Hello, I am @cancerdoctor, a radiation oncologist in South Korea.
I had worked in Seoul National University Hospital in Korea, and I am working for public health now.
I am here in order to provide several important note regarding cancer.
"What is the cause of breast cancer?"
This is one of the questions that I get the most in a clinic. Breast cancer is the most common cancer among women worldwide. Breast cancer is caused by mutations of genes regulating cell growth. The gene mutation can be either herditary or aquired.
"Is breast cancer genetic?"
Approximately 10% of breast cancer patients have familial breast cancer with autosomal dominant inheritance pattern. Also, 20-25% of breast cancer patients have already family members with breast cancer.
Three important tumor suppressor genes discovered in patients with familial breast cancer were p53, BRCA1, and BRCA2. Individuals with a germline mutation in BRCA1 have a lifetime risk of breast cancer of 65 to 90%. Also, these individuals have an elevated lifetime risk of ovarian cancer, uterine cancer, colorectal cancer, and prostate cancer.
A famous movie actress, Angelina Jolie underwent a preventative bilateral mastectomy (removing all of her breast tissues) in 2013 after her BRCA1 gene mutation had been identified. Her doctor told her that she had an 87 percent risk of breast cancer and a 50 percent risk of ovarian cancer, before her decision. There had been some controversy about whether this was the right thing to do, but genetic testing has made it possible to predict the risk of breast cancer to some extent.
"I am worried about getting breast cancer. Do I have to get a gene test?"
Gene test can be done after 4-8 weeks after a blood test at a hospital or examination center. However, not everyone needs to get this expensive test. Because, incidences of these gene mutations are less than 1%. The National Comprehensive Cancer Network (NCCN) recommends to get the gene test when you meet any of the following:
- A known mutation in a cancer susceptibility gene with the family
- Breast cancer diagnosed age ≤ 50 yrs
- Triple negative (ER-, PR-, HER2-) breast cancer diagnosed ≤ 60 yrs
- Two breast cancer at any age, and
- ≥1 close blood relative (1st- to 3rd-degree relatives) with breast cancer ≤ 50 yrs, or
- ≥1 close blood relative with invasive ovarian cancer at any age, or
- ≥2 close blood relatives with breast cancer, prostate cancer, and/or pancreatic cancer at any age, or
- Personal history of pancreatic cancer at any age, or
- From a population at increased risk (i.e. Ashkenazi Jews)
- Male breast cancer
If you do not have one of these, there is no need to be anxious about the gene mutations, nor get a gene test done.
"If I am not the case, am I safe from breast cancer?"
No. Other 70-80% of breast cancer patients don't have any familial history of breast cancer. You need to be careful of risk factors related to breast cancer as well.
Robson ME, Boyd J, Borgen PI, et at. Hereditary breast cancer. Curr Probl Surg2001;38(6):387–480.
Cancer risks in BRCA2 mutation carriers. The Breast Cancer Linkage Consortium. J Natl Cancer Inst 1999;91(15):1310–1316.
NCCN Clinical Practice Guidelines in Oncology, Breast Cancer. Version 2.2017. Accesible at www.nccn.org