Effects of Smoking Cessation
Counseling and Smoking Cessation
Drug Treatment and Smoking Cessation

Note: A separate PDQ summary on Levels of Evidence for Cancer Screening and Prevention Studies ¹ is also available.

The summaries in the Cancer Prevention section of the PDQ refer to cancer prevention, defined as a reduction in the incidence of cancer. The PDQ includes summaries generally classified by histological type of cancer, especially when there are known risk factors for the specific types of cancer. This summary addresses a specific risk factor, tobacco use, which is associated with a large number of different cancers (and other chronic diseases) and unequivocally contains human carcinogens.[1] The focus of the summary is on clinical interventions by health professionals that decrease the use of tobacco.

Based on solid evidence, cigarette smoking causes various cancers, including, but not limited to lung cancer. Smoking avoidance and smoking cessation results in decreased incidence and mortality from cancer.

Description of the Evidence

• Study Design: Evidence obtained from a randomized controlled trial.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: The relative risk (RR) of several cancers is much greater in cigarette smokers compared to nonsmokers (depending on the anatomical site of the cancer and the intensity and duration of smoking, the RR can range from twofold to tenfold or greater in smoking populations). A reduction of 15% is seen in the RR of all-cause mortality in heavy smokers subjected to intensive clinical cessation interventions.
• External Validity: Good.

Based on solid evidence, counseling by a health professional improves smoking cessation rates (as does simple advice from a physician to stop smoking).

Description of the Evidence

• Study Design: Evidence obtained from randomized controlled trials.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: Counseling improves cessation rates (physician advice: odds ratio [OR], 1.74; 95% confidence interval [CI], 1.48–2.05).[2]
• External Validity: Good.

Based on solid evidence, drug treatments, including nicotine replacement therapies (gum, patch, spray, lozenge, and inhaler), antidepressant therapy (e.g., bupropion), and nicotinic receptor agonist therapy (varenicline), result in better smoking cessation rates than placebo.

Description of the Evidence

• Study Design: Evidence obtained from randomized controlled trials.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: Treatments, alone or in combination, improve cessation rates over placebo after 6 months (OR, 1.77; 95% CI, 1.66–1.88).[3]
• External Validity: Good.

References

1. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans.: Tobacco smoke and involuntary smoking. IARC Monogr Eval Carcinog Risks Hum 83: 1-1438, 2004.  [PUBMED Abstract]
   
   
2. Lancaster T, Stead L: Physician advice for smoking cessation. Cochrane Database Syst Rev (4): CD000165, 2004.  [PUBMED Abstract]
   
   
3. Silagy C, Lancaster T, Stead L, et al.: Nicotine replacement therapy for smoking cessation. Cochrane Database Syst Rev (3): CD000146, 2004.  [PUBMED Abstract]