Letrozole as Maintenance Therapy for Post-surgical Endometrial Cancer Patients With NSMP

Inclusion Criteria:

1. Older than 18 years old;
2. Initial diagnosed with stage I-IV(FIGO2009) endometrial epithelial cancer, regardless of pathological types;
3. Surgery must have included a hysterectomy, bilateral salpingo-oophorectomy and sentinel node biopsy; pelvic lymph node sampling and para-aortic lymph node sampling are optional;
4. Life expectancy of 2 or more years.
5. Confirmed NSMP with intermediate or higher prognostic risk according to post-operative clinical pathological assessment and molecular classification;

   1. Intermediate prognostic risk group:

      * Stage lB endometrioid + Iow-grade\* + LVSI negative or focal
      * Stage IA endometrioid + high-grade\*+ LVSI negative or focal
      * Stage IA non-endometrioid (serous, clear cell, undifferentiated carcinoma, carcinosarcoma, mixed) without myometrial invasion
   2. High-intermediate prognostic risk group:

      * Stage I endometrioid + substantial LVSI, regardless of grade and depth of invasion
      * Stage lB endometrioid high-grade\*, regardless of LVSI status
      * Stage II
   3. High prognostic risk group:

      * Stage Ill-IVA with no residual disease
      * Stage I-IVA non-endometrioid (serous, clear cell, undifferentiated carcinoma, carcinosarcoma, mixed) with myometrial invasion, and with no residual disease
   4. Advanced Metastatic:

      * Stage III-IVA with residual disease
      * Stage IVB Low grade: G1-2; High grade:G3;
6. Received conventional adjuvant therapy after surgery according to the latest version of NCCN or ESGO/ESTRO/ESP guidelines;
7. Patients with residual tumor after surgery (any single site) must have achieved complete response or partial response after post-operative adjuvant therapy;
8. Expected start of letrozole maintenance within 3 months after adjuvant therapy;
9. Adequate organ function as defined by the following criteria:

   * White blood cell (WBC) ≥ 3000/μL or Absolute neutrophil count (ANC) ≥1500/μL
   * Platelets ≥100,000/μL
   * Serum Aspartate transaminase (AST) and/or serum alanine transaminase (ALT) ≤ 2 times upper limit of normal (ULN)
   * Serum creatinine ≤2 times ULN
10. Karnofsky score ≥60;
11. Eastern Cooperative Oncology Group (ECOG) Performance status ≤2;
12. Ability to take anti-thyroid drugs, calcium, vitamin D or bisphosphonates together.

Exclusion Criteria:

1. Endometrial stromal tumor;
2. Recurrent endometrial cancers;
3. Patients with low prognostic risk according to post-operative clinical pathological assessment ( Stage IA endometrioid + low-grade\* +LVSI negative or focal);
4. Patients require no adjuvant therapy after surgery;
5. Negative expression in estrogen receptor or progesterone receptor according to post-operative Immunohistochemistry;
6. Received other adjuvant therapy within 6 months before surgery: including neoadjuvant therapy, hormone therapy, targeted therapy, immunotherapy and biotherapy, etc;
7. Patients with contraindications for letrozole;
8. Patients with other malignant tumors;
9. History of vital organ transplantation;
10. History of immune disease and need to take immunosuppressor;
11. Uncontrolled psychiatric illness or other situations that would limit compliance with study requirements;
12. History of drug abuse;
13. Participated in other clinical trials;
14. No ability or intention to receive letrozole maintenance/sign the consent/obey the study requirements.