Tumor induction by chemotherapy

Without chemotherapy, the fi ve-year survival rate of detected cancers would be between 0 and 15%, depending on the tumor, and between 17 and 85% with current therapy. Several warnings call attention to the dangers of chemotherapy-induced side effects, most notably the potential for tumor-inducing ability, which can affect 5-10% of patients who have recovered beyond fi ve years. Some systematically applied drugs used in chemotherapy (alkylating agents, etoposide, arsenic trioxide) are able to cause mutations in healthy cells of the patients, increasing the likelihood that the mutated cells will start a later (secondary) tumor formation. In addition to mutagenic effects, some chemotherapeutic agents exert their effects on normal myeloid and epithelial cells of the body, which, by altering the tissue microenvironment, create the potential for malignant transformation. Tumor-associated macrophages (TAMs), which can alter gene expression patterns by tumor cell secreted factors and promote the survival and invasiveness of tumor cells by pro-carcinogenic signals, are very important in this process. It is of utmost importance that doctors, pharmacists, technicians and nurses working with cancer-causing materials do not come into direct contact with dangerous substances and wear appropriate protective equipment.