The present invention relates to : - use of a 2,3-dihydroimidazo[1,2-c]quinazoline compound, or of a pharmaceutical composition containing same, as a sole active agent, or of a combination of a) said compound or a pharmaceutical composition containing said compound and b) one or more further active agents, for the preparation of a medicament for the treatment or prophylaxis of endometrial cancer (hereinafter abbreviated to "EC"), particularly 1st line, 2nd line, relapsed, refractory, type I or type II EC, or endometriosis； - combinations of a) said compound and b) one or more further active agents； - a pharmaceutical composition comprising said compound as a sole active agent for the treatment of endometrial cancer (hereinafter abbreviated to "EC"), particularly 1st line, 2nd line, relapsed, refractory, type I or type II EC, or endometriosis； - a pharmaceutical composition comprising a combination of a) said compound and b) one or more further active agents； - use of biomarkers which is the loss of tumor suppressor PTEN or FBXW7, for predicting the sensitivity and/or resistance of a cancer patient to said compound and providing a rationale-based dosage to increase sensitivity and/or to overcome resistance； - a method of determining the loss of tumor suppressor PTEN or FBXW7； and - a method for determining perturbations in PIK3CA, PIK3CB, PIK3CD, PIK3CG, PIK3R1, PIK3R2, PIK3R3, PIK3R4, PIK3R5, FGFR1, FGFR2, FGFR3 and/or FGFR4.
