Observational Study of Women With Endometrial Cancer Who Receive the Standard Treatment for Their Disease

Screening Inclusion Criteria:

* ECOG performance status 0-1 or KPS ≥ 70%
* Age ≥ 18 years
* Endometrioid adenocarcinoma histologic diagnosis on endometrial biopsy or dilatation and curettage
* No evidence of extrauterine disease, or suspicious pelvic lymph nodes, or distant metastases, or cervical invasion on pre-operative conventional imaging studies (Pelvic +/- Abdomen CT or MRI or sonogram, or body PET scan) and physical examination (uterine confined by exam and imaging )
* Suitable candidate for surgery
* Planned surgical treatment including hysterectomy in combination with SLN biopsy and a bilateral salpingo-oophorectomy
* No history of second primary cancer (invasive or in situ) within the past 5 years, not including non-melanoma skin cancer
* Approved and signed informed consent
* No history of neoadjuvant chemotherapy or radiotherapy for endometrial cancer
* No history of prior pelvic or abdominal radiotherapy

Screening Exclusion Criteria:

* Extrauterine disease, or gross lymph node involvement, or cervical invasion suspected on pre-operative imaging studies and physical examination (disease not uterine confined clinical stage \> I)
* Contraindication for SLN mapping
* The planned treatment is not surgery, or the surgical treatment does not include hysterectomy in combination with SLN biopsy and a bilateral salpingo-oophorectomy

Eligibility Inclusion Criteria

Patients will be classified in the study cohort (part 2; n=182) according to surgical treatment received, final post hysterectomy and staging pathologic report, and planned adjuvant treatment. The inclusion criteria are specified below.

Study Cohort (n=182)

A patient will be enrolled in the study cohort if all the following criteria are met:

* At surgery, the patient must undergo:

  * Hysterectomy
  * Bilateral salpingo-oophorectomy, unless already performed (including allowing unilateral salpingo-oophorectomy if unilateral salpingo-oophorectomy already performed)
  * Bilateral pelvic SLN mapping (bilateral sentinel nodes are negative for malignancy)
* On the final pathologic report, the patient must have a diagnosis of:

  * Stage I intermediate-risk endometrial endometrioid cancer (Grade 1 or Grade 2 with ≥ 50% myometrial invasion or Grade 3 with \<50% myometrial invasion, including non-invasive disease)
  * Negative pelvic peritoneal cytology
* Adjuvant treatment as recommended by the multidisciplinary team must be as follows:

  * No adjuvant treatment, or
  * Intravaginal radiation only

Eligibility Exclusion Criteria

* There is intra-operative detection of extra-uterine disease or grossly involved lymph nodes
* Presence of any positive pelvic nodes including micrometastasis and isolated tumor cells (ITC)
* Hysterectomy is not performed
* Bilateral salpingo-oophorectomy is not performed, unless already performed (unilateral salpingo-oophorectomy is allowed if unilateral salpingo-oophorectomy already performed)
* Failed unilateral or bilateral SLN mapping
* Patient undergoes a complete unilateral or bilateral pelvic lymphadenectomy
* Patient undergoes a radical type C hysterectomy
* Stage IA endometrioid cancer Grade1 or 2 and myometrial invasion \<50%
* Stage IB Grade 3 endometrioid cancer
* Non-endometrioid histology: Serous, clear cell, carcinosarcoma, undifferentiated, or de-differentiated histology noted on final hysterectomy pathology
* Empty unilateral or bilateral sentinel lymph nodal packet(s)
* Positive peritoneal cytology