CHICAGO -- Circulating tumor DNA successfully identified minimal residual disease in patients with hormone receptor-positive (HR+) breast cancer who are at high risk for recurrence – generally years before metastases occurs. The findings come from the CHiRP study, which included patients who were at least 5 years post diagnosis.
The researchers and other groups previously showed that minimal residual disease (MRD) status is associated with distant-recurrence free survival, “yet little is known about ctDNA in the late adjuvant setting in hormone receptor-positive breast cancer,” said Marla Lipsyc-Sharf, MD, a clinical fellow in medicine at Dana-Farber Cancer Institute, Boston. Dr. Lipsyc-Sharf presented her findings June 4 in Chicago at the annual meeting of the American Society of Clinical Oncology.
The study was simultaneously published online in the Journal of Clinical Oncology.
Plasma samples were collected at follow-up visits every 6-12 months, and a personalized version of the RaDaR assay was used to detect ctDNA associated with MRD. Although the technology is currently only useful for research, the team hopes it can soon provide clinical guidance. “The CHiRP study is an important first step toward an understanding of the baseline prevalence and role of ctDNA in this setting. Multiple prospective clinical trials are underway or beginning to establish the clinical utility of ctDNA assays in this setting and understand whether intervention after MRD detection improves patient outcomes, such as survival or quality of life,” she said.
Ben Ho Park, MD, PhD, an oncologist with Vanderbilt University Medical Center, Nashville, Tenn., described the findings as encouraging.
“I think most of us saw this very striking data that you could actually predict who’s going to recur and that all patients who did recur were ctDNA positive. The numbers are really, indeed very encouraging that we can develop assays now that detect minimal residual disease with serum monitoring. It really opens up the floodgates for designing studies [to determine] who to treat with additional adjuvant therapies while they’re still in the adjuvant phase of breast cancer therapy,” Dr. Park said during a discussion that followed the presentation.
The study included 83 patients with high-risk HR+ breast cancer and no evidence of recurrence within 5 years of diagnosis. High risk was defined as T3/T4 and/or N2/N3 disease; T1/N1 disease with 3 or more lymph nodes involved; or T2N1 disease with Ki67 ≥ 20%, grade 3, or oncotype DX score ≥ 26.
For each patient, clinicians designed a tumor-informed liquid biopsy assay to detect plasma ctDNA. A total of 68.7% of participants had stage 3 disease. A total of 90.4% received curative-intent chemotherapy, and all received endocrine therapy. A total of 47% remained on endocrine therapy at their last follow-up.
A total of 93.2% of patients who completed adjuvant endocrine therapy had at least 5 years of treatment. A median of 8.4 years elapsed between diagnosis and first ctDNA sample, and the median follow-up was 10.4 years from diagnosis and 1.8 years from the first sample.
A total of 5% of patients had MRD when they entered the study, and 10% were found to have MRD at any time. Of 6 patients (7.2%) who experienced a metastatic recurrence, all were MRD+, and ctDNA evidence appeared as soon as 37.6 months before diagnosis (median 12.4 months). Of eight patients who were MRD+ at some point, two of them had not had a recurrence at the latest follow-up, and one patient had no follow-up at all, and the other had a follow-up 15.4 months after ctDNA detection.
Limitations of the study included a limited follow-up period and low rate of recurrence, as well as infrequent plasma sampling.
Dr. Lipsyc-Sharf has no relevant financial disclosures. Dr. Park has financial relationships and/or has received funding from Celcuity, Loxo, Casdin Capital, EQRx, Guardant Health, Hologic, Horizon Discovery, Jackson Laboratory for Genomic Medicine, Sermonix Pharmaceuticals, Abbvie, GE Healthcare, Lilly, Pfizer, Horizon Discovery, and Tempus.