ctDNA Provides Prognostic and Predictive Value in Early-Stage Breast Cancer

Circulating tumor DNA (ctDNA) can be used as a predictive measure of response to neoadjuvant chemotherapy and inform overall prognosis in patients with early-stage breast cancer, providing information that can be used to tailor treatment, according to results of a prospective study published in the Journal of Clinical Oncology Precision Oncology.

Findings showed that the level of ctDNA after 2 cycles of neoadjuvant chemotherapy was predictive of local response after all cycles of therapy (area under the curve [AUC], 0.81; 95% CI, 0.61-1.00). Additionally, serial ctDNA assessment during treatment was complementary to imaging as a method to predict response to neoadjuvant chemotherapy.

The results also demonstrated that positive baseline ctDNA was associated with a significantly worse disease-free survival (DFS; HR, 5.72; 95% CI, 1.74-18.81; P = .011) and overall survival (OS; HR, 11.27; 95% CI, 2.99-42.45; P = .004) in patients with early-stage breast cancer, particularly in those with estrogen receptor (ER)—negative disease.

“These data together indicate that the presence of ctDNA before neoadjuvant chemotherapy is a marker of poor prognosis that helps physicians to distinguish the patients with high risk of metastasis from those with low risk,” Shunying Li, PhD, of Sun Yat-sen University, and coinvestigators wrote.

Fifty-two patients with early-stage breast cancer who underwent neoadjuvant chemotherapy were enrolled in the trial. Eight patients were excluded from further study because of insufficient cell-free DNA (cfDNA) at baseline. Serial plasma samples were taken before, during, and after treatment and analyzed alongside tumor biopsies that were assessed with next-generation sequencing (NGS) at baseline.

The clinical utility of the presence and changes in ctDNA to predict tumor response and prognosis in patients treated with neoadjuvant chemotherapy served as the study’s primary endpoint.

All patients received 3 to 8 cycles of anthracycline/taxane-based neoadjuvant chemotherapy. Most patients were ≥T2 or had lymph node involvement.

Through NGS, positive baseline ctDNA was identified in 21 of 44 patients with early-stage breast cancer. Most patients with positive ctDNA had ≥1 mutation (range, 1-8) in their primary tumor. TP53 (n = 15), PIK3CA (n = 5), GAB2 (n = 3), and IRS2 (n = 3) were the most commonly mutated genes found in plasma.

Baseline ctDNA positivity did not have a significant correlation with tumor size, lymph node status, ERBB2 status, and Ki-67 status. However, tumors with positive ctDNA were more likely to be ER-negative or progesterone receptor—negative (P <.05). Additionally, higher levels of ctDNA at baseline were significantly associated with larger tumor size, ER-negativity, and triple-negative breast cancer.

Investigators reported complete responses (n = 3), partial responses (PRs; n = 24), stable disease (n = 16), and progressive disease (n = 1) in patients, according to RECIST v1.1 criteria. At a median follow-up of 46 months (range, 11-68), 11 patients had distant metastasis and 9 had died of metastatic disease.

The objective response rate (ORR) after treatment was higher in ctDNA-negative patients versus ctDNA-positive patients, at 73.9% versus 47.6%, respectively. This difference, though not statistically significant (P = .13), might have been due to the limited population size, Li and coinvestigators wrote.

Patients who responded to neoadjuvant chemotherapy had lower levels of ctDNA than patients who did not, with a significant difference after the second cycle of therapy (P = .03) and after all cycles of therapy (P = .02), with the exception of no statistically significant difference after cycle 1 (P = .290).

Due to the current limitations of ultrasound or magnetic resonance imaging in monitoring response to neoadjuvant chemotherapy in practice, investigators collected plasma samples from patients with positive ctDNA during treatment and compared them with baseline samples.

One patient was not included in the analysis due to insufficient cfDNA during treatment. Among the 20 evaluable patients, the ORR was 45% (n = 9) with imaging. Notably, 1 patient who had a PR on imaging had rising ctDNA during treatment and following surgery. At 21 months of follow-up, the patient had multiple distant metastases and died 46 months after surgery.

“The increase of ctDNA in this case indicated the early micrometastases undetected by imaging did not respond to neoadjuvant chemotherapy well, although the primary tumor did, suggesting that ctDNA is better than imaging of local tumor to monitor the overall response to neoadjuvant chemotherapy,” Li and coinvestigators wrote.

Moreover, the amount of ctDNA before surgery (AUC, 0.82; 95% CI, 0.64-1.00) also demonstrated higher predictive value compared with ultrasound after 2 cycles of therapy (AUC, 0.76; 95% CI, 0.58-0.94), though not statistically significant.

Regarding prognosis, inferior DFS (HR, 5.11; 95% CI, 1.08-24.18; P = .04) and OS (HR, 5.46; 95% CI, 1.14-26.10; P = .033) were largely impacted by ER-negative patients with positive ctDNA. The DFS and OS rate was 100% in ER-negative patients with negative baseline ctDNA versus 36% in patients with positive baseline ctDNA.

There was no significant difference in DFS (HR, 1.75; 95% CI, 0.23-13.39; P = .57) or OS (HR, 1.66; 95% CI, 0.095-28.94; P = .72) in ER-positive patients with positive or negative baseline ctDNA.

Among the 20 patients with positive ctDNA at baseline, 6 developed negative ctDNA and 14 continued to have positive ctDNA prior to surgery. The relapse rate was 50% among patients with persistent ctDNA and 33% among those with negative ctDNA prior to surgery. The relapse rate was magnified among patients with ER-negativity. Though, the sample size prevented the authors from declaring statistical significance.

“Our study demonstrates the feasibility and validity of ctDNA in patients with early breast cancer receiving neoadjuvant chemotherapy,” Li and coinvestigators concluded. “Serial tracking of ctDNA has significant potential to complement imaging-based tumor assessment during neoadjuvant chemotherapy in early breast cancer. ctDNA analysis may help to identify high-risk patients for escalating the treatment.”

Li S, Lai H, Liu J, et al. Circulating tumor DNA predicts the response and prognosis in patients with early breast cancer receiving neoadjuvant chemotherapy. JCO Precision Oncol. 2020;4:244-257. doi: 10.1200/PO.19.00292