Bariatric Surgery for Fertility-Sparing Treatment of Atypical Hyperplasia and Grade 1 Cancer of the Endometrium

Inclusion Criteria: * BMI ≥ 35 * Diagnosis of grade 1 endometrioid endometrial cancer or complex atypical hyperplasia * Clinical stage 1 disease - no evidence of metastatic disease beyond the uterus by imaging performed (MRI, CT) * ECOG status \<2 * Desire for fertility preservation * No contraindications to progestin intrauterine device (IUD) * Have signed an approved informed consent form Exclusion Criteria: * Evidence of myometrial invasion or extra-uterine disease on imaging * High grade or p53 endometrial cancer * History of other malignancies, except if curatively treated with no evidence of disease for \> 5 years * Previous major upper abdominal surgery (ex. previous bariatric surgery, splenectomy, partial gastrectomy, liver resection, bowel resection). Appendectomy, cholecystectomy, hernia repair, and caesarean section are acceptable procedures for inclusion. * Current use of weight loss medication. NB: patients taking glucagon-like peptide 1 (GLP-1) agonists (e.g., OZEMPIC) for the treatment of diabetes will not be excluded. * Contraindications to sleeve gastrectomy * Medical co-morbidity with end-organ dysfunction * Unable to understand and participate in the informed consent process * Currently pregnant * Active smoking in ≤6 months * Active substance use disorder * Current untreated or severe psychiatric issue