Breast cancer is the most common type of cancer, and one of the leading causes of cancer-related deaths worldwide. Smoking is linked to a higher risk of breast cancer in some people.

The exact cause of breast cancer is unknown, but some risk factors make it more likely a person could develop breast cancer.

A person cannot change certain breast cancer risk factors such as genetics or age, but they can change others, such as smoking.

Continue reading to learn about the link between cigarette smoke exposure and breast cancer, how smoking affects breast cancer treatment, and more.

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According to the World Health Organization (WHO), breast cancer is the most common type of cancer and the leading cause of cancer-related death among women worldwide.

Smoking can increase the risk of cancer, as certain chemicals in tobacco products may lead to uncontrolled cell growth within a person’s body. Although smoking is not considered a direct cause of breast cancer, smoking is linked to a higher risk in some people.

A 2017 study found that smoking was associated with a modest but significantly increased risk of breast cancer in certain women, including:

  • women who started smoking in adolescence, or by the age of 17
  • women who started smoking before or at the time of their first period
  • women who started smoking 1 to 4 years after their first period
  • women with a family history of breast cancer who smoked at any time in their lives
  • women of childbearing age who are BRCA2 mutation carriers
  • women who smoked for at least 10 years
  • women who had stopped smoking for less than 20 years
  • women who smoked more than 5 years before their first full-term pregnancy
  • women who smoked more than five cigarettes per day

According to the American Cancer Society’s 2021 estimates for breast cancer in women in the United States, there will be 281,550 new diagnosed cases with 43,600 deaths from the disease.

The WHO states that in 2020 there were 2.3 million women diagnosed with breast cancer with 685,000 deaths from the disease worldwide.

In 2019, the Center for Disease Control and Prevention (CDC) published that approximately 1 in 5 U.S. adults (50.6 million) currently used any tobacco product.

The WHO states that over 80% of the 1.3 billion tobacco users worldwide live in low- and middle-income countries.

Additional statistics from a 2017 study published in Breast Cancer Research include:

  • Women who smoked at some point in their lives were 14% more likely to develop breast cancer than those who had never smoked.
  • Women who started smoking before age 17 had a 24% increased risk, while those who started smoking between ages 17 and 19 had a 15% increased rate of breast cancer.
  • Smoking for over 10 years increased the risk of developing breast cancer by 21%, while those who smoked for over 30 years had a slightly higher risk (22%).
  • Of the women who had quit smoking, there was still a 28% increased risk of developing breast cancer for those who had quit for less than 10 years.
  • For women with a family history of breast cancer, their risk for breast cancer was highest if they started smoking by age 20 (56%).

Per a 2017 study, smoking is associated with the breast cancer subtype Luminal A. Luminal A cancers tend to grow slowly and have a good outlook.

Treatments for breast cancer include:

Smoking can increase complications of breast cancer treatment.

According to a 2020 review, smoking during radiation treatment can cause complications, including:

  • a poorer response to treatment
  • poorer 2-year survival rates
  • recurrence of cancer
  • a possible increase in cardiovascular events such as heart attack, stroke, or congestive heart failure

The study mentions that people who smoke still experienced a higher risk of major complications, such as difficulty healing after surgery and after breast reconstruction, even if they did not receive radiation therapy.

Nicotine is the addictive ingredient in tobacco products. It does not cause cancer by itself. However, a 2021 study suggests that nicotine can encourage breast cancer to spread to a person’s lungs.

Because cannabis smoke contains similar ingredients to tobacco, smoking cannabis may be a risk factor for the development of lung cancer.

However, a 2019 meta-analysis found no link between smoking cannabis and breast cancer development.

The authors of the review do note that because there was not enough evidence linking smoking cannabis to other cancers, larger-scale studies are needed.

Passive smoking, also known as secondhand smoke, is the combination of smoke from the burning end of a cigarette and the smoke that people exhale.

According to the CDC, secondhand smoke contains over 7,000 chemicals. Hundreds of these chemicals are toxic, and about 70 can cause cancer.

According to a 2018 study, secondhand smoking increases the risk of lung and breast cancers in women.

A 2015 case control study in China also suggests a strong positive association with passive smoking and an increased risk of breast cancer among postmenopausal women.

Doctors have long suspected a link between smoking and breast cancer risk, but according to the advocacy group, research results are mixed. More research is needed to understand the potential link between secondhand smoke and breast cancer risk.

Smoking is harmful, and there is no safe level of exposure to tobacco. Quitting smoking lowers a person’s risk for developing many smoking-related diseases, such as breast cancer.

Most people quit smoking using a combination of medicine and behavioral changes.

Some tips for quitting smoking include:

  • Discuss smoking cessation medications with a doctor.
  • Set a quit smoking date.
  • Start an exercise or walking program.
  • Try acupuncture.
  • Practice mindful meditation.
  • Avoid smoking triggers.
  • Try a quit smoking app.
  • Find a buddy who also wants to quit smoking.
  • Use a telephone quit-line such as 800-QUIT-NOW (800-448-7848).
  • Contact smoking cessation help programs, such as those offered by the American Cancer Society and the American Lung Association.

Find more tips on quitting smoking here.

Research shows that smoking is associated with an increased risk of breast cancer in some women, specifically women who started smoking during adolescence, smoked at least two packs per day, or smoked prior to their first full-term pregnancy.

Smoking is a significant health problem and one of the few potentially modifiable risk factors for breast cancer development.

People who do not smoke should avoid starting. For people who do smoke, many programs are available to help with quitting.