular molecular level to target cancer-causing sites, and the drugs enter the body to specifically select cancer-causing sites for combined action, causing specific death of tumor cells without harming the normal tissue cells around the tumor. These drugs include small molecule targeted drugs and monoclonal antibodies. Small molecule targeted drugs: target the links that may lead to cell carcinogenesis, such as abnormal cell signaling pathways, overexpression of certain receptor proteins, anti-tumor angiogenesis, etc., to reverse these malignant biological behaviors at the molecular level, thus inhibiting tumor cell growth. Monoclonal antibodies: induce the body to produce antibody-dependent cell-mediated cytotoxic effects; act as a vehicle for targeted therapy to specifically deliver cytotoxic substances such as chemotherapeutic drugs, radioisotopes and toxins to the target site, while selectively killing the target cells. However, there are shortcomings of targeted drugs: mainly, the effectiveness of molecular targeted drugs is low, and a certain drug can only work on specific mutated genotypes of tumors; tumor gene mutations produce drug tolerance leading to long-term treatment effect; there are serious adverse effects; some tumors cannot be effectively treated by targeted drugs. Immunotherapy The latest tumor immunotherapy is to control and kill tumor cells by mobilizing the body’s immune system and enhancing the anti-tumor immunity of the tumor microenvironment. Preliminary clinical studies have demonstrated the effectiveness of immunotherapy in advanced tumors. Studies at Yale University and other institutions have shown impressive long-term survival data after treatment with Bristol-Myers Squibb immune test site monoclonal antibody nivolumab, with 62% of patients surviving after 1 year and 43% surviving after 2 years. Results of chimeric antigen receptor-modified T-cell therapy at Memorial Sloan-Kettering Cancer Center in 16 patients with advanced adult acute B-lymphocytic leukemia (B-ALL) showed an overall complete remission rate of 88% for all patients, much higher than the complete response rate for remedial chemotherapy. The immune system is not only responsible for defense against microbial invasion, but also for the removal of altered host components from the body, and there exists an anti-tumor immune mechanism in the body. When the immune surveillance function is weakened due to the immune system itself or tumor cells, it provides favorable conditions for tumor development. The process of tumor cell recognition and killing by the immune system involves the production of specific antigens by tumor cells, the phagocytosis of apoptotic tumors by dendritic cells and the presentation of tumor antigens to T cells, and the recognition and killing of tumors by tumor-specific antigens by unsuppressed and activated T cells. The immunomodulatory T cells (Treg cells) regulate T cell activity by suppressing or disinhibiting T cells to avoid T cell killing of normal cells in the body. Tumor immunotherapy is to enhance the immune system’s ability to recognize and kill tumor cells in each of these steps.