Breast cancer is the most common cancer among women, accounting for about one-third of all cancers in women. The mutation of a single cell or multiple cells of breast tissue is the central process by which cells multiply rapidly to form breast cancer. The mutations can be acquired through exposure to environmental carcinogens, or inherited from one’s parents. Individuals with inherited gene mutations from their parents have a 60-80% chance of developing breast cancer.

BRCA1 and BRCA2 are two tumor suppressor genes present in the breast that keeps in check, the growth of tumor cells. Mutations in these two genes can result in an uncontrolled growth of cells, leading to breast cancer formation. Another dominant oncogene also plays a significant role in 25% of the human breast cancer cases. The product of this gene is known as erB2 (or HER2 neu). Expression of HER2 in breast cancer is associated with a poor prognosis in cancer patients.

The treatment of breast cancer primarily involves surgical excision of the tumor from the body, to arrest the further growth of the mass. Even after tumor removal, there is a chance of recurrence. Mostly, chemotherapy, radiotherapy, or a combination of these two are used to check tumor growth following the surgical excision. Nevertheless, other treatment modalities have also been attempted. And, one such modality is the use of drugs that target HER2 amplification.  

A recent phase III clinical trial was directed to explore the effectiveness and efficacy of two drug combinations that target HER2 amplification. In this study, around 5,000 patients with HER2-positive breast cancer, following surgical excision, were randomly assigned to groups to receive either a single drug with standard chemotherapy and a placebo (Trastuzumab) or a combination of two drugs (Trastuzumab and Pertuzumab). The researchers believed that by combining the two drugs, it might help establish a complete barrier to cancer cell growth. 

The study found a slightly better result for the combination of drugs. More than 94% of the patients did not develop invasive cancer, which accounts for a 1% improvement over patients treated with Trastuzumab alone. The prognosis was also improved, as the combination drug decreased the chance of getting invasive cancer by 19%. The study also predicted that 8% of the patients diagnosed with breast cancer have early HER2-positive disease and they may be benefitted from this combination therapy.

The lead author of the study Gunter von Minckwitz, from Germany, said that “women with HER2-positive breast cancer used to have a worse prognosis than those with HER2-negative cancer, but the advent of HER2-targeted therapy changed the outlook for these women”. He also added that “our early findings suggest that we may be able to further improve outcomes for some women by adding a second HER2-targeted treatment, without increasing risk for serious side effects”.

References: 

1. Adding a Second HER2 Blocker May Lower Chance of Invasive Breast Cancer for Some Women [Internet]. ASCO. 2017 [cited 2017 Jun 10]. Available from: https://www.asco.org/about-asco/press-center/news-releases/adding-second-her2-blocker-may-lower-chance-invasive-breast
2. Fentiman IS, D’Arrigo C. Pathogenesis of breast carcinoma. Int J Clin Pract. 2004 Jan;58(1):35–40.
3. Kasper DL. Harrison’s principles of internal Medicine. 19th ed. McGraw-Hill Education