When you stop taking letrozole, most persistent side effects should improve within a week or 10 days, and as long as you have taken it for at least 5 years, then letrozole should continue to reduce the risk of breast cancer coming back for many years after you stop taking it. Letrozole is usually taken for 5 years, but may be recommended for up to 10 years depending on individual circumstances. The American Society of Clinical Oncology (ASCO) recommends that 10 years should be the maximum duration of therapy, based on their 2019 clinical practice guideline update.

Do not stop taking letrozole without talking to your treatment team first. If you are not tolerating it well due to side effects, sometimes temporarily stopping it or switching to another hormone drug may be considered. If letrozole stops working and your breast cancer comes back, your specialist may prescribe another hormone drug. Not taking letrozole for the recommended time may increase the risk of your breast cancer coming back. Taking letrozole for long periods of time has been associated with an increased risk of bone fractures and heart side effects.