Does Breast Cancer Increase Your Risk for Other Types of Cancers?

Breast cancer is one of the most common types of cancer affecting women. According to the World Health Organization (WHO), 2.3 million women were diagnosed with breast cancer, and 685,000 lost their lives globally in 2020.

As of 2020, 7.8 million women have been diagnosed with breast cancer and are alive in the last five years.

Breast cancer survivors are at risk for different health conditions - fatigue, mental health issues, and breast cancer recurrence - to name a few. They must also be aware of the higher risk they carry for developing a second non-breast cancer.

People who have had breast cancer in the past are at higher risk for developing other types of cancers, including:

- Stomach cancer
- Esophageal cancer
- Colon cancer
- Uterine cancer
- Ovarian cancer
- Sarcoma
- Salivary gland cancer
- Acute Myeloid Leukemia (AML)
- Melanoma

A 2006 study collected data from 13 different cancer registries in places like Singapore, Canada, Australia, and Europe. The study analyzed the data of 525,527 women and followed them for 10+ years.

According to the study, when compared to women who did not have a history of breast cancer, women with past or present breast cancer had:

- 48% increased risk for ovarian cancer
- 35% increased risk for stomach cancer
- 60% increased risk for thyroid cancer
- 29% increased risk for melanoma
- 27% increased risk for kidney cancer
- 24% increased risk for lung cancer
- More than 2 times increased risk for soft tissue sarcoma

Another study analyzed the risk of Secondary Non Breast Cancers (SNBCs) in 58,068 Dutch women diagnosed with breast cancer between 1989 and 2003. According to the study, women who had breast cancer in the past had a small but significant risk for developing esophageal cancer, stomach cancer, colon cancer, rectum cancer, uterus cancer, ovarian cancer, soft tissue sarcoma, acute myeloid leukemia (AML), and non-Hodgkin’s lymphoma.

Genetic Factors Influencing Risk For Breast And Other Cancer

The BRCA1 Gene

The BRCA1 gene (BRCA1, DNA repair associated gene) produces a tumor suppressor protein. This protein is considered beneficial as it hinders uncontrolled cell division, thereby lowering cancer risk.

Abnormal changes (or variations) in this gene can lead to low or no production of the tumor suppressor protein and increase one’s risk for developing cancers.

A study reported that BRCA1 variations lead to breast and ovarian cancers and also increase the risk of other cancers like colon cancer (11.1%), pancreatic cancer (3.6%), and gastric cancer (5.5%).

The BRIP1 Gene

The BRIP1 gene (BRCA1 interacting protein C-terminal helicase 1) contains instructions for producing a protein that repairs double-strand breaks in DNA.

Abnormal changes in this gene result in lower production of this protein, which increases the risk of many types of cancers. Cancers associated with variations in this gene are:

- Breast cancer
- Medulloblastoma (brain tumor)
- Tumors in the central and peripheral nervous systems
- Kidney cancer
- Bone cancer

The PALB2 Gene

The PALB2 gene (Partner And Localizer Of BRCA2 gene) contains instructions for producing a protein that works with the BRCA2 protein to repair damaged DNA and suppress tumor growth. Abnormal changes in this gene affect the ability of the BRCA2 gene to prevent tumor cell formation.

Apart from breast cancer, this gene is associated with the risk for:

- Ovarian cancer
- Lung cancer
- Prostate cancer

The CHEK2 Gene

The CHEK2 gene (Checkpoint kinase 2) is also a tumor suppressor gene and produces a kinase enzyme protein called CHK2.

Abnormal changes in this gene increase the risk of developing breast cancer by two times. It also increases the risk of:

- Ovarian cancer
- Colorectal cancer
- Prostate cancer
- Kidney cancer
- Thyroid cancer

The PTEN Gene

The PTEN gene produces an enzyme that acts as a tumor suppressor. Almost all tissues in the body have this enzyme in specific quantities. This enzyme prevents the abnormal division of cells by encouraging self-destruction (a process called apoptosis) of these cells. In people with past or present breast cancer diagnoses, variations in this gene can result in an increased risk of:

- Bladder cancer
- Head and neck squamous carcinoma
- Lung cancer
- Prostate cancer
- Bile duct cancer

Non-Genetic factors

Exposure To Radiation

One of the main non-genetic factors that increase a person’s risk of developing other cancers is radiation exposure.

