A Case Report on Metastatic Thyroid Carcinoma: Radiation-induced Bystander or Abscopal Effect?

The effects of radiation on human tissues are not just local as once believed but they can appear even outside of the irradiated field [1-5]. Based on what has been published, both from in vitro and in vivo studies [6,7], it is known that those effects are at least regional. The irradiated tumor tissue may communicate, in some way, radiation effects to the not irradiated neighboring or distant tumor. If the irradiated tumor is forming a physical contact with a not irradiated tumor, then the phenomenon of transmission of the radiation damage is called “bystander effect”. The “abscopal effect” [8], on the other hand, refers to the phenomenon of damage communication between irradiated tumor and a distant tumor that has not been irradiated. The first report on abscopal effect dating from 1953 was published by Mole [1]. Thereafter many authors have published observations on in vivo abscopal effects in different tumor types, such as malignant melanoma [2], lymphoma [3], hepatocellular carcinoma [4], and cervical carcinoma [5]. So far no authors have published on such phenomena induced by thyroid carcinoma. This is the first case report on a radiation-induced abscopal effect in a thyroid cancer-patient.