He noted that further study is needed to determine how these findings could affect clinical practice. “If we have a negative CTC assay, can we really effectively spare continuing extended adjuvant endocrine therapy beyond 5 to 7 years? Secondly, what do we do for those patients who have a positive assay. We know that they have a higher recurrence rate, what can we do to prevent it?” Sparano also mentioned that new therapeutic strategies, such as oral selective ER downregulators and CDK4/6 inhibitors, should be investigated in clinical trials to see if they could prevent recurrence for patients with positive CTCs.
He noted that investigators plan to look next at differences between the patients with positive CTC results who had a recurrence and those who did not. “There’s probably a second hit or a change in the microenvironment that are driving these patients to have a recurrence, and for others to not have a recurrence despite the presence of circulating tumor cells,” Sparano said. Additionally, they are also planning a trial that will look at serial CTC assays in this patient population to investigate the impact of CTC burden over time.
- Sparano JA, O’Neill A, Alpaugh K, et al. Circulating tumor cells and late recurrence of breast cancer. Presented at: 2017 San Antonio Breast Cancer Symposium; December 5-9, 2017; San Antonio, TX. Abstract GS6-03. abstracts2view.com/sabcs/view.php?nu=SABCS17L_1464&terms=.
- Pan H, Gray R, Braybrooke J, Davies C, et al; for the EBCTCG. 20-year risks of breast-cancer recurrence after stopping endocrine therapy at 5 years. N Engl J Med. 2017;377(19):1836-1846. doi: 10.1056/NEJMoa1701830.