On Sept. 19, 2002, a new approach to cancer treatment that replaced a patient’s immune system with cancer-fighting cells can lead to tumor shrinkage. National Cancer Institute researchers demonstrated that immune cells, activated in the laboratory against patients’ tumors and then administered to those patients, could attack cancer cells in the body. The experimental technique, known as adoptive transfer, had shown promising results in patients with metastatic melanoma who have not responded to standard treatment.