HER2 (human epidermal growth factor receptor 2), a protein encoded by the HER2 gene, promotes growth; therefore, breast cancers with an excess of this protein tend to grow and spread quickly.1 However, breast tumors that have an excess of this protein allow the use of specific therapies such as HER2-targeted therapies.2 Some of the more common side effects of HER2-trageted therapies include diarrhea, nausea, vomiting, rash, and fatigue. In rare cases, more serious side effects can occur as a result of taking HER2-trageted drugs such as heart or lung problems.3

Since HER2-targeted drugs may be given with chemotherapy, side effects due to chemotherapy [MB1] may be experienced. Additionally, taking these drugs together increases the likelihood of developing some side effects of chemotherapy that are generally uncommon. These side effects may include osteoporosis (weak bones) and cataracts (cloudy eyes). Certain chemotherapy drugs also have the potential to lead to heart problems, meaning taking these drugs together increases the risk.3

References

1.     Types of Breast Cancer: Triple Negative, ER-Positive, HER2-Positive https://www.webmd.com/breast-cancer/breast-cancer-types-er-positive-her2-positive (accessed Apr 30, 2021).  

2.     Triple-negative Breast Cancer: Details, Diagnosis, and Signs https://www.cancer.org/cancer/breast-cancer/understanding-a-breast-cancer-diagnosis/types-of-breast-cancer/triple-negative.html (accessed Apr 27, 2021).

3.     What are Anti-HER2 Therapies? https://www.breastcancer.org/treatment/targeted_therapies/anti-her2-therapy (accessed Jun 11, 2021).

 [MB1]Link ‘chemotherapy side effects’ article