How is Ovarian Cancer detected if you have no utereous?

I am having to go in and have a hysterectomy and the doctor has left it up to me whether or not to have my overies removed. My mother died of Uterin cancer. I am 40 years old and do not plan on having any more children and I am already dealing with some early menopause symptoms. The doctor informs me that if I choose to not have them out at this time I will have to come back in and have them removed when I turn 45. Are the extra years with my overies going to make that much of a difference? My other question is how do they detect Ovarian cance if you do not have a utereous.

Thank you for your time, Kathrine