Quitting smoking after cancer diagnosis sharply improves survival, study finds

By Vijay Kumar MalesuReviewed by Susha Cheriyedath, M.Sc.Oct 13 2025

Even in advanced cancer, patients who quit smoking soon after diagnosis lived longer, yet most were never offered meaningful cessation support.

Study: Smoking Cessation and Mortality Risk in Cancer Survivorship: Real-World Data From a National Cancer Institute–Designated Cancer Center. Image Credit: Pixel-Shot / Shutterstock

In a recent study published in the Journal of the National Comprehensive Cancer Network, researchers assessed whether postdiagnosis smoking cessation is associated with overall survival (OS) across cancer stages using electronic health record (EHR) data.

Background

Quitting smoking after a cancer diagnosis is a simple step that can add years to life. Cigarette smoking causes about 30% of cancer deaths and 80% of lung cancer deaths in the United States (US). Stopping at any age lowers excess mortality. In clinics, tobacco use is not continually assessed, and treatment is not consistently offered. Guidelines from the National Comprehensive Cancer Network (NCCN) and the American Society of Clinical Oncology (ASCO) call for routine screening and support. Still, time limits and training gaps can sideline cessation. Further research should clarify how stopping after diagnosis relates to overall survival across stages, including in real-world oncology settings where cessation support may vary.

About the study

This observational cohort included adults with an active cancer diagnosis who attended outpatient oncology clinics within six months of June 1, 2018, at a National Cancer Institute (NCI)-designated Comprehensive Cancer Center. Smoking status was recorded at each visit in EHR using Electronic Health Record-Enabled Evidence-Based Smoking Cessation Treatment (ELEVATE) prompts and was categorized as never, former, or currently smoking; those recently receiving cessation treatment were counted as currently smoking. The index visit was the first encounter near the start of the study. The primary outcome was OS to death from any cause, censored June 30, 2020.

In a secondary analysis among patients who smoked at the index visit, cessation within six months was defined as seven-day self-reported abstinence with a documented quit between January 1 and June 30, 2019. Demographics, cancer type and stage, and years since diagnosis were abstracted from EHR and tumor registry data. Multivariable Cox proportional hazards models estimated adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs). Survival analyses combined Kaplan–Meier curves for visualization with model-based estimates from Cox models to derive adjusted survival probabilities. Analyses used Statistical Analysis System (SAS) version 9.4. Institutional Review Board (IRB) approval covered the analysis of deidentified outcomes from a quality improvement database.

Study results

Among 13,282 patients, 6,568 (49.5%) had never smoked, 4,989 (37.6%) were former smokers, and 1,725 (13.0%) were currently smoking at the index visit. Most were female (60.0%), White (83.0%), and aged 61 years or older (60.0%). Advanced-stage disease was common, with stage III in 4,679 (35.2%) and stage IV in 3,675 (27.7%). Compared with patients who never smoked, mortality risk was higher in those who formerly smoked (aHR 1.13; CI 1.03 to 1.25) and in those who currently smoke (aHR 1.35; CI 1.20 to 1.53). Stage-specific analyses showed a consistent pattern.

Patients who currently smoke had higher all-cause mortality than those who never smoked in stages I and II (aHR 1.37; CI 1.02 to 1.85), stage III (aHR 1.30; CI 1.05 to 1.61), and stage IV (aHR 1.35; CI 1.13 to 1.60). Two-year survival estimates were 81.4% for never smokers, 79.4% for former smokers, and 76.4% for current smokers, with significant differences.

Among the 1,725 patients who smoked at the index visit, 381 (22.1%) quit within six months based on seven-day abstinence and a documented quit status. After adjustment, continued smoking was associated with a higher risk of death than quitting (aHR 1.97; CI 1.53 to 2.55). Estimated adjusted survival favored quitting at one year (91% quit versus 83.9% continued) and two years (85.1% versus 74.7%). In stage-stratified analyses of postdiagnosis change, the association of continued smoking with mortality was strongest in advanced disease. For stages III and IV combined, continued smoking carried a higher risk than quitting (aHR 2.11; CI 1.60 to 2.79); for stages I and II, the estimate was smaller and not statistically significant (aHR 1.30; CI 0.67 to 2.51).

Among 719 patients who underwent cancer-related surgery near the index visit, 118 were smokers; of these, 76 quit and 42 continued. Continued smoking in this subgroup was associated with increased mortality compared with quitting (aHR 4.41; CI 1.22 to 15.87). Across the cohort, current smoking at baseline clustered with male sex, age 70 years or younger, tobacco-related solid tumors, advanced stage, and fewer than five years since diagnosis. Overall, the results indicate that smoking at or after diagnosis is linked to lower OS, while postdiagnosis cessation is linked to improved OS, including in advanced-stage illness.

Study limitations

Smoking status was self-reported and not biochemically verified, potentially underestimating the true benefit of cessation. Treatment data before mid-2018 were limited due to an EHR transition, and unmeasured factors, such as healthier lifestyles or better treatment adherence among quitters, may contribute to survival differences. Outcomes reflected overall survival, not cancer-specific mortality, which may limit causal interpretation. The single-center setting and predominantly White population may also limit generalizability to more diverse cancer populations.

Conclusions

Postdiagnosis smoking cessation was associated with longer OS in cancer survivorship, including in advanced-stage disease. Because only one in five patients quits within six months, low-burden support is needed. EHR ELEVATE and the National Cancer Institute Cancer Center Cessation Initiative (C3I) show how EHR tools expand reach and effectiveness. Embedding counseling, referrals, and pharmacotherapy alongside surgery, radiation therapy, and systemic therapy can make cessation a fourth pillar of cancer care.