To see if megestrol acetate plus Levonorgestrel-releasing intrauterine system (LNG-IUS) will not be inferior to returning the endometrial tissue to a normal state than megestrol acetate alone in patients with early endometrial cancer.

After diagnosed of endometrioid endometrial cancer (EEC) by hysteroscopy, patients will be enrolled. Age, waist circumstances, blood pressure, basic history of infertility, blood pressure, serum lipid level and side effects will be collected. Blood tests, including fasting blood glucose (FBG), postprandial blood glucose (PBG), fasting insulin (FINS), SHBG, sex hormone levels, blood lipids and anti-müllerian hormone(AMH) will be performed before treatment to evacuate their metabolic conditions.

Patients are randomized to 1 of 2 treatment groups. Patients will receive MA (megestrol acetate) 160 mg by mouth daily for at least 3 months on Arm I. Patients will receive MA 160 mg plus LNG-IUS insertion for at least 3 months on Arm II. Then an hysteroscope will be used to evaluate the endometrial condition every 3 months, and the findings will be recorded. For patients with EEC, complete response (CR) is defined as the reversion of endometrial disease to proliferative or secretory endometrium; partial response (PR) is defined as regression to simple or complex hyperplasia without atypic or atypical hyperplasia; no response (NR) is defined as the persistence of the disease; and progressive disease (PD) is defined as the progression of endometrial lesions. Continuous therapies will be needed in PR, NR or PD.

As the reason of the low response rate of LNG-IUS alone in EC patients (nearly 50%), and the potential limitation of LNG-IUS to focal cancer lesion in endometrial cavity, the investigators did not add LNG-IUS alone as a single control group.

After completion of study treatment, 2 months of maintenance treatment will be recommended for patients with CR, and participants will be followed up for 2 years.

Inclusion Criteria:

• Primarily have a confirmed diagnosis of endometrioid endometrial cancer based upon hysteroscopy
• MRI parameters shows there's no myometrial invasion, extension beyond corpus, or enlarged lymph nodes
• Have a desire for remaining reproductive function or uterus
• Need to be able to undergo correlative treatment and follow-up

Exclusion Criteria:

• Acute liver disease or liver tumor (benign or malignant) or renal dysfunction
• Pregnancy or suspicion of pregnancy
• Have a history of EAH or EC and have disease relapse during Merina insertion
• Under treatment of high-dose progestin therapy more than 3 months in recent 6 months
• Congenital or acquired uterine anomaly including fibroids if they distort the uterine cavity
• Confirmed diagnosis of malignant tumor in genital system
• Acute severe disease such as stroke or heart infarction or a history of thrombosis disease
• Hypersensitivity or contradiction to any component of this product
• Ask for removal of the uterus or other conservative treatment
• Smoker(>15 cigarettes a day)