What is HER2 Positive Breast Cancer?
HER2-positive breast cancer is a type of breast cancer in which the human epidermal growth factor receptor 2 (HER2) protein, encoded by the HER2 gene, is expressed. Breast cancers in which the HER2 gene is highly amplified so that the HER2 protein becomes over-expressed are said to be HER2 "positive". HER2 promotes the rapid growth and spread of this highly aggressive type of breast cancer, which is often resistant to hormonal therapy.
HER2-positive breast cancer not only spreads rapidly, but can also show recurrence, compared to HER2-negative breast cancer. It should be noted that some HER2-positive breast cancers can become HER2-negative over time. Likewise, HER2-negative breast cancer can sometimes become HER2-positive.
Facts & Statistics about HER2 Positive Breast Cancer
Some essential facts and figures pertaining to HER2-positive breast cancer are presented below:
- Approximately 12 percent of US women are likely to develop invasive breast cancer at some point in their lives.
- HER2-positive breast cancer represents approximately 20 percent of all breast cancers.
- HER2-positive breast cancer varies with age and race.
- Prevalence of HER2-positive breast cancer among all types of breast cancer is estimated to be 19 percent for women aged ≤49 years and 15 percent aged ≥50 years.
Since figures are not available for the survival rate specifically for HER2-positive breast cancer, the general statistics for all breast cancers have been presented. These data are based on the SEER (Surveillance, Epidemiology, and End Results) Program Database of the National Cancer Institute (NCI), National Institutes of Health (NIH), USA.
Five-year Relative Survival Rate for Breast Cancer
|Stage of Cancer||Survival Rate (%)|
|Stage 0 and Stage I||100|
What are the Causes of HER2 Positive Breast Cancer?
The primary cause of HER2-positive breast cancer is the mutation of the HER2 gene. In this regard, the following observations should be noted:
- The HER2 gene mutation stimulates excessive cell growth and division.
- The HER2 protein causes normal cells to grow uncontrollably like aggressive cancer cells.
- The HER2 protein is present at high levels in approximately 30 percent of breast cancers, making them HER2-positive.
- High levels of HER2 protein are linked to a greater likelihood of metastasis, relapse, and lower patient survival.
Two other possible causes that have been suggested include environmental factors and lifestyle. However, these have not been verified scientifically.
- Population-based estimate of the prevalence of HER-2 positive breast cancer tumors for early stage patients in the US - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5094051/)
- HER2-positive breast cancer: What is it? - Mayo Clinic - (https://www.mayoclinic.org/breast-cancer/expert-answers/faq-20058066)
- HER2 status - (https://www.breastcancer.org/symptoms/diagnosis/her2)
- Targeted therapy for breast cancer - (https://www.cancer.org/cancer/breast-cancer/treatment/targeted-therapy-for-breast-cancer.html)
- HER2’s genetic link to breast cancer spurs development of new treatments - (https://www.cancer.gov/research/progress/discovery/HER2)
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VCU Massey Cancer Center physician-researcher Charles E. Geyer, Jr., M.D., supported clinical trials that demonstrated that trastuzumab significantly improves the long-term survival of HER-2 positive breast cancer patients.