In early triple-negative breast cancer, the presence of circulating tumor DNA (ctDNA) and circulating tumor cells after neoadjuvant chemotherapy may enable risk stratification of patients for disease recurrence and may predict outcomes, according to a preplanned correlative analysis of the phase II BRE12-158 trial, presented at the 2019 San Antonio Breast Cancer Symposium.^1,2

“Detection of ctDNA and circulating tumor cells in early-stage triple-negative breast cancer after neoadjuvant chemotherapy is an independent predictor of disease recurrence and represents an important novel stratification factor for future postneoadjuvant trials,” said Milan Radovich, PhD, of Indiana University School of Medicine, Indianapolis.

Milan Radovich, PhD

As Dr. Radovich explained, dying cells (normal and malignant) deposit DNA into the circulation; tumor DNA has unique genetic abnormalities that can suggest the presence of cancer. Circulating tumor cells also point to malignancy and can be isolated without detectable ctDNA. Their presence adds complementary information to ctDNA for detecting minimal residual disease, whereas their absence identifies a population not likely to relapse.

Two-thirds of patients with triple-negative breast cancer will not achieve a pathologic complete response after neoadjuvant chemotherapy. These patients will have residual disease at the time of surgery, will exhibit resistance to chemotherapy, and will likely have poor survival.

The presence of ctDNA and circulating tumor cells is known to herald minimal residual disease. An analysis of the recently completed phase II BRE12-158 trial expanded upon this information in determining whether ctDNA and circulating tumor cells can also predict recurrence in patients who are free of disease after standard therapy.

“Although it is important to have technology that can tell us which patients do poorly, I believe the more important thing now is to learn how to act” based on the results of such tests, Dr. Radovich said.

Study Details

Dr. Radovich, Bryan Schneider, MD, and their team analyzed plasma samples from 196 patients with early triple-negative breast cancer who underwent neoadjuvant chemotherapy and were found to have significant residual disease at the time of surgery. Tumors from these patients were genomically sequenced, and patients were randomly assigned to receive either genomically directed treatment or physician’s choice of treatment.

Bryan Schneider, MD

Plasma and circulating tumor cells were taken on day 1 of the first cycle or at the first routine visit for those randomly assigned to physician’s choice of therapy. In 142 patients, ctDNA was sequenced, and 63% were found to have mutated ctDNA (most commonly TP53). About 25% of patients tested positive for both ctDNA and circulating tumor cells, and 25% were double-negative.

Correlation With Survival

The primary endpoint of BRE12-158—2-year disease-free survival—is still maturing. Dr. Radovich reported on two other endpoints, based on 17 months of follow-up:

• Median distant disease–free survival: 32.5 months in ctDNA-positive patients; not reached in ctDNA-negative patients (hazard ratio [HR] = 2.99; P = .0055)
• 2-year distant disease–free survival: 56% vs 81%, respectively.

Additionally, in a multivariate analysis that controlled for clinical factors (residual cancer burden; nodal involvement; tumor size, grade, and stage; age; race), the detection of ctDNA was still independently associated with inferior distant disease–free survival. Overall, patients who tested positive for ctDNA were three times more likely to have distant disease recurrence than those who tested negative for ctDNA.

Additional Value of Circulating Tumor Cells

In the 112 patients with matched samples of ctDNA and circulating tumor cells, many patients tested positive for one marker and not another. In the evaluation of 29 patients whose disease recurred, the combined use of the two markers increased the predictive sensitivity of testing, from 79% with ctDNA alone to 90% when status of circulating tumor cells was added.

“Patients who tested negative for both had an exceptional superior outcome,” noted Dr. Radovich. “If they tested positive for one marker or the other, they had intermediate outcomes. And, if they tested positive for both ctDNA and circulating tumor cells, they had inferior outcomes.”

With ctDNA plus the status of circulating tumor cells, the following results were observed:

• Median distant disease–free survival: 32.5 months among patients who were double-positive but not reached among patients who were double-negative (HR = 5.29; P = .009)
• 2-year, distant, disease-free survival rates were 52% and 89%, respectively.

In patients who were double-positive, median disease-free survival was 20.8 months but not reached in double-negative patients (HR = 3.15; P = .04), although the date are immature.

Median overall survival was not reached in either group; 2-year survival rates were 51% and 76%, respectively (HR = 8.60; P = .007), although, again, the data are immature.

Positivity of circulating tumor cells alone (defined as at least one circulating tumor cell detected) showed a trend for an association with inferior outcomes but did not reach statistical significance. Increasing counts of circulating tumor cells, however, was significantly associated with inferior outcomes.

Future Trials

The next step in evaluating the utility of circulating tumor material is the umbrella-design, multiarm PERSEVERE trial (BRE18-334) of patients with early-stage triple-negative breast cancer and residual disease after neoadjuvant therapy. Patients with ctDNA-negative disease will automatically receive physician’s choice of therapy, whereas those with ctDNA-positive disease will undergo molecular testing and receive genomically directed or standard therapy.

The utility of ctDNA and circulating tumor cells is also being studied by other investigators in other cancer subtypes. The current study focused on triple-negative breast cancer, since this cancer typically recurs early, making it “the most opportune place to test this approach,” according to Dr. Radovich.

Testing of ctDNA and circulating tumor cells is not ready for routine clinical use, Dr. Radovich emphasized. “However, we do believe it’s ready for use in postneoadjuvant trials and should be incorporated as a posttreatment stratification factor in all future trials,” he added. Furthermore, serial sampling would increase the discriminatory capacity of these tests, according to Dr. Radovich, and may reveal “the dynamics of ctDNA while on treatment.” Serial sampling will, therefore, be part of the PERSEVERE trial.

