Monitoring ctDNA can personalize the use of consolidation immunotherapy in patients with LS-SCLC

A new study presented at the International Association for the Study of Lung Cancer 2025 World Conference on Lung Cancer (WCLC) demonstrates that monitoring circulating tumor DNA (ctDNA) can refine and personalize the use of consolidation immunotherapy in patients with limited-stage small cell lung cancer (LS-SCLC).

The research, led by scientists at the National Cancer Center of China, assessed ctDNA in 177 patients with LS-SCLC treated with chemoradiotherapy (CCRT), 77 of whom received consolidation immune checkpoint inhibitors (ICIs). Circulating tumor DNA was measured at multiple time points to evaluate its ability to predict survival outcomes and immunotherapy benefits.

This is the first study to show that early ctDNA detection after induction chemotherapy can help identify patients who are more likely to benefit from consolidation immunotherapy. It's a step toward precision immunotherapy in limited-stage SCLC."

Dr. Nan Bi, from the Chinese Academy of Medical Sciences

Key findings:

• Consolidation ICI improved overall survival vs. CCRT alone (HR: 0.41; p = 0.031).
• Patients who were ctDNA-positive at post-induction had significantly better PFS and OS with ICI compared to CCRT alone.
• ctDNA-negative patients did not show added benefit from ICI.
• Maintaining ctDNA negativity during immunotherapy was associated with better prognosis.
• ctDNA at post-induction (t1) was more predictive of treatment response than ctDNA post-radiotherapy (t2).

The study used next-generation sequencing (NGS) with a 139-gene lung cancer panel to assess ctDNA at ultra-deep coverage (30,000×). Advanced statistical models including time-dependent Cox regression were employed to eliminate immortal time bias.

"These findings offer a compelling rationale for integrating ctDNA-based stratification in future LS-SCLC trials and may help guide real-time decisions on the use of consolidation ICIs," Dr. Bi said.