Abscopal effect

That radiation exposure of one part of the body can affect the carcinogenic risk of a distant part (abscopal effect) has not been shown in man, but the possibility of such an effect is suggested by the observation that sterilization of young women may protect against breast cancer, that is, pelvic irradiation sufficient to greatly diminish estrogen levels might have a similar effect. 

The so-called abscopal effect as a positive influence of treatment outside of the target area is not often observed after radiotherapy. 

Radiation-induced immune reaction or cytokines might affect tumors outside of the radiation field and under rare circumstances cause a significant outcome. Ohba et al. described a man who underwent radiation therapy for bone metastasis from hepatocellular carcinoma (Ohba etal. 1998). Surprisingly, regression of the non-irradiated primary tumor was observed. A rise in the serum tumor necrosis factor (TNF)-a after radiotherapy coincided with the response of the primary tumor and an immune response induced by TNF-a was suggested by the authors. Several cases of abscopal effects have been reported for leukemias and lymphomas after radiation therapy. One possible mechanism that is relevant mainly to leukemias and lymphomas is that the distant effect observed is due to the circulation of diseased lymphocytes through the field of local irradiation. 

To enhance the antitumor immunity, dendritic cell growth factor, Flt-3 ligand was combined with radiation therapy and there was greater induction of the abscopal effect compared with either treatment alone in certain tumor cell lines (Chakravarty etal. 1999 Demaria et al. 2004). Active variant of human macrophage inflammatory protein-la also induced abscopal effects by radiation in several mouse tumor models and the accumulation of CD8+ and CD4+ lymphocyte and NK cells was observed in non-irradiated tumor sites (Shiraishi et al. 2008). There have also been a number of studies that have shown that radiation combined with cytokine... 

The ahscopal effecL however, is not often observed, possibly because of the weak immune reaction. The majority of cancer antigens are the same as those expressed on normal tissues or are sUghtly modified mutants (Friedman 2002) and tumors can escape from the immune system. Because of this, cancer cells are often unable to activate naive T cells independently because they lack co-stimulatory molecules (Chen et aL 1992 Townsend and Allison 1993). To induce abscopal effects efficiently, the development of new methods to induce cancer-specific antigens by radiation appears necessary. 

Shiraishi K, Ishiwata Y, Nakagawa K, Yokochi S, Taruki C, Akuta T, et al (2008) Enhancement of antitumor radiation efficacy and consistent induction of the abscopal effect in mice by EC1301, an active variant of macrophage inflammatory protein-lalpha. Clin Cancer Res 14 1159-1166... 

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