What is the significance of the Fleischer-Peto curve in smoking cessation?

The Fleischer-Peto Curve and Smoking Cessation

The Fleischer-Peto curve demonstrates that mortality risk reduction following smoking cessation occurs gradually over decades, with residual excess risk persisting for 15-25+ years after quitting—far longer than commonly appreciated in clinical practice.

Understanding the Time Course of Risk Reduction

The evidence from large-scale Asian cohort studies reveals a critical reality: former smokers do not return to never-smoker mortality risk levels for an extended period, even after complete cessation 1.

All-Cause Mortality Timeline

• Former smokers who quit <5 years ago show 11% lower mortality compared to current smokers, but remain 38% higher than never smokers (HR 1.38,95% CI 1.28-1.49) 1
• At 10-14 years post-cessation, all-cause mortality remains 25% elevated compared to never smokers (HR 1.25,95% CI 1.13-1.37) 1
• Only after approximately 20 years does all-cause mortality approach never-smoker levels (HR 1.05,95% CI 0.97-1.14) 1, 2

Cardiovascular Disease Mortality

• CVD mortality remains 41% elevated in former smokers who quit <5 years ago (HR 1.41,95% CI 1.16-1.72) 1
• At 10-14 years post-cessation, CVD mortality is still 20% higher than never smokers (HR 1.20,95% CI 1.02-1.41) 1
• CVD risk approaches never-smoker levels after approximately 14 years of abstinence 3

Lung Cancer Mortality: The Most Persistent Risk

Lung cancer mortality demonstrates the most prolonged elevation, particularly in heavy smokers 1:

• Former smokers quitting <5 years ago have 3.51-fold elevated lung cancer mortality compared to never smokers (HR 3.51,95% CI 2.75-4.48) 1
• At 15-19 years post-cessation, lung cancer mortality remains nearly 2-fold elevated (HR 1.97,95% CI 1.41-2.73) 1
• For heavy smokers (>20 pack-years), lung cancer mortality remains 2.20-fold elevated even after 25+ years of cessation 3, 2

Clinical Implications: Current Guidelines Underestimate Residual Risk

The adverse effects of tobacco smoking persist beyond the time windows defined in current clinical guidelines 1:

• USPSTF lung cancer screening guidelines recommend screening only for those who quit within the past 15 years 1
• CVD risk assessment tools typically consider former smokers equivalent to never smokers after just 5 years 1
• These thresholds substantially underestimate the persistent excess mortality risk demonstrated in the Fleischer-Peto curve pattern 1, 3

Dose-Response Relationship: Heavy Smoking Amplifies Duration of Risk

The 20 pack-year threshold represents a critical inflection point 3, 2:

• Former smokers with >20 pack-years have 3.06-fold increased lung cancer mortality compared to never smokers (HR 3.06,95% CI 2.58-3.64) 3
• Current smokers with >20 pack-years have 5.72-fold increased lung cancer mortality (HR 5.72,95% CI 4.73-6.92) 3
• Even 25 years after quitting, former heavy smokers maintain 2.20-fold elevated lung cancer mortality 3, 2

Benefits of Cessation: Earlier is Better, But Late Quitting Still Helps

Despite prolonged residual risk, cessation at any age provides measurable mortality benefit 4:

• Quitting before age 40 avoids approximately 90-95% of excess mortality risk within 3 years 4
• Quitting at ages 40-49 avoids 61-81% of excess risk 4
• Quitting at ages 50-59 still avoids 54-63% of excess risk 4
• Cessation for <3 years potentially averts 5 years of life lost; cessation for 10+ years averts approximately 10 years of life lost 4

Common Pitfalls in Clinical Practice

Do not assume former smokers have returned to baseline risk after short cessation periods 1:

• The 5-year threshold used in many CVD risk calculators significantly underestimates ongoing risk 1
• The 15-year threshold for lung cancer screening eligibility may miss high-risk former heavy smokers 1
• Former smokers with >20 pack-year histories warrant continued surveillance and aggressive risk factor modification for 20-25+ years post-cessation 3, 2

Optimizing Cessation Success

Pharmacotherapy-assisted reduction significantly improves quit rates 1:

• Fast-acting NRT or varenicline as reduction aids increase cessation success (RR 1.68,95% CI 1.09-2.58) 5
• Counseling combined with pharmacotherapy provides additive benefit (OR 1.44,95% CI 1.22-1.70) 6
• Financial incentives increase quit rates (OR 1.46,95% CI 1.15-1.85) 6

Recent quitters demonstrate intermediate outcomes between current smokers and long-term former smokers, confirming immediate benefit despite persistent residual risk 1.