Developed from antigenic material procured from the tumor of the patient. Tumor cells are isolated from the tissue procured during biopsy or surgery. These cells are killed or attenuated and reinfused into the patient. Typically, to enhance immunogenicity, they are combined with an adjuvant, such as bacilli Calmette-Guerin (BCG) or C. parvum. A major problem with this approach is the work and cost associated with the production of vaccine for the individual patient. Also, some tumors escape the immune system because their antigens are not expressed on the tumor surface.