A new study finds more than a third of breast cancer patients stop taking the drugs that could prevent a recurrence of their disease.

The study from Northwestern University surveyed nearly 700 women with post-menopausal breast cancer.

Thirty-six percent said they quit the medications early because of side effects. Those include extreme joint pain, nausea, hot flashes and mood swings.

Researchers say doctors need to get better at managing the side effects linked to the drugs, so patients can stay on them longer.