Assessment of durable chemoimmunotherapy response via circulating tumor DNA in advanced esophageal squamous cell carcinoma

Immune checkpoint inhibitor (ICI)‐based therapies have shown promising advances for the first‐line treatment of advanced or metastatic esophageal cancer (EC). However, few studies concerning the identification of patients who achieve durable response from ICIs have been previously reported. In the present study, pre‐ and on‐treatment plasma circulating tumor DNA (ctDNA) were analyzed in 10 patients with advanced esophageal squamous cell cancer (ESCC) receiving first‐line chemoimmunotherapy. Patients with decreased molecular tumor burden index (mTBI) >7% experienced longer progression‐free survival (PFS) and durable clinical benefit (DCB, PFS ≥ 6 months). In addition, five patients showed stable disease at first scan, all three patients with decreased mTBI > 7% achieved DCB, while two cases with decreased mTBI ≤ 7% experienced non‐DCB. Our results demonstrate that ctDNA monitor might help identify which ESCC patients respond to chemoimmunotherapy. We collected peripheral blood samples before and during first‐line chemoimmunotherapy in patients with stage IV esophageal squamous cell cancer. Molecular tumor burden index (mTBI) was calculated based on ctDNA. Patients with decreased mTBI >7% achieved longer progression‐free survival than patients with decreased mTBI ≤7%.