Esophageal radiosensitization has many molecular targets but little practice-ready clinical evidence

KEY POINTS

• The review searched PubMed for literature available through 30 April 2026, using esophageal cancer, ESCC, EAC, radiotherapy, radioresistance and radiosensitization as major terms. It deliberately combines mechanistic preclinical experiments with clinical investigations and organizes the evidence around the classical 6Rs of radiobiology.
• Under repair, the authors emphasize DNA-damage-response pathways involving γ-H2AX, PARP1, ATM/ATR, DNA-PKcs, Ku70/80, RAD51 and the MRN complex. PARP inhibition and interference with homologous recombination or nonhomologous end joining are among the more translationally attractive approaches, but most esophageal-specific radiosensitization evidence remains preclinical.
• Redistribution and repopulation involve cell-cycle checkpoints and cancer stem-cell biology, including p53/p21, ATM/CHK signaling, CDK4/6 and the YAP1–CDK6 axis. The review considers CDK4/6 inhibition a potentially translatable strategy, but combination approaches intended specifically to enhance RT still lack sufficient clinical efficacy and toxicity data.
• Reoxygenation and the tumor microenvironment add another layer of resistance through HIF-1α signaling, ROS homeostasis, cancer-associated fibroblasts, macrophages and extracellular-matrix remodeling. For example, the review describes a CXCL1–CAF–collagen feedback loop that may increase DNA repair and radioresistance, but notes that no clinical intervention targeting this pathway has yet been validated in esophageal cancer.
• Radiation-induced immune modulation forms the sixth R, reactivation. RT can alter MHC-I expression, inflammatory cytokines and PD-L1 signaling, potentially changing sensitivity to immune checkpoint blockade. However, the authors distinguish this biological rationale from proven radiosensitization: many immune and stromal mechanisms described in esophageal models have not yet produced validated treatment-selection strategies.
• The review also highlights crosstalk between ferroptosis, autophagy and apoptosis. Nrf2/SLC7A11/GPX4 signaling, PLK1 and other pathways can modify ferroptotic response to radiation; critically, the authors state that no targeted ferroptosis agent has yet entered an esophageal cancer clinical trial. Lobaplatin is presented as a more clinically mature candidate among apoptosis-related approaches, while most other proposed agents remain experimental.
• Biomarker development is similarly promising but immature. FGF5 promoter hypermethylation achieved AUC 0.712, sensitivity 65% and specificity 76% for treatment response in reported cohorts, while radiomic models showed pooled sensitivity and specificity around 0.83–0.89 but suffered from poor reproducibility and limited external validation. Most mechanistic evidence throughout the review comes from esophageal squamous-cell carcinoma, leaving a major evidence gap for adenocarcinoma.

CLINICAL TAKEAWAY

SOURCE

Cancers