The tumor microenvironment is a complex assortment of cells that includes a 
variety of leukocytes. The overall effect of the microenvironment is to support 
the growth of tumors and suppress immune responses. Immunotherapy is a highly 
promising form of cancer treatment, but its efficacy can be severely compromised 
by an immunosuppressive tumor microenvironment. Chemotherapy and radiation 
treatment can mediate tumor reduction through cytotoxic effects, but it is 
becoming increasingly clear that these forms of treatment can be used to modify 
the tumor microenvironment to liberate tumor antigens and decrease 
immunosuppression. Chemotherapy and radiotherapy can be used to modulate the 
tumor microenvironment to enhance immunotherapy.