Zhou et al. Journal of Experimental & Clinical Cancer Research 2011, 30:72 http://www.jeccr.com/content/30/1/72 Page 6 of 7 Conclusions This meta-analysis strongly suggested that patients trea- ted with ZOL had a statistically significant higher risk of arthralgia and bone pain than those without ZOL treat- ment. Furthermore, patients treated with upfront ZOL had a significantly higher risk of bone pain than patients with delayed ZOL. More attentions should be paid to patients with musculoskeletal disorders. For patients with low risk of osteoporosis, immediate ZOL may be not needed due to additional adverse effects in some conditions. Or it can be stopped after the occurrence of these adverse events. Further randomized clinical trials with large sample size should be taken to evaluate the side effects of ZOL, especially for musculoskeletal disorders. List of abbreviations AI: aromatase inhibitor; CI: confidence interval; DFS: disease-free survival; OS: overall survival; RR: risk ratio; ZOL: zoledronic acid. Acknowledgements We are grateful to Dr. Jifu Wei (Clinical Experiment Center, the First Affiliated Hospital with Nanjing Medical University) for critical discussion in our study. This work was supported in part by Wu Jie-Ping Foundation (320.670010009), the National Natural Science Foundation of China (81071753), the Six Kinds of Outstanding Talent Foundation of Jiangsu Province (To Wei He), the Science and Education for Health Foundation of Jiangsu Province (RC2007054), the Natural Science Foundation of Jiangsu Province (BK2008476, BK2009438 and BK2010581), the Program for Development of Innovative Research Team in the First Affiliated Hospital of NJMU (IRT-008), and A project Funded by the Priority Academic Program Development of Jiangsu higher Education Institutions (PAPD). Author details 1Department of Breast Surgery, The First Affiliated Hospital with Nanjing Medical University, 300 Guangzhou Road, 210029 Nanjing, China. 2Department of Gerontology, Jiangsu Province Official Hospital, 65 Jiangsu Road, 210009 Nanjing, China. 3Department of Endocrinology and Metabolism, The First Affiliated Hospital with Nanjing Medical University, 300 Guangzhou Road, 210029 Nanjing, China. Authors’ contributions WH has contributed to the conception and design of the study, the analysis and interpretation of data, the revision of the article as well as final approval of the version to be submitted. WBZ and XAL participated in the design of the study, performed the statistical analysis, searched and selected the trials, drafted and revised the article. PLZ drafted and revised the article. TY participated in the design of the study and helped to revise the article. All authors read and approved the final version of the manuscript. 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