In an earlier episode, we reviewed the principles of radiation therapy from a general perspective. This field of medicine unifies the management of cancer, by harnessing the therapeutic benefits of radiation, utilising ionising radiation. A specific form of this treatment is stereotactic radiotherapy, which administers radiotherapy from different angles around the body, with the focus of ionisation meeting at the targeted tumour to be treated. This allows the focussed delivery of high-dose radiation to the tumour, whilst nearby tissues receive a much lower and thus less damaging dose - lowering the risk of side effects. As a corollary to this treatment, a fascinating observation has arisen whereby localised radiation therapy may elicit an away from target tumour response — this is called “the Abscopal Effect”. Observed over 70 years ago in 1953 by RH Mole, who coined the term abscopal from Ab “away” and scopal “Target”, after observing a clinical response to irradiation at distant sites that were not directly exposed to radiation treatment. An abscopal response is defined as at least a 30% reduction in the size of the tumour from baseline, in any measurable non-irradiated lesion. In this episode, I was curious to learn more about this amazing event, which whilst still relatively rare, raises the perplexing question as to why the abscopal effect does not occur more frequently in patients receiving radiotherapy. To expand this conversation please welcome back Dr Marcus Foo - radiation oncologist with Genesis Care, who thoughtfully guides us through this subject. References: Dr Marcus Foo: www.genesiscare.com Mole RH. Whole body irradiation; radiobiology or medicine? Br J Radiol 1953;26:234-41. Formenti SC, Demaria S. Systemic effects of local radiotherapy. Lancet Oncol 2009;10:718-26. https://atm.amegroups.com › htmlRadiation therapy and the abscopal effect: a concept comes of age https://www.ncbi.nlm.nih.gov › pmcAbscopal effect of stereotactic radiotherapy combined with anti ... https://www.cancer.gov › def › stere...Definition of stereotactic radiation therapy - National Cancer Institute To be a guest on the show or provide some feedback, I’d love to hear from you: [email protected]. Dr Luke Crantock MBBS, FRACP, is a gastroenterologist in practice for over 25 years. He is the founder of The Centre for GI Health, based in Melbourne, Australia, and is passionate about educating General Practitioners and patients on disease prevention and how to manage and improve their digestive health.