Uterine cancer includes endometrial cancer and uterine serous carcinoma. Endometrial cancer is cancer of the inner lining of the uterus and consists of five histological types: adenocarcinoma, uterine carcinoma, squamous cell carcinoma, small cell carcinoma, transitional carcinoma, and serous carcinoma. Uterine sarcoma is a second type of uterine cancer, which forms in the myometrium or connective tissue of the uterus. Uterine cancer was the most common female reproductive system cancer diagnosis in Canada in 2010. With an incidence rate of 30.3 new cases per 100,000 women, uterine cancer represents 6.3% of all new cancers in women in this country. The mortality rate for uterine cancer was 5.4 deaths per 100,000 women in 2010. Uterine serous carcinoma is a rare, aggressive sub-type of endometrial cancer that accounts for 10% of new cases and is associated with 80% of endometrial cancer deaths. The treatment of endometrial cancer varies depending on several factors, including severity and stage of disease and involvement of the human epidermal growth factor receptor 2 (HER2). Overall, the prognosis for endometrial cancer is good. Patients with advanced or recurrent endometrial cancer are commonly treated with systemic chemotherapy (typically cisplatin plus doxorubicin with or without paclitaxel) or hormonal therapy, with varying response rates, ranging from 10 to 78%. The current standard of care for uterine serous carcinoma begins with comprehensive surgical staging followed by adjuvant chemotherapy with six cycles of carboplatin and paclitaxel, followed by vaginal cuff brachytherapy. Standard treatment for advanced or recurrent HER2-positive uterine serous carcinoma involves hysterectomy and surgical staging, followed by chemotherapy with carboplatin and paclitaxel. Targeting treatment toward the HER2 protein in patients with HER2-positive breast cancer has led to improved survival rates in that population. Specifically, the antibody trastuzumab is frequently used in combination with chemotherapy to treat HER2 overexpressing breast cancers. It has been estimated that between fourteen and eighty percent of uterine serous carcinomas are HER2 positive. While trastuzumab and biosimilars of trastuzumab (e.g., Ogivri, Trazimera and Herzuma) are indicated for early breast cancer, metastatic breast cancer, and metastatic gastric cancer, a Health Canada Notice of Compliance (NOC) does not exist for trastuzumab for patients with HER2-positive advanced or recurrent uterine or endometrial cancer. In addition, the pan-Canadian Oncology Drug Review (pCODR) Expert Review Committee (pERC) has not reviewed trastuzumab monotherapy or trastuzumab combination therapy in patients with HER2-positive advanced or recurrent uterine or endometrial cancer. In order to support decision-making on the use of trastuzumab monotherapy or trastuzumab combination therapy in patients with HER2-positive advanced or recurrent uterine or endometrial cancer, the purpose of this report is to summarize and critically appraise the relevant evidence regarding the clinical effectiveness and cost-effectiveness of trastuzumab combination therapy or trastuzumab monotherapy for HER2 positive advanced or recurrent uterine or endometrial cancer.