Circulating Tumor Cells Predictive of Adjuvant Radiotherapy Benefit in Early Breast Cancer

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Researchers determined that there was a significant association between overall survival and adjuvant RT when factoring in CTC status.
Researchers determined that there was a significant association between overall survival and adjuvant RT when factoring in CTC status.

Radiotherapy (RT) may improve survival outcomes among patients with early-stage breast cancer and detectable circulating tumor cells (CTC), according to a study published in JAMA Oncology.1

Although the presence of CTCs has been established as a prognostic factor for various measures of survival, its value for guiding clinical interventions is not yet fully understood. Researchers hypothesized that CTCs may identify patients who would benefit from adjuvant radiotherapy.

For this cohort study, researchers collected outcomes data of 1697 women with early-stage breast cancer from the National Cancer Database (NCDB) and 1516 women from the phase 3 SUCCESS clinical study. Overall, 399 (23.5%) and 294 (19.4%) patients from the NCDB and SUCCESS study had positive CTC statuses, respectively.

Results showed that there was a significant association between overall survival (OS) and adjuvant RT when factoring in CTC status.

In the NCDB cohort, the 4-year OS rate was 94.9% among CTC-positive patients who received RT compared with 88.0% among CTC-positive patients who did not and was 93.9% and 93.4% among CTC-negative patients that received RT and did not, respectively (P < .001). Patients in the SUCCESS cohort had improved 5-year disease-free survival (DFS) if they had CTC-positive RT (88.0%) compared with CTC-positive non-RT (75.2%), and 5-year DFS was 92.3% for CTC-negative RT and 88.3% for CTC-negative non-RT (P = .04).

RT was associated with longer OS among patients who were CTC-positive (P < .001) but not with those who were CTC-negative (P = .33) in the NCDB cohort, and also was found to prolong local-recurrence free survival (P < .001), DFS (P < .001), and OS (P = .003) among CTC-positive patients compared with patients who were CTC-negative.

Further analysis revealed that RT prolonged OS among patients from both cohorts who underwent breast-conserving surgery if they had positive-CTCs (P < .001) but not among patients without CTCs (P = .77); no OS benefit was observed with RT among patients post-mastectomy regardless of CTC status.

The findings of this study strongly suggest that CTC status may be predictive of RT benefit among patients with early breast cancer. The authors concluded that “A prospective trial evaluating CTC-based management for RT 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.”

Reference

  1. Goodman CR, Seagle BL, Friedl TWP, et al. Association of circulating tumor cell status with benefit of radiotherapy and survival in early-stage breast cancer [published online May 3, 2018]. JAMA Oncol. doi: 10.1001/jamaoncol.2018.0163

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