A Word on Pack Years

A pack year is the parameter clinicians use to quantify a person‘s exposure to cigarette smoke. Briefly, to calculate a pack-year, multiply the number of years a person smoked by how many packs they smoke per day. A smoker who smoked a pack a day for twenty years is considered a twenty pack-year smoker.

Smoking tobacco cigarettes increases the risk of lung cancer but there is no magic threshold where the risk of lung cancer suddenly occurs. Lung cancer risk increases with each cigarette.

For people at significant risk of lung cancer, screening for lung cancer with an annual Chest CT decreases the risk of dying from lung cancer by 20-24%.

But what amount of smoking produces a significant risk for lung cancer?

Although not smoking is best, smoking a few is better than smoking a lot. Screening a patient at low risk of lung cancer doesn’t decrease the risk of dying from lung cancer but does expose them to excess radiation from an unnecessary Chest CT.

So what amount of smoking produces a significant risk for lung cancer to require lung cancer screening?

Honestly no one knows exactly.

However, we do know that cigarette smoke exposure affects each person differently. So the amount of smoking that puts a person at significant risk for lung cancer varies amongst individuals. Therefore, the amount of cigarettes a person smoked is never going to be the best determinant of lung cancer risk.

But right now, we do not have a better metric. So we use the pack-year.

Anyone with a twenty pack-year history, between 50 and 80 who smoked within the past 15 years, should speak to their doctor about getting screened for lung cancer. Screening saves lives.

But what if someone smoked a pack a day for 19 years and then quit? Its bad for their health to tell them to smoke another year just to qualify for lung cancer screening.

What if the person never really counted how much they smoked or can’t really remember when they started?

Or like most people, what if their smoking habit changed over the years. They started with a few on weekends, grew to a pack a day habit until something bad happened where they increased to two packs per day until they recovered and are working on being healthy again and have been cutting down. Good luck figuring out that person’s pack-year!

So what to do in these cases?

Lung Cancer Kilts says, do your best but don’t sweat it. Because…

-       Some people smoke the entire cigarette whereas some people let it mostly burn out in the ashtray. Still counted as one cigarette.

-       Ten percent of smokers reported different pack-year answers when asked one month later that changed their candidacy for lung cancer screening.

-       A person’s lung cancer risk does not markedly rise the moment they hit the twenty pack-year mark.

All of these reasons make the pack-year an inaccurate parameter prone to changes based on a person’s recollection that does not describe the absolute threshold for lung cancer risk.

So you do your best.

-       Its ok to guestimate.

-       We know most people tend to underestimate their smoking habit. So its ok to round up.

-       Its ok to multiple the number of years a person smoked by their highest number of packs per day that they smoked for at least one year.

-       Its ok to discuss this with your physician.

Currently, several biomarkers are being developed that will provide an individualized  determination of a patient’s true lung cancer risk. These tests measure the actual impact of cigarette smoke on a patient’s body. But until these tests go prime time, the pack year is the best we have.

We are currently testing several of these biomarkers and highly recommend any smoker get involved in these clinical studies. Only by learning more about a person’s true risk will we advance the science and continue to take the fight to lung cancer.

‘Til No One Dies of Lung Cancer!