Lung Cancer Risk Calculator (PLCOm2012 6-year risk for people who smoke or smoked)

Understanding the lung cancer risk calculator (PLCOm2012) — concept and principle

This calculator uses the PLCOm2012 model to estimate the chance that a person who smokes or used to smoke will be diagnosed with lung cancer within 6 years. Screening programmes use it to decide who benefits most from low-dose CT screening, often with a threshold of 1.51%.

PLCOm2012 log-odds: with the default inputs the result is 1.89% in 6 years (≥ 1.51% screening threshold).

How it is calculated

Log-odds = −4.532506 + 0.0778868 × (age − 62) − 0.0812744 × (education − 4) − 0.0274194 × (BMI − 27) + 0.3553063 × COPD + 0.4589971 × personal cancer history + 0.587185 × family history + 0.2597431 × current smoking − 1.822606 × (10 ÷ cigarettes per day − 0.4021541613) + 0.0317321 × (years smoked − 27) − 0.0308572 × (years since quitting − 10) + race/ethnicity term

Risk = 1 ÷ (1 + e^(−log-odds))

Education runs from 1 (less than high school) to 6 (postgraduate).
Race/ethnicity terms: Black +0.394, Hispanic −0.743, Asian −0.467, Native Hawaiian/Pacific Islander +1.027, White or American Indian/Alaska Native 0.
Pack-years = cigarettes per day ÷ 20 × years smoked.

The principle

The model was fitted in the large US PLCO screening trial. Smoking duration and intensity carry the most weight; the intensity term uses 1 ÷ cigarettes per day because extra cigarettes add less and less risk at high consumption. Age, COPD, family and personal cancer history add risk; higher BMI and education are associated with lower risk. Centring each variable makes the constant the log-odds of a typical participant.

Worked example

Default inputs: age 62, Asian, high-school graduate, BMI 24, no COPD or cancer history, current smoker, 20 a day for 40 years.

Terms: education +0.163, BMI +0.082, current smoking +0.260, intensity −1.823 × (0.5 − 0.402) = −0.178, duration +0.413, quit time −0.031 × (0 − 10) = +0.309, Asian −0.467.
Log-odds = −4.533 + 0.163 + 0.082 + 0.260 − 0.178 + 0.413 + 0.309 − 0.467 = −3.952.
Risk = 1 ÷ (1 + e^3.952) = 1.89%; pack-years = 40.
1.89% ≥ 1.51% → Yes.

Each point is the calculator re-run with only “Cigarettes per day (average)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Cigarettes per day (average)	6-year lung cancer risk
5	0.12%
10	0.77%
15	1.4%
20	1.89%
25	2.25%
30	2.54%
40	2.94%

How to read the result

Where does your result fall?

A risk at or above 1.51% suggests that screening is likely to bring more benefit than harm, but national programmes use different rules, often based on age and pack-years. Quitting smoking lowers future risk more than any test.

Common mistakes

Using it for people who have never smoked.
Underestimating years smoked by not counting earlier periods.
Treating the result as a diagnosis rather than a screening estimate.

Keep in mind: This is a risk estimate, not a diagnosis or medical advice. Discuss screening with a doctor; any symptoms such as persistent cough or blood in sputum need prompt assessment.

Frequently asked questions

What does a 6-year risk of 2% mean?

About 2 in 100 people with the same profile would be diagnosed with lung cancer within 6 years.

Does the model work outside the US?

It has been validated in several countries, but it was built in North American adults aged 55–74.

Does vaping count?

The model uses cigarette smoking only.

Sources: Tammemägi MC, Katki HA, Hocking WG, et al., "Selection criteria for lung-cancer screening", N Engl J Med 2013;368(8):728–736

Checked 9 Nov 2026. Tammemägi MC, Katki HA, Hocking WG, et al., “Selection criteria for lung-cancer screening”, N Engl J Med 2013;368(8):728–736 — PLCOm2012 coefficients and coding as implemented in the open-source R package resplab/PLCOm2012 (plcom2012.R); the 1.51% six-year threshold is a standard value from later screening studies.

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