A Systematic Review and Meta‐Analysis of Risk Factors for Secondary Oral Squamous Cell Carcinoma After Allogeneic Hematopoietic Stem Cell Transplantation

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is widely used to treat patients with malignant and nonmalignant hematologic disorders. The development of secondary malignancies is recognized, especially secondary oral squamous cell carcinoma (OSCC). This study aimed to evaluate and summarize the risk factors for secondary OSCC after allo-HSCT. STUDY DESIGN: The search was conducted in 3 electronic databases for studies published up to May 2025. The quality of the identified studies was evaluated using the Newcastle-Ottawa Quality Assessment Scale for nonrandomized studies. The results were presented as risk ratios (RRs) with corresponding 95% confidence intervals (95% CI). RESULTS: Overall, 15 924 patients from 16 studies were included in the systematic review. The results show that, among many factors involved in HSCT, chronic graft-versus-host disease (cGVHD; RR = 4.01, 95% CI = 1.91-8.39, p = 0.0002), malignant primary diagnosis (RR = 0.40, 95% CI = 0.19-0.84, p = 0.02), and intensity of conditioning myeloablative therapy (RR = 0.41, CI = 0.17-0.98, p = 0.04) were found to be risk factors for secondary OSCC after allo-HSCT. CONCLUSION: Patients with cGVHD, with a primary diagnosis of malignant disease, or myeloablative intensity of conditioning are more likely to develop secondary OSCC. Our analysis of the literature shows patients after allo-HSCT that required close follow-up, especially examining oral mucosa regularly.