Multiple sources, shared readouts: the attribution gap in circular RNA immunotherapy for esophageal squamous cell carcinoma

Therapeutic circular RNAs (circRNAs) are progressing from preclinical development to clinical evaluation, and esophageal squamous cell carcinoma (ESCC) may become a future indication for circRNA-based immunotherapy, potentially including first-line use. However, three focal sources-the intrinsic immunogenicity of exogenous circRNAs, the abundance of the endogenous circRNA pool, and patients' baseline interferon states-can act through different mechanisms but converge on the same readouts, including interferon output, protein yield, and immune phenotypes. Their individual contributions are therefore difficult to distinguish, complicating efforts to establish dose-response relationships. This Perspective examines this structural barrier to effect attribution and proposes strategies at three levels: product characterization and control, effect dissection, and baseline adjustment. We argue that studies of circRNA immunotherapy in ESCC and related settings should incorporate concurrent measurement of these three key, measurable sources at the design stage, with causal inference complementing association analyses to grade the reliability of attribution. Such an approach could help reduce attribution bias and provide a foundation for subsequent dose optimization and risk stratification.