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.

If some cancer cells survive the chemotherapy then, even if the CA125 has gone back to normal, those cells will at some point start to grow again and will cause the cancer to come back. This re-growth of the cancer may be quite slow and can take many months or even years before any symptoms develop.

Because CA125 is a very sensitive measure of ovarian cancer it is often raised long before any symptoms of the cancer are apparent and when all other tests and investigations are normal.

If your CA125 is rising again then you might think that the sensible thing is to start more chemotherapy. In fact there is no evidence that starting treatment as soon as the CA125 starts to rise gives a better outcome than if treatment is delayed until symptoms appear.

As there is no advantage in giving chemotherapy immediately, and because it may be a long time before symptoms develop and because giving chemotherapy often leads to side-effects and interferes with the quality of life, most doctors recommend delaying further treatment until problems actually develop.

This is often a hard thing to come to terms with but the advice your doctor has given you is absolutely right.