Inclusion Criteria:

1. Females with a BMI > 30 kg/m2 wishing to retain fertility or females who are at high
risk of surgical complications due to co-morbidities or obesity

2. Over 18 years of age at time of randomisation

3. Histologically confirmed complex endometrial hyperplasia with atypia or grade 1
endometrioid endometrial adenocarcinoma on a curette or endometrial biopsy

4. CT scan of pelvis, abdomen and chest (or chest X-Ray) suggesting the absence of
extrauterine disease

5. Myometrial invasion on MRI of not more than 50%, for women with suspected
histologically confirmed Endometrial Cancer only

6. No lymph vascular invasion on curetting or pipelle

7. Serum CA125 ≤ 30 U/mL

8. No hypersensitivity or contraindications for mirena

9. Ability to comply with endometrial biopsies at specified intervals

10. Negative serum or urine pregnancy test in pre-menopausal women and women < 2 years
after the onset of menopause

11. No Mirena® IUD or Mirena® IUD inserted < 6 weeks prior to enrolment

Exclusion Criteria:

1. ECOG performance status > 3

2. Grade 1 endometrioid adenocarcinoma of the endometrium with myometrial invasion
deeper than 50% on MRI or any patients with grade 2 or grade 3 endometrioid
adenocarcinoma

3. Histological (cell) type other than endometrioid adenocarcinoma (sarcomas or high
risk endometrial e.g. papillary serous, clear cell)

4. Pregnant or planning to become pregnant during trial period

5. Prior treatment for EAC or EHA

6. Patients with a history of pelvic or abdominal radiotherapy

7. Unwilling to have additional endometrial biopsies or curettes or unable to attend
three monthly clinical assessments

8. Unable to provide informed consent or complete questionnaires

9. Evidence of extrauterine spread on medical imaging

10. Congenital or acquired uterine anomaly which distorts the uterine cavity

11. Acute pelvic inflammatory disease

12. Conditions associated with increased susceptibility to infections with microorganisms
(e.g., AIDS, leukaemia, IV drug abuse) according to the patients Medical History

13. Genital actinomycosis

14. Current other cancer

15. Breastfeeding mothers