ctDNA testing is currently being studied to monitor patients who have been diagnosed with breast cancer. Small retrospective studies have shown that detection of ctDNA in plasma, after patients have completed therapy for early-stage breast cancer, is associated with a very high risk of relapse. 17
Ongoing studies are examining the tailoring of adjuvant treatment based on ctDNA. If these trials are successful, certain aspects of adjuvant treatment could be lessened, or omitted, for patients who have undetectable ctDNA or intensified for patients who have detectable ctDNA after definitive treatments. This could personalize treatment specifically to the patient.
The detection and persistence of ctDNA in the middle of neoadjuvant systemic therapy may have the potential to negatively predict response to treatment and identify patients who will not achieve pathologic complete response. This may have the potential to aid in clinical decision-making for treatment escalation in these nonresponders. 18
Despite these distinct characteristics, the low levels of ctDNA found in early-stage disease, along with the lack of ctDNA shedding from some tumors, can further complicate or impede detection of recurrence in early-stage breast cancer. Testing is further complicated by hematologic genetic alterations. 5 The limitation of ctDNA approaches is that these techniques only detect known mutations in certain genes, so patients without these mutations could be overlooked, limiting the application of this technology. 19
Overall, ctDNA testing represents a promising area of research for the diagnosis, treatment, and monitoring of breast cancer. While more research is needed to fully understand its potential, the advances in this technology are certainly exciting and could lead to significant improvements in patient outcomes. It is hopeful that in the near future, ctDNA testing from liquid biopsy could become a standard of care in breast cancer screening, ultimately helping clinicians to personalize treatment therapies and improve patient outcomes when treating patients with breast cancer.