What Is a Pack-Year? How to Calculate Your Smoking History and Lung Cancer Risk

The facts are sobering. Lung cancer is the leading cause of cancer death in the United States. It’s responsible for about 1 in 5 cancer deaths, according to the American Cancer Society.  

There is hope, however. When lung cancer is found early, it’s often more treatable, and the outcomes are better. Figuring out whether screening is right for you starts with one simple number: pack-years.

What Is Lung Cancer Screening?

Lung cancer often develops quietly. Early-stage lung cancer usually causes no symptoms. By the time you experience a lingering cough, chest pain or shortness of breath, the disease is typically more advanced.

Lung cancer screening uses a low-dose CT scan to look for signs of cancer in people who feel healthy. It uses less radiation than a standard CT scan while still creating detailed images of your lungs.

The benefits are well documented. Research shows people screened with low-dose CT had about 15% to 20% fewer lung cancer deaths than those screened with chest X-rays.

What Is a Pack-Year?

A pack-year is a way to measure how much you have smoked over your lifetime. It combines two things:

• How many packs of cigarettes you smoked per day.
• How many years you smoked.

One pack-year equals smoking one pack a day for one year. The more pack-years, the greater the lifetime exposure to tobacco and the higher the risk for lung cancer, even if you quit years ago.

How to Calculate Your Pack-Years

The formula is simple:

Packs smoked per day × Years smoked = Pack-years.

For example:

• 1 pack a day for 20 years = 20 pack-years
• 2 packs a day for 10 years = 20 pack-years
• ½ pack a day for 40 years = 20 pack-years
• 1½ packs a day for 30 years = 45 pack-years

If your smoking habits changed over time, calculate each period separately and add them together. For example, 1 pack a day for 10 years (10 pack-years) plus ½ pack a day for 20 years (10 pack-years) equals 20 pack-years.

How Pack-Years Factor Into Screening Guidelines

The U.S. Preventive Services Task Force (USPSTF) and the Centers for Disease Control and Prevention (CDC) recommend yearly low-dose CT screening for adults who:

• Are ages 50 to 80.
• Have a smoking history of 20 pack-years or more.
• Currently smoke or have quit within the past 15 years.

The American Cancer Society's guidelines go a step further. They recommend screening for people ages 50 to 80 with at least a 20 pack-year history, no matter how long ago they quit.

Because guidelines differ slightly, talk with your doctor to see whether lung cancer screening is right for you.

Next Steps If You Meet the Pack-Year Requirement

You’ve done the math and your number is 20 pack-years or more. Now what?

• Talk with your primary care provider. Review your smoking history, overall health and the benefits and possible risks of screening, such as false positives and follow-up testing.
• Check your coverage. Many insurance plans cover annual lung cancer screening for people who meet eligibility guidelines. Call your insurer to confirm.
• Schedule your screening. Screening is recommended once a year for as long as you remain eligible. A doctor's order is required. 
• Get support to quit. If you still smoke, quitting at any age lowers your risk. Free help is available by calling 1-800-QUIT-NOW.

If something is found, don't panic. Most findings on a screening scan are not cancer. Your provider may recommend a follow-up scan or additional testing to take a closer look.

Lung Cancer Screening at Witham

Witham offers quick, painless low-dose CT lung cancer screening close to home at two locations:

• Witham Health Services Main Campus – 2605 N. Lebanon Street, Lebanon
• Witham Imaging Services, Whitestown at Anson – 6085 Heartland Drive, Suite 105, Zionsville

Your results are sent to your provider, and you'll also see them in your Witham Patient Portal. A doctor's order is required. To schedule your lung cancer screening, call 765-485-8080 (Option 1).

Sources:

Centers for Disease Control and Prevention: Screening for Lung Cancer

American Cancer Society: Key Statistics for Lung Cancer

American Cancer Society: Lung Cancer Screening Guidelines

U.S. Preventive Services Task Force: Lung Cancer Screening