Chromosomal Instability: A Potential Biomarker of Radiation Response.

Radiotherapy is a widely used cancer treatment modality with more than 70% of head and neck cancer (HNC) patients receiving it in either the definitive or adjuvant settings. Currently, all HNC patients, regardless of human papillomavirus (HPV) status, are treated with the same radiation dose, yet treatment response remains highly variable across patients and radiation-induced treatment toxicities continue to pose significant clinical challenges. To date, there are no clinically approved methods or biomarkers that can predict patient response to radiation, hindering the development of personalized radiation treatment strategies. In our recent publication in the International Journal of Radiation Oncology, Biology, Physics (1), we approached this clinical problem by focusing on a biological characteristic occurring in nearly all cancer cells to different degrees; chromosomal instability (CIN). CIN is defined as an ongoing rate of chromosome missegregation events over consecutive cell divisions, and is a type of genomic instability, which is a hallmark of cancer. One consequence of CIN is aneuploidy, or a state of abnormal chromosome content. It is important to distinguish CIN from aneuploidy as we discovered it is the rate of chromosome missegregation during mitosis (CIN) that determines cell fate after radiation.