Tumor mutational burden (TMB) is a biomarker that helps determine the response to immune checkpoint inhibitor treatments. However, the prognostic value associated with TMB in the absence of immunotherapy is not certain. This study aims to investigate the prevalence of high TMB, along with its association with overall survival (OS) in patients not treated with immunotherapy.
This retrospective cohort study included a total of 2,589 eligible patients aged 18 years or older with any of the following solid cancer types: cervical, vulvar, small cell lung, cervical, vulvar, small cell lung, salivary gland, mesothelioma, neuroendocrine tumor, and thyroid. The primary outcome of the study was overall survival, as analyzed by the Kaplan-Meier method and the Cox proportional hazards model.
The median TMB was found to be 2.6 mut/Mb, and 332 patients had TMB-H. The prevalence of TMB-H was the highest in patients with small-cell lung cancer (40%), followed by neuroendocrine tumors (29.3%). The incidence was the lowest among patients with mesothelioma (1.2%) and thyroid cancer (2.7%). The adjusted hazard ratio for the overall survival of patients treated with vs. without TMB-H was 0.94.
The research concluded that the prevalence of TMB-H varied depending on the tumor type. It was also found that TMB-H was not a factor associated with OS in patients with the considered cancer types.