What is the life expectancy with untreated stage 3 -b ovarian cancer?

Ovarian cancer : It depends on the type of ovarian cancer. Even at stage iiib not all ovarian cancers require chemotherapy. However, if you are talking about stage iiib invasive serous carcinoma (the most common type), then the average survival without adequate therapy would be < 1 year. With proper surgery and chemotherapy, more than 60% will live 5 years or more.