Abscopal effect

The abscopal effect is a phenomenon in the treatment of metastatic cancer where localized irradiation of a tumor causes, not only a shrinking of the irradiated tumor, but also a shrinking of tumors far from the irradiated area. While this phenomenon is extremely rare, its effect on the cancer can be stunning, leading to the disappearance of malignant growths throughout the entire body. Such success has been described for a variety of cancers, including melanoma, lymphoma, and kidney cancer.

Scientists are not certain how the abscopal effect works to eliminate cancer in patients. Studies in mice suggest that the effect may depend upon activation of the immune system. In a case study reported at Memorial Sloan-Kettering Cancer Center in New York City, changes in a metastatic melanoma patient’s immune system were measured over the course of treatment. The team observed changes in tumor-directed antibody levels and immune cell populations that occurred at the time of the abscopal effect. These findings support the idea that radiation may help stimulate the immune system to fight cancer. At this time, T-cells and dendritic cells are believed to play a primary role.