en Health Technology Assessment Health Technology Assessment Original Research Original Research <strong>Background: </strong>Trastuzumab in combination with chemotherapy has long been established as a standard treatment for HER2-positive patients in early stage breast cancer (BC). The present study aimed at assessing the effectiveness of trastuzumab adjuvant therapy in early stage BC in overall survival (OS) and disease-free survival (DFS).<br> <strong>&nbsp;&nbsp; Methods:</strong> A systematic review and meta-analysis was performed to evaluate the effectiveness of trastuzumab adjuvant therapy. PubMed, Cochrane library, Scopus, Web of Science, and Embase databases were searched for relevant RCTs from the beginning to February 2017. Quality assessment of studies was conducted using the Cochrane Risk of Bias Tool. The desired outcomes were OS and DFS.<br> <strong>&nbsp;&nbsp; Results:</strong> A total of 1818 articles were identified first, however, only 11 studies were eligible to be included in this study. Our findings and meta-analysis results revealed that trastuzumab is effective in increasing OS (OS hazard ratio: -0.286 &plusmn; 0.049, 95%CI (-0.381, -0.191)) and improving DFS (DFS hazard ratio: -0.419&plusmn; 0.077, 95%CI (-0.569, -0.269)). The most serious but negligible side effect of trastuzumab is congestive heart failure.<br> <strong>&nbsp;&nbsp; Conclusion: </strong>Adding trastuzumab as adjuvant therapy in early stages of BC in HER2 positive patients could increase OS and DFS of the patients effectively.<br> &nbsp; Trastuzumab, Breast Cancer, Herceptin, Meta-analysis, Adjuvant Therapy 515 520 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-1117&slc_lang=en&sid=1 Majid Davari 200319475328460036605 200319475328460036605 No Department of Pharmacoeconomics and Pharmaceutical Administration, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran, & Pharmaceutical Management and Economics Research Center, Tehran University of Medical Sciences, Tehran, Iran. Bahman Amani 200319475328460036606 200319475328460036606 No Department of Health Management and Economics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Fariborz Mokarian 200319475328460036607 200319475328460036607 No Breast cancer Research center, Isfahan University of Medical Science, Isfahan, Iran. Mohsen Hoseini 200319475328460036608 200319475328460036608 No Department of Biostatistics and Epidemiology, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran. Arash Akbarzadeh 200319475328460036609 200319475328460036609 No Department of Epidemiology and Biostatistics, School of Public Health, Tehran Univer-sity of Medical Sciences, Tehran, Iran. Nastaran Heidarzadeh Khoramabadi 200319475328460036610 200319475328460036610 Yes Department of Drug and Food Control, School of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran.