medwireNews: The presence of circulating tumor cells (CTCs) could serve as a marker to identify patients with early-stage breast cancer who are likely to benefit from adjuvant radiotherapy, say researchers.
They caution, however, that the findings are “hypothesis generating,” but believe that “[a] prospective trial evaluating CTC-based management for [radiotherapy] in early-stage breast cancer merits consideration, with the ultimate goal of refining treatment recommendations to improve clinical outcomes, quality of life, and value of care.”
For the study, the team identified patients with stage pT1–pT2 and pN0–pN1 breast cancer who had undergone CTC testing from the National Cancer Database (NCDB; n=1697) and the German phase III SUCCESS trial (n=1516) investigating two chemotherapy regimens. Of these, a respective 23.5% and 19.4% tested positive for the presence of CTCs.
In the NCDB cohort, adjuvant radiotherapy was associated with a significantly better 4-year overall survival (OS) rate among patients who were positive for CTCs, at 94.9% versus 88.0% for those who did not receive radiotherapy, but not among those lacking CTCs, with corresponding rates of 93.9% and 93.4%, respectively.
Similarly, the 5-year disease-free survival rate in the SUCCESS cohort was significantly higher with versus without radiotherapy for patients who tested positive for CTCs, at 88.0% versus 75.2%, but not those who tested negative, at 92.3% versus 88.3%.
Of note, a pooled analysis showed that the dependence on CTC status of the association between radiotherapy and survival was restricted to patients who underwent breast-conserving surgery. Specifically, among patients positive for CTCs, the 5-year OS was 87.2% for radiotherapy-treated patients and 73.3% for those not given radiotherapy, while the rates were a comparable 95.5% and 92.7%, respectively, for CTC-negative participants.
No such significant interaction between CTC status, radiotherapy, and OS was observed for patients who had a mastectomy, say Chelain Goodman (Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA) and team in JAMA Oncology.
Commentators Corey Speers (University of Michigan Cancer Center, Ann Arbor, USA) and Hope Rugo (University of California, San Francisco, USA) describe the results as “provocative.” However, they point out that “[n]either the NCDB nor the SUCCESS trial was designed to test or answer radiation therapy questions, and therefore both data sets likely have confounding factors that affect decisions to deliver radiation therapy to individual patients.”
These data “should therefore not be taken to mean that women without CTCs do not benefit from radiation therapy,” the commentary authors continue.
Speers and Rugo say that before such biomarkers can be translated to the clinic, “we need further evidence of accuracy, reproducibility, and efficacy in prospectively designed trials.”
And they conclude: “The ongoing development of potential biomarkers to individualize radiation therapy holds promise as we seek to finally realize personalized medicine as it relates to radiation therapy for women with early-stage breast cancer.”
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