Smoking and Cancer: 12 Cancers, Secondhand Smoke, and What Quitting Does

The main points

• Cigarette smoke contains more than 7,000 chemicals; at least 69 can cause cancer.
• Smoking can cause cancer almost anywhere in the body.
• Quitting lowers the risk of 12 cancers and helps people who already have cancer.

How smoking causes cancer

Cancer is a group of diseases in which cells divide out of control and can invade or spread to other parts of the body through the blood and lymph systems. There are more than 100 types, most named for the organ or cell where they start.

Besides the chemicals that cause cancer outright, others weaken the body's defenses. Smoking:

• weakens the immune system, making it harder to kill cancer cells, so they can grow and spread;
• damages or changes DNA, which can set a cell growing out of control into a tumor.

Smoking causes about one in three cancer deaths in the United States.

Smoking can cause cancer almost anywhere in the body. Image from CDC's page.

The 12 cancers

Smoking causes cancer of the bladder; blood (acute myeloid leukemia); cervix; colon and rectum; esophagus; kidney and renal pelvis; larynx (voice box); liver; lung, bronchus and trachea; mouth and throat; pancreas; and stomach. Men with prostate cancer who smoke may also be more likely to die of it.

Lung cancer is the leading cause of cancer death for U.S. men and women, and smoking or secondhand smoke causes nearly 9 in 10 lung cancer deaths. People who smoke are about 25 times as likely to get lung cancer as people who don't — and their risk is higher today than in 1964, even though they smoke fewer cigarettes, perhaps because of changes in how cigarettes are made and what they contain.

Smokeless tobacco, such as chewing tobacco, causes cancer of the esophagus, mouth and throat, and pancreas.

Secondhand smoke — from burning cigarettes, cigars, hookahs or pipes, or breathed out by a smoker — causes lung cancer in people who have never smoked: more than 7,300 U.S. deaths a year.

For people with cancer

Smoking harms people with cancer at every stage, including after treatment. It raises the risk of death, including from the cancer, and of new smoking-related cancers, and may raise the chance of recurrence, weaken the response to treatment, and bring more complications and side effects.

What quitting does

Quitting is one of the most important things anyone who smokes can do, whatever their age or how long or how much they have smoked. It lowers the risk of all 12 cancers, and people with cancer who quit may lower their risk of death and improve their outlook. Compared with continuing to smoke:

Free help to quit: CDC.gov/quit.

Screening

Screening looks for cancer before symptoms appear, when treatment works best. It exists for three of the cancers smoking causes:

• Cervical — the HPV test and Pap test can prevent cervical cancer or find it early; CDC offers free or low-cost screening nationwide.
• Colorectal — can find precancerous polyps so they can be removed, and find cancer early.
• Lung — the U.S. Preventive Services Task Force recommends a yearly low-dose CT scan (the only recommended lung screening test) for people who:
• • have a 20 pack-year or greater smoking history (a pack-year is one pack a day for one year — so 20 years at a pack a day, or 10 years at two), and
  • smoke now or quit within the past 15 years, and
  • are 50 to 80 years old.

Yearly screening stops at age 81, after 15 years without smoking, or if a health problem seriously shortens life expectancy or would make the person unable or unwilling to have surgery for lung cancer.

Sources

Based on "Health Effects of Cigarettes: Cancer," Smoking and Tobacco Use, Centers for Disease Control and Prevention (September 17, 2024); a work of the United States government in the public domain. The source's stock photograph is not reproduced.