Breast Cancer Facts

After skin cancer, breast cancer is the most common cancer affecting women in the United States. In 2018, an estimated 330,000 women will develop breast cancer. About 80% of these women will have invasive breast cancer. This is breast cancer that has grown into nearby breast tissue or has spread to lymph nodes or other areas of the body. The remaining cases are non-invasive, or carcinoma in situ. This cancer has not spread anywhere and remains in its original area of the breast.

What are the different types of breast cancer?

There are several types of breast cancer including:

Ductal carcinoma in situ (DCIS), which develops and remains in the cells lining the milk ducts. About 20% of new cases are this very early and treatable type.
Invasive ductal carcinoma, which starts in the milk ducts and invades nearby breast tissue. This is the most common type.
Invasive lobular carcinoma, which starts in the glands that produce milk and invades nearby breast tissue. About 10% of breast cancers are this type.
Other types, which include inflammatory breast cancer, Paget’s disease of the nipple, phyllodes tumor, and angiosarcoma. These are rare types.

Who gets breast cancer?

Breast cancer mainly affects women. One in 8 American women will get breast cancer at some point during her lifetime. This translates to an average risk of about 12%. However, men can also develop it. Annually, about 2,500 men will face the diagnosis in the United States. A man’s chance of getting breast cancer during his lifetime is about 1 in 1,000.

There are other trends in breast cancer statistics including:

Breast cancer is more common in women over the age of 50. The rate is highest in women over the age of 70.
In women under the age of 45, the disease is more common in African American women than women of other races.
Most breast cancers—85%—develop in women with no family history of the disease.
If a woman has a mother, sister or daughter with breast cancer, her risk of the disease nearly doubles.
Up to 10% of breast cancers are linked to genetic mutations, such as BRCA1 and BRCA2. These mutations can quadruple a woman’s risk of the disease. Women also develop cancer earlier with these mutations.

How does breast cancer affect quality of life?

Health-related quality of life (HRQoL) describes how a disease affects a person’s overall well-being. It includes mental, physical and emotional health. It also includes social and sexual functioning and your ability to perform daily functions and roles. Non-health factors, such as finances, can play a role in HRQoL as well.

It’s not surprising that breast cancer can affect quality of life. During treatment, it can be difficult to deal with side effects and symptoms, such as fatigue. Doctors and healthcare providers recognize this aspect of cancer treatment. Managing issues and worries that affect HRQoL is an important part of cancer care. And this continues after treatment as women transition to survivorship.

Breast cancer does not always have a negative effect on life. Some women report positive effects on spirituality, general outlook on life, and taking pleasure in life. Researchers are exploring the benefits of exercise, social support, and mentoring others with the disease on long-term HRQoL in breast cancer survivors.

What causes breast cancer?

Cancer in general starts when normal checkpoints fail to limit cell growth and replication somewhere in the body. For breast cancer, this failure happens in breast cells, most frequently the cells lining the milk ducts. Breast cells begin dividing without control and can invade other tissues. Gene changes are at the root of this abnormal growth. Most of the time, these gene changes accumulate throughout a woman’s lifetime. Eventually, the cells these genes are in become very abnormal. Less often, gene changes are inherited.

The specific triggers that cause the gene changes in breast cells remain unclear, however there are risk factors. As is true for most adult cancers, age is the strongest risk factor because oftentimes it takes many years for enough gene changes to tip the scale from a normal cell to a cancer cell.

Other factors known to increase a woman’s risk of breast cancer include:

Prior radiation therapy to the chest
Family history of breast cancer
BRCA mutations
First menstrual period after age 12
Menopause after age 55
Long-term use of hormone replacement therapy for menopause (combined estrogen and progestin HRT for more than five years)
First full-term pregnancy after age 30
No history of full-term pregnancy
Heavy and long-term alcohol consumption
Obesity (as identified in postmenopausal women not using hormone replacement)
Lack of physical activity for a long period

How is breast cancer diagnosed?

Mammogram screening finds most breast cancers in early stages. Often, this is before breast cancer symptoms, including a lump, even develop. Diagnostic imaging tests are necessary if a mammogram shows something suspicious or a woman finds a lump. However, the only way to know for sure if an area is cancerous is to biopsy the breast tissue in the area.

When breast cancer is present, doctors will stage it as follows:

Stage 0 is DCIS.
Stage I (1) is the earliest form of invasive breast cancer.
Stage II (2) is also early invasive breast cancer, but the tumor is either larger than stage I or has spread to local lymph nodes.
Stage III (3) is locally advanced breast cancer that has spread to nearby tissues and lymph nodes.
Stage IV (4) is metastatic breast cancer that has spread to a distant body site(s).

Diagnosis also involves grading the tumor’s growth rate and identifying tumor receptors. The three main receptors on breast cancer tumors are estrogen receptors, progesterone receptors, and HER2 (human epidermal growth factor receptor 2). Tumors can have one, two, three or none of these receptors.

Tumors with hormone—estrogen or progesterone—receptors are hormone receptor positive. This is the case for most breast cancers. When HER2 is present, the cancer is HER2 positive. This is the case for about 20% of breast cancers. About 10% are positive for HER2 and one hormone receptor and a small number are positive for all three receptors. When a tumor lacks all three receptors, it is triple-negative breast cancer. Up to 20% of breast cancers are this more aggressive form.

How many people die of breast cancer?

Doctors often talk about cancer survival as a 5-year survival rate. This rate shows how many people with the disease are still alive five years after diagnosis. For breast cancer, a relative survival rate is more common. It compares the survival of women with breast cancer to those in the general population. This rate shows how much the disease can shorten life. A relative survival rate of 80% means someone with the disease is 80% as likely as someone in the general population to be alive after five years.

The 5-year relative survival rates for breast cancer stages are as follows:

Stage 0 or I: 100%
Stage II: 93%
Stage III: 72%
Stage IV: 22%

Overall, more than 40,000 people will die this year from breast cancer.

What are common treatments for breast cancer?

Breast cancer treatment options depend on the stage. Common treatments include:

Surgery, which is the main treatment for most cases of breast cancer
Radiation therapy, which can be useful either before or after surgery
Chemotherapy, which can also be useful before or after surgery or as a main treatment, with or without radiation therapy
Hormone therapy, which is useful for hormone receptor-positive tumors
Targeted therapy, which is useful for HER2-positive or hormone receptor-positive tumors

Additional breast cancer facts

Breast cancer treatment has come a long way in the last 30 years. The incidence of breast cancer in the United States has been declining since the year 2000. The death rate has been declining as well, especially in women younger than 50 years of age. Today, there are more than 3.1 million breast cancer survivors in the United States. This includes women who have completed treatment and those still receiving it.

October is Breast Cancer Awareness Month. Learn more about breast cancer at the Susan G. Komen Breast Cancer Foundation and Breastcancer.org.