E4559. Radiation-Induced Sarcoma: Breast Edition
  1. Neal Shah; Vanderbilt University Medical Center
  2. Tamarya Hoyt; Vanderbilt University Medical Center
Radiation therapy has become an essential component of the treatment of many subtypes of breast cancer. A well-known but rare side effect of ionizing radiation is the development of a radiation induced sarcomas (RIS). A rare iatrogenic malignancy, with an overall reported occurrence rate of 0.03-0.2% at 10 years, RIS can be extremely difficult to detect. Ultimately, diagnosis depends on a multimodality and multidisciplinary approach for both diagnosis and treatment. As worldwide incidence rates of breast cancer continue to increase (possibly secondary to increasing adaptation of westernized cultures of under-developed countries and increasing detection rates) treatment rates and survival rates also continue to increase. With a median reported latency period of 14 years, RIS incidence rates will also continue to increase, making diagnosis and understanding of these rare tumors increasingly crucial.

Educational Goals / Teaching Points
Through use of several case studies and review of their pertinent imaging findings (including ultrasound, mammograms, CT, PET scans, MRI) as well as a brief discussion of the stochastic effects of radiation therapy, this exhibit aims to shed light on a rare iatrogenic entity that is becoming an increasingly important and common topic as breast cancer incidence and treatment rates continue to rise. Biopsy-proven diagnoses will be discussed in correlation with multimodal imaging findings. Pertinent history will provide diagnostic clues in cases and interesting statistical facts will be included.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Both histologic and imaging findings of RIS tend to vary from tissue to tissue and are often not pathognomonic in their features making detection even harder. Furthermore, differences between RIS and sporadic-type sarcomas are not well understood. In consideration of breast cancer and posttherapy changes (excision and radiation therapy) altered tissue anatomy in the form of tissue scar, reconstruction, and other expected postsurgical changes also contribute to increasing difficulty in the recognition of early changes. Thus, imaging can often result in false-negative outcomes. Although these tumors do vary widely in their appearance, onset, and presentation, there are a few shared characteristics that should be considered in follow-up and surveillance imaging. Furthermore, depending on area of interest, specific modalities have been shown to be more helpful than others, specifically CT vs MR. This presentation will also aid in management discussion. Though detection will continue to rely on a multimodality approach, as depicted through featured cases, diagnosis may largely depend on physical examination findings and patient history.

RIS, a rare entity, is still poorly understood. With increasing incidence and treatment rates of breast cancer, the prevalence of RIS will only increase. This exhibit aims to shed light on the imaging characteristics of RIS following breast cancer treatment through the use of several case studies. Goals will be to further understanding and help characterize some of the posttreatment changes that can be more specific to diagnosis.