The Use of ctDNA MRD Precision Medicine Surveillance After Definitive Treatment of Early-Stage, High-Risk Breast Cancer in a Radiation Oncology Practice: A Case Series

Standard of care for patients with early-stage breast cancer typically does not use systemic surveillance or imaging studies following the administration of definitive treatment. However, the use of a circulating tumor DNA (ctDNA) test may provide an opportunity for early detection of cancer recurrence, particularly in patients with high-risk or aggressive forms of the disease. We present two cases of early-stage triple-negative breast cancer (TNBC) in which ctDNA screening facilitated early detection of recurrence prior to detection by imaging. As a result, treatment was initiated sooner than would have been possible in the absence of ctDNA screening. These cases underscore the potential utility of ctDNA screening integration within a radiation oncology practice for the detection of recurrent breast cancer, and how their use in routine clinical practice could benefit patients. We also provide a review of the current literature on ctDNA testing, including its benefits and limitations. While there is currently insufficient data to support the routine use of ctDNA screening in all patients, we speculate on specific patient populations that may derive the greatest benefit from this innovative diagnostic tool.