About four out of five cancers of the ovary produce abnormal levels of the protein CA125 in the blood. If treatment with either surgery or chemotherapy, or a combination of the two, is successful and the cancer is gone or greatly reduced, then the CA125 level should go back to normal.
When chemotherapy is given the drugs often go on working for some time after they are given. This means that sometimes the CA125 level may still be above normal at the end of a course of chemotherapy for ovarian cancer but it can still reduce further over the next month or so. If the CA125 remains abnormal after chemotherapy has been completed then it is likely that there are still cancer cells present which can regrow in the future. However there may only be very small amounts of cancer cells present as CA125 is a very sensitive measure of ovarian cancer and is often raised when all other tests and investigations are normal. If your CA125 remains above the normal level and is continuing to reduce with each course of treatment than your doctors may give you some extra chemotherapy, depending on how you are coping with the treatment.

If the CA125 level has stopped reducing than there may not be anything to be gained by continuing with chemotherapy and it is more likely that your doctors will simply continue regular check-ups and keep a watch on the CA125 level.

Many women find it very difficult to accept not having active treatment if the CA125 remains raised, but there is no evidence that giving further chemotherapy, before there is any obvious evidence of the cancer having come back, will improve the outcome of treatment. Ovarian cancer often grows quite slowly and for some women it can be a long time before it is necessary to give further chemotherapy.