Zheng Wang1, Xiaoguang Li2, Lin Zhang1, Yan Xu3, Mengzhao Wang3, Li Liang4, Peng Jiao5, Yuanming Li2, Shurong He1, Jun Du1, Lei He1, Min Tang6, Mingjun Sun1, Li Yang1, Jing Di1, Guanshan Zhu7, Lin Li6, Dongge Liu1. 1. Department of Pathology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, P.R. China. 2. Department of Minimally Invasive Tumor Therapies Center, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, P.R. China. 3. Department of Respiratory and Critical Care Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, P.R. China. 4. Department of Cancer chemotherapy and Radiation sickness, Peking University Third Hospital, Beijing, P.R. China. 5. Department of Thoracic Surgery, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, P.R. China. 6. Department of Medical Oncology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, P.R. China. 7. Amoy Diagnostics Co., Ltd, Xiamen, P.R. China.
Abstract
BACKGROUND: Sputum cell-free DNA (cfDNA) is a valuable surrogate sample for assessing EGFR-sensitizing mutations in patients with advanced lung adenocarcinoma. Detecting EGFR exon 20 p.T790 M (p.T790 M) is much more challenging due to its limited availability in tumor tissues. Exploring sputum cfDNA as an alternative for liquid-based sample type in detecting p.T790 M requires potential improvement in clinical practice. METHODS: A total of 34 patients with EGFR-sensitive mutation-positive lung adenocarcinoma and acquired resistance to the first generation of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) were enrolled. The sputum samples, and paired tumors and/or plasma samples were tested for p.T790 M mutation and concordance of p.T790 M status among the three sample types was analyzed. RESULTS: The overall concordance rate of p.T790 M mutation between sputum cfDNA and tumor tissue samples was 85.7%, with a sensitivity of 66.7% and a specificity of 100%. The sensitivity for detecting p.T790 M in sputum cfDNA was 100%, 66.7%, and 0% in the three sputum groups of malignant, satisfactory but no malignant cells, and unsatisfactory, respectively. The combined results of plasma cfDNA testing and sputum cfDNA testing further increased the sensitivity to 100% for p.T790 M detection in satisfactory but no malignant cells sputum group. CONCLUSION: These findings revealed that cfDNA from malignant or satisfied but no malignant cells sputum is considered suitable for detecting p.T790 M mutation in patients with acquired resistance to first or second-generation EGFR-TKIs. The sputum cytological pathological evaluation-guided sputum cfDNA testing assists in significantly improving the sensitivity of p.T790 M detection, bringing significant value for the maximal application of third-generation EGFR-TKIs in second-line treatment.
BACKGROUND: Sputum cell-free DNA (cfDNA) is a valuable surrogate sample for assessing EGFR-sensitizing mutations in patients with advanced lung adenocarcinoma. Detecting EGFR exon 20 p.T790 M (p.T790 M) is much more challenging due to its limited availability in tumor tissues. Exploring sputum cfDNA as an alternative for liquid-based sample type in detecting p.T790 M requires potential improvement in clinical practice. METHODS: A total of 34 patients with EGFR-sensitive mutation-positive lung adenocarcinoma and acquired resistance to the first generation of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) were enrolled. The sputum samples, and paired tumors and/or plasma samples were tested for p.T790 M mutation and concordance of p.T790 M status among the three sample types was analyzed. RESULTS: The overall concordance rate of p.T790 M mutation between sputum cfDNA and tumor tissue samples was 85.7%, with a sensitivity of 66.7% and a specificity of 100%. The sensitivity for detecting p.T790 M in sputum cfDNA was 100%, 66.7%, and 0% in the three sputum groups of malignant, satisfactory but no malignant cells, and unsatisfactory, respectively. The combined results of plasma cfDNA testing and sputum cfDNA testing further increased the sensitivity to 100% for p.T790 M detection in satisfactory but no malignant cells sputum group. CONCLUSION: These findings revealed that cfDNA from malignant or satisfied but no malignant cells sputum is considered suitable for detecting p.T790 M mutation in patients with acquired resistance to first or second-generation EGFR-TKIs. The sputum cytological pathological evaluation-guided sputum cfDNA testing assists in significantly improving the sensitivity of p.T790 M detection, bringing significant value for the maximal application of third-generation EGFR-TKIs in second-line treatment.