What is the effect of ending trastuzumab treatment early in older breast cancer patients?

This paper evaluated early discontinuation of trastuzumab (Herceptin) therapy and how cardiovascular events (disease associated with the heart and blood vessels) associated with this affect survival in older women with breast cancer.

Human epidermal growth factor receptor 2 (HER2) is a protein that can be found on cancer cells. This protein promotes cell growth. Trastuzumab is used to treat cancer that has the HER2 protein present. Trastuzumab can cause cardiotoxicity (damage to heart muscle), especially in older women. Cardiotoxicity can then lead to stopping trastuzumab treatment early.  However, it is not clear what the impact of early discontinuation of trastuzumab treatment has on women. 

585 women aged 67-94 years old were studied. 41% of women ended trastuzumab therapy early.  Whether or not cancer had spread to the lymph nodes and types of chemotherapy regimen undertaken were associated with completion of trastuzumab treatment. 

Women who ended trastuzumab early were more likely to have heart failure, atrial fibrillation (abnormal heart rhythmn) and other cardiovascular events. 25.1% of women who ended trastuzumab treatment early and 7.2% of women who completed trastuzumab treatment had a cardiovascular event within 45 days of the last treatment (either before or after the last treatment). Cardiovascular events were associated with a 3.54 times greater risk of death.

Women who did not complete trastuzumab treatment were more likely to have higher mortality (death) rates but this was not found to be statistically significant. 78.5% of patients who had a cardiovascular event ultimately completed the course of trastuzumab therapy. 

The authors concluded that reducing cardiovascular events from trastuzumab treatment could possibly improve overall survival in older women. 

Patients who received trastuzumab were assumed to have human epidermal growth factor receptor 2 present.