e13522 Background: Kinase domain duplication (KDD) has recently been recognized as oncogenic and targetable mutations in some cancers. EGFR KDD was identified as an oncogenic driver in lung cancer showing partial response to EGFR TKI. BRAF KDD was reported in diverse tumor types with clinical response to RAF-targeted therapy. We retrospectively investigated the prevalence of KDDs in multiple cancer types of a large Chinese population. Methods: 50742 unique cancer cases were analyzed by comprehensive genomic profiling (CGP). DNA was extracted from formalin-fixed paraffin-embedded specimens (FFPEs), fresh tissue, blood or plasma samples and sequenced with gene panels targeting 400+ cancer-relevant genes. Among them, 53 cases were detected with KDD of various kinases. Results: In this Chinese cohort, KDD was identified in 0.1% of the total population across multiple cancer types including lung cancer (39), breast cancer (5), gastric cancer (3), colorectal cancer (2), mucoepidermoid carcinoma (1), unknown (3). The median age at diagnosis was 54 which was younger than the 60 yrs median age of total population. The distribution of KDDs was in EGFR(34) MET(5), JAK1(2), BRAF(2), FGFR2(2), FGFR1(1), JAK2(1), LYN(1), MAP3K1(1), RAF1(1), RET(1), AKT3(1), and CDK8(1). Thirty-one lung cancer cases were detected with EGFR-KDD, including kinase duplications of exon18-25 (22), exon17-25 (6), exon18-26 (2), exon14-26(1). Three patients with EGFR-KDD exon18-25 showed partial anti-tumor response to target therapy. MET-KDD was exclusively found in lung cancer involving the duplication of MET exon15-21 (2), exon14-17 (1), exon15-16 (1) and exon12-21 (1) while FGFR1/2-KDD was observed only in gastric cancer. Two female patients with breast cancer were detected with JAK1-KDD at age of 45 and 37, respectively. The canonical BRAF-KDD of exon 10-18 was identified in one female patient diagnosed of lung adenocarcinoma at age of 49. Frequently altered genes in patients with KDD were TP53(72%), EGFR (23%), FAT1(13%), BRCA1(10%). MCL1 amplification, a known oncogenic alteration, was identified in fifteen patients (11 EGFR-KDD,2 MET-KDD, 1 BRAF-KDD, 1 JAK2-KDD), representing the most common copy number variation observed. Conclusions: Kinase KDDs were rare but potentially oncogenic mutations in diverse cancer types with clinical outcome of EGFR-KDD to target therapy in lung cancer. Cancer-type specific KDDs were identified including MET-KDD in lung cancer, FGFR1/2-KDD in gastric cancer and JAK1-KDD in breast cancer.