There are three basic radiotherapy treatment solutions for breast cancer.

1. Three-dimensional Conformal Radiotherapy (3D-CRT)

2. Intensity-Modulated Radiotherapy (IMRT)

3. Volumetric Modulated Arc Therapy (VMAT)

Many studies report a higher risk of second cancer because of radiation exposure.

A large study analyzed the risk of second cancers in 46,176 breast cancer survivors. According to the study, one out of 200 women who had received radiation therapy for breast cancer had a higher risk of being diagnosed with other cancers.

Type of Chemotherapy

Chemotherapy is a treatment that uses various drugs to kill abnormally growing tumor cells in the body. It is the most common treatment option for cancer.

Some types of chemo drugs given during breast cancer treatment are associated with an increased risk for developing other types of cancers.

Chemo agents that are linked with second cancer risks are:

- Platinum-based chemicals
- Anthracycline topoisomerase II inhibitors
- Alkylating agents

Patients who go through chemotherapy for a longer time or get treated with higher doses of drugs are at a higher risk of developing other cancers.

Age

While patients who had exposure to radiation therapy and chemotherapy were at higher risk for developing second non-breast cancers, people under the age of 40 who received these treatments were at more risk than the elderly who received treatment.

Smoking

Smoking increases the risk of breast cancer and all other cancers. Smokers diagnosed with breast cancer are at higher risk for developing other cancers in the future when compared to non-smokers.

A 1994 study tried to find the relationship between smoking, breast cancer, radiation therapy, and the risk of second cancers. According to the study, radiation therapy for breast cancer increased the risk of developing other cancers in smokers and non-smokers. However, in smokers, this risk was much higher.

Recommendations To Bring Down The Risk Of Breast And Other Cancers

Genetic Testing

Genetic testing can be a good aid for treatment planning and risk management if:

- You are a cancer survivor
- You are less than 40 years and are diagnosed with breast cancer
- Your first and second-degree relatives have been diagnosed with breast cancer

Genetic testing will look for specific genes that can increase your risk for breast and other cancers. It will tell you if you are at higher risk for second cancer. In case you belong to the high-risk category, regular screening can help you.

Analyze The Risks In Your Chemotherapy and Radiation Therapy Procedures

Talk to your doctor about the dosage and type of chemotherapy and radiation treatment you will be receiving for your breast cancer. Some treatments may increase your risk for breast cancer than others.

Adopt Healthy Habits

Some lifestyle changes can lower your risk of developing cancer.

- Quit smoking
- Limit alcohol intake to 1 drink a day
- Stay away from processed, frozen, and packaged foods as much as possible
- Cook fresh food at home
- Include a lot of antioxidants in your diet to protect your cells
- Maintain a healthy weight
- Practice regular physical activity
Get regular cancer screening done

Do Not Fear

The fear of breast cancer recurrence and the fear of developing second cancers can lead to high stress. Stress causes abnormal changes in the cells and can be a cause for cancer recurrence. Fear and stress lead to unwanted behaviors like alcohol abuse, smoking, and excessive eating. All these also increase the risk of developing other cancers. Practicing mindfulness and talking to a mental health expert might help you in controlling stress.

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Summary

Breast cancer is associated with a higher risk of developing a second non-breast cancer.
Certain types of cancer like stomach cancer, colon cancer, uterus cancer, ovarian cancer, sarcoma, and Acute Myeloid Leukemia (AML) can develop after a breast cancer diagnosis.
Both genetic and non-genetic influences increase a breast cancer survivor’s risk for developing other types of cancers.
Abnormal changes in genes like the CHEK2, BRCA1, PTEN, ATM, and TP53 can increase the risk of breast and other cancers.
Non-genetic factors like age, radiation exposure, the intensity of chemotherapy, and lifestyle habits like smoking also increase the risk of developing second non-breast cancers.
A genetic test can tell you if you are at risk for developing a second non-breast cancer after a breast cancer diagnosis.
Following a healthy lifestyle, keeping away fear, and choosing the right radiation and chemotherapy procedures can help bring down the risk of second cancer considerably.