Circulating tumor cell status may predict radiation benefit for breast cancer

By Robyn Boyle, RPh, for MDLinx
Published June 20, 2018

Key Takeaways

Researchers reported that early-stage breast cancer patients with at least one circulating tumor cell (CTC) who received radiotherapy (RT) had significantly longer survival outcomes than those who did not receive RT, according to a study published in JAMA Oncology. However, CTC-negative patients did not experience longer survival outcomes after RT.

The liquid component of solid tumors, called CTCs, indicates the presence of residual disease. They are detected in 10% to 30% of patients with nonmetastatic breast cancer. Although CTC status is prognostic for recurrence and death in breast cancer, currently there is no evidence to support using CTCs to predict response to therapy.

This study, led by Chelain R. Goodman, MD, PhD, Northwestern University Feinberg School of Medicine, Chicago, IL, used data from two large cohorts to determine whether CTC status is a predictive clinical marker of benefit of RT in early-stage breast cancer patients.

The cohort included patients with stages pT1 to pT2 and pN0 to pN1 breast cancer and known CTC status from the National Cancer Database (NCDB) and the German SUCCESS study, a prospective, multicenter, phase 3 clinical trial.

A total of 1,697 patients from the NCDB (16 men, 1,681 women; median age: 63 years) and 1,516 women from the SUCCESS clinical trial (median age: 52 years) were identified. CTCs were detected in 399 patients (23.5%) in the NCDB cohort and 294 (19.4%) in the SUCCESS cohort.

The primary outcomes included overall survival (OS), local recurrence-free survival (LRFS), and disease-free survival (DFS) after breast-conserving surgery.

The association of RT with survival was dependent on CTC status in both cohorts: the 4-year OS in the NCDB cohort (P < 0.001) and the 5-year DFS in the SUCCESS cohort (P=0.04).

In the NCDB cohort, RT was associated with longer OS in patients with CTCs (time ratio [TR]=2.04; P < 0.001), but not in patients without CTCs (TR=0.80; P=0.33). In the SUCCESS cohort, CTC-positive patients treated with RT exhibited longer LRFS (TR=2.73; P < 0.001), DFS (TR=3.03; P < 0.001), and OS (TR=1.83; P=0.003).

In a pooled analysis of patients from both cohorts who underwent breast-conserving surgery, RT was associated with longer OS in patients with CTCs (TR=4.37; P < 0.001) but not in patients without CTCs (TR=0.87; P=0.77). After mastectomy, RT was not associated with OS in CTC-positive or CTC-negative patients.

Moreover, there was no significant association of CTC status and 4-year OS with use of chemotherapy, hormone therapy, or tumor subtype.

The authors noted that although the NCDB database is large, the study was limited by the small proportion of patients within the NCDB who underwent evaluation for CTCs. Unknown biases may exist that were not considered. Furthermore, CTCs are heterogeneic and there is variability between and within patients, so undetermined genetic properties of CTCs might be responsible for their ability to predict survival.

“Treatment with RT was associated with longer LRFS, DFS, and OS in patients with early-stage breast cancer and detectable CTCs,” the authors concluded.

To read more about this study, click here.

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