Other Studies Find Value in Circulating Tumor Material

I-SPY2 investigators reported that personalized monitoring of ctDNA in high-risk patients undergoing neoadjuvant therapy reflected treatment response and risk of metastatic recurrence.³ Among 84 patients with high-risk, early breast cancer, early clearance of ctDNA during neoadjuvant therapy more than quadrupled the odds of achieving a pathologic complete response. Of patients experiencing distant recurrences, 90% had detectable ctDNA at some point during treatment. Clearance of ctDNA at any point in the study was significantly associated with improved outcomes.

“This is an exciting area,” said Laura Esserman, MD, Professor of Surgery and Radiology at the University of California, San Francisco. “It’s the future of how we will get patients to the best outcomes.”

Laura Esserman, MD

Serial sampling at 6-month intervals—for cell-free DNA (cfDNA) and circulating tumor cells—as well as testing for the expression of programmed cell death ligand 1 (PD-L1) on circulating tumor cells is currently part of a small study from Icahn School of Medicine at Mount Sinai, New York. It has enrolled 30 patients with early-stage triple-negative breast cancer (15 with sufficient sampling and sequencing). “Our study is somewhat unique because we are looking at a high-risk group from the time of diagnosis through initial treatment and into active surveillance,” said ­Hanna Irie, MD, PhD, of Mount Sinai who presented the poster.

Of six patients who did not achieve pathologic complete response after neoadjuvant treatment, three had pretreatment mutations in cfDNA/circulating tumor cells. “The list of mutations includes not only BRCA1/2, but a lot of other DNA-repair genes,” stated Dr. Irie. In contrast, of nine patients who did achieve pathologic complete response, three had such mutations. All patients found to have residual disease had at least one blood collection that revealed detectable cfDNA/circulating tumor cell mutations after treatment.

Hanna Irie, MD, PhD

Michael J. Donovan, PhD, MD

Of note, 80% of patients with residual disease were PD-L1–positive in tissue, and in one patient, PD-L1–positive circulating tumor cells were also detected. Co-investigator Michael J. Donovan, PhD, MD, said that detection of circulating tumor cell PD-L1 by a blood test would be a useful supplement to tissue staining, especially for patients lacking sufficient tissue PD-L1 staining. “Given the necessity for less invasive diagnostic approaches such as needle biopsies and fine-needle aspirates, we are using less tumor to make treatment decisions,” he noted. Sources of cellular and genetic material found in the blood will provide a valuable source of biologic data useful for understanding the dynamics of tumor response in the post-neoadjuvant setting.

In another study, Nicholas Turner, MD, of the Institute for Cancer Research in the United Kingdom, used ctDNA to genotype tumors for treatment selection.⁴ The plasmaMATCH trial evaluated 1,044 patients with breast cancer for ctDNA. Patients with these and other rare mutations were often effectively treated with matching targeted therapies, he reported.

Nicholas Turner, MD

Patients with HER2 mutations (2.7%) who received neratinib plus fulvestrant had a response rate of 25% and a median progression-free survival of 5.4 months. For patients with AKT1 mutations (4.2%), the AKT inhibitor capivasertib plus fulvestrant yielded a 22% response rate and a median progression-free survival of 10.2 months. 

DISCLOSURE: Dr. Radovich owns stock or other ownership interests in ArQule, Immunomedics, LifeOmic, MacroGenics, and Tyme Technologies; and has been reimbursed for travel, accommodations, or other expenses by LifeOmic. Drs. Esserman and Irie reported no conflicts of interest. Dr. Donovan has served as a consultant and advisor to LungLifeAI. Dr. Turner has served as a consultant or advisor to AstraZeneca, Bicycle Therapeutics, Bristol-Myers Squibb, Lilly, Merck Sharp & Dohme, Novartis, Pfizer, Repare Therapeutics, Roche, Taiho Pharmaceutical, and Zeno Pharmaceuticals; and has received institutional research funding from AstraZeneca, Bio-Rad Laboratories, Clovis Oncology, Guardant Health, Pfizer, and Roche.

REFERENCES

1. Yau C, van der Noordaa M, Wei J, et al: Residual cancer burden after neoadjuvant therapy and long-term survival outcomes in breast cancer: A multi-center pooled analysis. 2019 San Antonio Breast Cancer Symposium. Abstract GS5-01. Presented December 13, 2019.

2. Radovich M, Jiang G, Chitambar C, et al: Detection of circulating tumor DNA after neoadjuvant chemotherapy is significantly associated with disease recurrence in early-stage triple-negative breast cancer: Preplanned correlative results from clinical trial BRE12-158. 2019 San Antonio Breast Cancer Symposium. Abstract GS5-02. Presented December 13, 2019.

3. Magbanua MJM, Brown-Swigart L, Hirst G, et al: Personalized monitoring of circulating tumor DNA during neoadjuvant therapy in high-risk early stage breast cancer reflects response and risk of metastatic recurrence. 2019 San Antonio Breast Cancer Symposium. Abstract P5-01-04. Presented December 13, 2019.

4. Turner N, Kingston B, Kilburn L, et al: Results from the plasmaMATCH trial: A multiple parallel cohort, multi-centre clinical trial of circulating tumour DNA testing to direct targeted therapies in patients with advanced breast cancer (CRUK/15/010). 2019 San Antonio Breast Cancer Symposium. Abstract GS3-06. Presented December 12, 2019.