e17523 Background: Germline DNA repair gene (DRG) mutations has emerged as a potential determinant of cancer risk and therapeutic response in PCa. Despite substantial advances in delineating the germline mutation in DRGs among Caucasian population, the prevalence of mutations in DRGs are largely unknown among a large series of unselected prostate cancer patients in Chinese population. Methods: We enrolled 1003 prostate cancer patients from three different hospitals in China, unselected for family history of cancer or age at diagnosis. All patients received germline genetic testing using a clinician-selected multi-gene panel. The 18 DNA repair genes and HOXB13, which has established or emerging potential clinical actionability in PCa, were analyzed in our study. Results: A total of 94 (9.7%) deleterious germline mutations were identified among the 1003 unselected prostate cancer patients. Of these, 5.6% patients carried a BRCA1 or BRCA2 mutations (5.2% in BRCA2 and 0.4% in BRCA1), 3.6% patients carried other DRG mutations (including 10 genes) and 0.5% patients carried HOXB13 mutations. Besides, variants with uncertain significance (VUS) were found in approximately 45% patients. We also divided 633 metastatic PCa patients into 542 de novo metastastic PCa and 91 recurrent metastastic PCa and found mutation frequencies did not differ between these two groups (9.0% vs 11.6%, p = 0.6). Patients with younger age of onset or family history of cancers were more likely to harbour germline mutations in DRGs. However, the rate of germline mutations were still at a high level for patients more than 70 years old (6.7%) and patients without family history of cancers (7.5%). There is no statistically significant difference in the mutation frequencies between patients with metastasis and without metastasis (7.5% vs 9.2%, p = 0.4), which may be because 85% patients without metastasis in our cohort were in high to very high risk group or have lymph node metastasis. Conclusions: To our knowledge, our study reported the largested series of Chinese PCa patients who received germline genetic testing. Our study provided a rationality for germline genetic testing criteria from high risk to metastastic PCa regardless of family history considering the high proportion. In addition, we recommended a multigene panel covering 13 genes ( ATM, BRCA1, BRCA2, CHEK2, FANCA, HOXB13, MSH2, MSH6, NBN, PALB2, RAD51C, RAD51D, TP53) in China. Nevertheless, the high prevalence of VUS (45%) in Chinese PCa patients warrant further efforts.
645P Prediction of BRCA2 mutations in prostate cancer patients according early onset, metastatic phenotypes or family history of breast/ovary cancer
