The incidence of endometrial cancer is increasing at an alarming rate. This trend parallels the rising rate of obesity, the most significant risk factor for endometrial cancer. Young women with obesity and endometrial cancer or atypical hyperplasia who want to maintain their fertility are treated with progestin therapy, such as progestin intra-uterine device (pIUD), which is associated with a mediocre response rate and high recurrence rate, and does not address the underlying cause, obesity. Therefore, the investigators want to assess whether the addition of a weight-loss drug to pIUD will improve their oncologic, reproductive and metabolic outcomes.

The research aims to answer the question: "Does the addition of a Glucose-dependent Insulinotropic Polypeptide (GIP)/Glucagon-like Peptide-1 (GLP-1) co-agonist to standard progestin treatment lead to a higher complete response rate compared to historical response rates using progestin alone in young patients with endometrial cancer/atypical hyperplasia who wish to preserve their fertility?". This is a multicentre single arm open-label phase II clinical trial to assess the complete pathologic response as determined by endometrial sampling after 48 weeks of tirzepatide (GIP/GLP-1 co-agonist) and progestin therapy in patients with BMI ≥ 27 who have endometrial cancer/atypical hyperplasia and desire fertility preservation.