Promise of ctDNA liquid biopsy grows but high costs hinder access in Korea

A report confirms the usefulness of liquid biopsy using circulating tumor DNA (ctDNA), raising the possibility of its application in Korean clinical practice.

On Tuesday, the Korea Cancer Study Group (KCSG) held a news conference at the Korea Press Center to discuss the significant clinical results of the 2025 American Society of Clinical Oncology Annual Meeting (ASCO 2025) and the latest trends in cancer research. The topic was “ASCO 2025 Review with KCSG: A Review of Research.”

ctDNA is a tumor-derived DNA fragment, a next-generation sequencing (NGS)-based molecular diagnostic technology that can analyze cancer genetic information using only blood, providing an alternative for patients with difficulty obtaining tissue. Liquid biopsies can be used not only to diagnose cancer but also to monitor drug response and patient prognosis by obtaining tumor information using only blood tests.

At ASCO 2025, many studies demonstrated that ctDNA can be used as a key tool to determine treatment strategies rather than just as a biomarker to predict the prognosis of cancer patients.

In particular, a study of colorectal cancer patients (Oral Abstract #3503) was highlighted as the first randomized clinical trial to use postoperative ctDNA to identify minimal residual disease (MRD) to adjust the need for and intensity of adjuvant therapy.

The SERENA-6 study of breast cancer patients, also presented in the keynote, showed that ctDNA significantly improved progression-free survival (PFS) by identifying treatment responses faster than traditional imaging tests and adjusting drug therapy earlier. The study used ctDNA to detect ESR1 mutations every two to three months and imaging to assess disease response and progression.

“For metastatic cancer, ctDNA allows for real-time monitoring,” said Professor Park In-keun of the Department of Medical Oncology at Asan Medical Center. When anticancer drugs are used as adjuvant therapy before surgery, ctDNA tests can be used to examine drug response, and in MRD solid cancers, treatment can be intensified, or tests can be refined depending on whether ctDNA is expressed or not."

He said liquid biopsy techniques that use ctDNA as a biomarker have proven useful and are already being applied clinically in the U.S.

"It is expected that ctDNA will be used mainly in patients with bone metastases that are difficult to biopsy or at risk of recurrence after surgery. Research on colorectal cancer is being actively conducted and will likely be reflected in future guidelines. We know that in the United States, colorectal cancer surgery patients are tested for ctDNA."

However, it has been pointed out that NGS is not covered in Korea for most cancers, so the cost of the test alone exceeds 1.5-3 million won ($1,090 to $2,180). The detection rate of ctDNA varies depending on the cancer type and stage, so its introduction is limited to domestic clinical practice.

"Unlike only looking at the expression of fragmentary genes, such as EGFR in lung cancer and PIK3 in breast cancer, looking at MRD in colorectal and bladder cancers has a cost issue because it requires repeated testing," said Professor Ahn Jin-seok of the Department of Hematology and Oncology at Samsung Medical Center, who also heads the KCSG.

"If you look at the SERENA-6 study (in breast cancer), there is a cost issue because you have to test ctDNA repeatedly. This is an area that requires social consensus. It remains to be seen whether the drug (in the trial) can be introduced into the country, as well as the repeated testing of ctDNA," Ahn added.

With the release of clinical data for talatamab, which could be a bispecific T-cell engager antibody (BiTE), at ASCO 2025, the prospect of new modalities utilizing liquid biopsy may be around the corner.

The DeLLphi-304 study, presented at ASCO 2025, showed that talatamab, a member of the BiTE family of drugs that simultaneously targets DLL3 and CD3, significantly improved overall survival (OS) in patients with small cell lung cancer (13.6 months for talatamab vs. 8.3 months for control), outperforming existing therapies. These results suggest that talatamab can become the new standard of care for small cell lung cancer (SCLC).

The KCSG also highlighted clinical study announcements that expanded the use of CAR-T therapies from hematologic cancers to solid tumors.

The CT041-ST-01 study, which used satricaptagene autoleucel, a CAR-T cell therapy targeting the Claudin (CLDN) 18.2 protein, found that it significantly prolonged progression-free survival in patients with gastric and gastroesophageal junction cancers. This is considered significant evidence that CAR-T has reached the stage of clinical applicability in solid tumors.

"In the past, it took many years for a new drug to become a standard of care, but the pace of change is accelerating to the point where it can be reflected in guidelines within two to three years," Professor Park said. "At ASCO 2025, we saw that innovative new drugs have moved beyond the research stage and have reached the stage where they can be applied in clinical practice."

Meanwhile, 255 presentations, including oral and poster presentations by Korean researchers, were made at ASCO 2025 this year. Of these, 60 studies were presented by members of the KCSG as first authors or presenters, reaffirming the status of Korean cancer clinical research.

Four KCSG-led clinical trials were presented, including oral presentations by Professor Sohn Joo-hyuk of Yonsei Cancer Hospital and Professor Park Kyong-hwa of Korea University Anam Hospital, and poster presentations by Professor Cha Yong-jun of the National Cancer Center and Professors Kim Beom-seok and Kim Mi-so of Seoul National University Hospital.