[Sportschosun] A blood test may help predict the risk of cancer spread in patients with metastatic breast cancer, according to a new study.
The findings are expected to help identify patients with oligometastatic breast cancer, who may benefit from local treatments such as stereotactic radiotherapy.
A research team led by Professor Jee Suk Chang of Radiation Oncology and Professors Kim Min-hwan and Kim Geon-min of Medical Oncology at Yonsei Cancer Center said on the 17th that, after analyzing the progression patterns of metastatic breast cancer patients who received first-line systemic chemotherapy, the genomic instability score of circulating tumor DNA (ctDNA), or I-score, could serve as a benchmark for predicting whether the cancer will later spread to multiple sites.
The study was published in the latest issue of the International Journal of Radiation Oncology, Biology, Physics (IJROBP), a leading international journal in the field of radiation oncology.
Metastatic breast cancer refers to cancer that has spread beyond the breast to other organs, such as the bones, lungs, liver, or brain. Among these patients, those with a small number of metastatic lesions are drawing attention as candidates for direct treatment of the metastatic sites.
One representative local treatment is Stereotactic Body Radiation Therapy (SBRT), which delivers high-dose radiation precisely to the lesion. Because the radiation is concentrated on the target area, it can reduce damage to surrounding healthy tissue while eliminating metastatic lesions.
However, it has not been clear whether local treatment is effective for all patients with oligometastatic breast cancer. Breast cancer varies widely from patient to patient in subtype, rate of spread, and pattern of systemic progression, making it difficult to determine the right candidates based only on the number of lesions seen on imaging.
To address this issue, the research team focused on circulating tumor DNA (ctDNA), which is DNA shed by cancer cells and found in the blood. ctDNA consists of DNA fragments released into the bloodstream when cancer cells die or break down, allowing doctors to assess the genetic characteristics and changes of cancer through a blood test alone.
The team analyzed data from 207 metastatic breast cancer patients enrolled in a clinical study between 2017 and 2021. The results showed that even when the number of metastatic lesions was initially small, some patients later developed widespread metastases across multiple organs.
The five-year survival rate was 75.4% for patients with one to five metastatic lesions at diagnosis, 65.9% for those with six to 10 lesions, and 44.9% for those with more than 10 lesions. In other words, survival rates fell as the number of metastatic lesions increased.
In particular, patients with higher genomic instability in ctDNA faced a greater risk of rapid systemic spread. Genomic instability is an indicator of how unstable cancer cell DNA is and how much it changes.
The analysis found that patients with an I-score above 7.3 were about 3.2 times more likely to progress to widespread metastasis than those with lower scores. This trend remained even after adjusting for clinical factors such as age, cancer subtype, and the initial number of metastatic lesions.
Even if imaging shows only a small number of lesions and the cancer appears oligometastatic, high ctDNA instability suggests a strong possibility of rapid systemic spread, meaning treatment strategies should be adjusted accordingly. On the other hand, patients with low ctDNA instability may be good candidates for active local treatment such as stereotactic radiotherapy. Professor Jee Suk Chang said, "The reason the role of local treatment in oligometastatic breast cancer has remained controversial is that it has not fully reflected the molecular and biological characteristics that determine how the cancer progresses." He added, "This study suggests the possibility of using ctDNA to identify patients who are likely to benefit in practice."
Professor Kim Min-hwan stated, "In treating metastatic breast cancer, it is important to predict each patient's risk of systemic spread and combine drug therapy with local treatment accordingly." He added, "We will continue follow-up studies to further develop personalized treatment strategies based on ctDNA."
Jang Jong-ho, bellho@sportschosun.com
