Some kinds of ovarian cancer can be found on ultrasound before they have spread. My tumor was 9 cm. and had not spread. It was visible on ultrasound. From what I have recently read, though, it appears that most ovarian cancers spread shortly after the original tumor comes into existence. This is one reason why 75-80% of ovarian cancer cases are diagnosed at a late stage. Not very encouraging, I am afraid.
There is no test that can detect ovarian cancer. Any type of sonograms, etc...can show growth, masses, cysts, whatever you want to call them....but they cannot tell if they are cancerous or not. Being scanned every 4 months will give the doctors a good picture of what is going on inside, but, even being scanned cannot prevent a diagnosis of OvCa.