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1. Introduction =============== Osteosarcoma (OS) is the most common primary bone malignancy which is approximately 19% of all bone tumors. Treatments usually combine aggressive standard-of-care surgical techniques and alkylating agent-based chemotherapy regimens, as improved survival was reported in combined chemotherapy compared to surgical only treatment.^\[[@R1]\]^ However, sarcomas are usually diagnosed at an advanced stage, most primary therapeutic modalities including surgery, chemotherapy and biological therapies are not particularly effective. As one of the lowest survival rates among various cancers, although the 5-year survivorship of OS patients is 70% with localized disease, the survival rate drops to 30% for metastatic cases.^\[[@R2]--[@R4]\]^ And significant differences were observed on the treatment effect even from patients received same therapeutic modalities.^\[[@R5]\]^ Hence, it is of great clinical significance to explore the underlying mechanisms of disease development and progression. Excision repair cross-complementation group 1 (ERCC1) and excision repair cross- complementation group 2 (ERCC2) are important enzymes in nucleotide excision repair (NER) pathway responsible for restoring cisplatin-induced DNA damages, such as intrastrand and interstrand crosslinks (ICLs). Germline polymorphisms in DNA damage repair genes, such as ERCC1 and ERCC2, could have an important impact on both survival rates and chemotherapy treatment-related toxicity.^\[[@R6]\]^ Therefore, the identification of predictive markers could lead to improved drug selection and treatment outcomes.^\[[@R7],[@R8]\]^ However, the published results from previous studies on the association of ERCC1 and ERCC2 polymorphism with prognosis in chemotherapy-treated osteosarcoma in China were inconsistent. For example, some studies showed that ERCC1 rs11615 is associated with OS survival treatment with cisplatin,^\[[@R9]\]^ and the ERCC1 rs11615CC genotype had a longer overall survival compared with the TT genotype.^\[[@R10]\]^ While there are also results suggested that the ERCC1 rs11615 TT genotype and ERCC2 rs1799793 AA genotype were associated with longer overall survival when compared with those with the wild-type genotype.^\[[@R11]\]^ The conclusions on ERCC2 polymorphism were also inconsistent. Some studies suggested no association between ERCC2 rs13181 polymorphisms and overall survival in patients with osteosarcoma under cisplatin-based chemotherapy.^\[[@R12]--[@R14]\]^ However, a recent meta-analysis found that the ERCC2 rs13181 polymorphisms might influence osteosarcoma prognosis.^\[[@R15]\]^ Thus, we performed a meta-analysis based on the most updated qualified studies trying to make an accurate estimation of such association in Chinese population. 2. Methods ========== This study was performed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statements. All data were extracted from previous studies, and no direct patient contact or influence on patient care was involved in this research. Thus, ethical approval and informed patient consent were not required. 2.1. Search strategy and data collection ---------------------------------------- Literature search was carried out by 2 investigators (Dabiao Liu and Xuesong Liu) independently from the PubMed (1966--2015), Embase (1980--2015) and the Web of Science (1945--2015) using the search term based on a combination of Medical Subject Headings (MeSH) and text words relating to "ERCC1", "ERCC2", " osteosarcoma", and "chemotherapy". Dabiao Liu reviewed the literature and extract the data. Possible review author\'s bias, however, might exist due to limited literature resources. The retrieved literature (up to November 11, 2015) was further screened