Radiation-associated Tumors in the Central Nervous System and the Head and Neck: What Radiologists Should Know

Therapeutic advances in the treatment of malignant neoplasms, including tumors that affect the central nervous system and the head and neck areas, have improved their prognosis. Radiation therapy plays an important role as an effective therapeutic technique for malignant neoplasms. However, secondary tumors associated with radiation therapy are increasingly recognized as a delayed complication. Although the incidence of these secondary tumors is relatively rare (approximately 1%), the morbidity and mortality rates are high. Therefore, radiologists should be aware of these long-term consequences of antineoplastic therapy to facilitate appropriate observations and a correct diagnosis, and avoid adverse outcomes. In general, a radiation-associated tumor occurs in the irradiated area of a patient after a relatively long latency. Radiation-associated tumors occur in patients without a history of tumor-predisposition syndrome, and the histology of radiation-associated tumors is different from the primary tumor. Imaging plays an important role in detection, staging, pretherapy planning, and follow-up of radiation-associated tumors. Unfortunately, the imaging characteristics of radiation-associated tumors are similar to those of primary tumors. However, some clinical characteristics may be useful for differentiating from other treatment-related changes or primary tumor recurrence. This review article provides a comprehensive overview of clinical and imaging characteristics of various types of radiation-associated tumors.

Learning Objective: Recognize the general features of radiation-associated tumors, clinical characteristics, and imaging appearances of various types of radiation-associated tumors, and present differentiating features from non-neoplastic radiation-associated conditions that mimic radiation-associated tumors.