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20th January 2022
Smoking cessation at the time of a lung cancer diagnosis is linked to an improved survival from both non-small and small cell lung cancer, according to the findings of a systematic review by a team from the Institute for Cancer Research, Prevention and Clinical Network, Florence, Italy
Data from the World Health Organization shows that in 2020, globally, there were 2.21 million cases of lung cancer and which led to 1.8 million deaths. In addition, lung cancer has a poor prognosis and Cancer Research UK suggests that only around 15% of those with lung cancer will survive for 5 years or more after diagnosis. Cigarette smoking is a major factor in the development of lung cancer, with one analysis of the burden of respiratory tract cancers indicating that smoking contributed to an estimated 64·2% of all deaths from tracheal, bronchus, and lung cancer and 63·4% of all deaths from larynx cancer in 2019.
Although one study with 517 smokers, found that smoking cessation at the time of a lung cancer diagnosis can reduce the risk of future lung cancer, for the present study, the Italian team sought to provide a more robust estimate of the overall prognostic value of smoking cessation at or around the time of a lung cancer diagnosis. They searched for articles which included those who continued to smoke and those who quit in relation to their cancer diagnosis and the associated changes in survival. The team calculated relative risks for the association between smoking cessation and the survival from lung cancer.
A total of 21 studies were included in the systematic review with patients diagnosed with non-small cell lung cancer (10 studies, 5315 patients) and small cell lung cancer (5 studies, 1133 patients), together with a further six studies of both cancer subtypes or where the subtype was not specified. The mean age of lung cancer diagnosis across the studies ranged from 60 to 70 years and the proportion of men ranged from 40.2% to 91.8%. The duration of follow-up also ranged from 12 months to 27.7 years.
Smoking cessation at or around the time of diagnosis was associated with a better overall survival regardless of lung cancer type. For smoking cessation at any time, compared to those who continued smoking (used as the reference group), the relative risk for non-small cell lung cancer was 0.77 (relative risk, RR = 0.77, 95% CI 0.66 – 0.90) and this reduction was broadly similar compared to those stopping strictly at or after their diagnosis or up to 12 months before the diagnosis. For small cell lung cancer, overall survival was also broadly similar (RR = 0.75, 95% CI 0.57 – 0.99). Even in studies where the cancer subtype was not specified, there were survival benefits among quitters (RR = 0.81, 95% CI 0.68 – 0.96).
The authors calculated an overall benefit for those who undertook smoking cessation at or around the time of their lung cancer diagnosis, finding that such individuals had a 29% improvement in their overall survival compared to those who continued to smoke (RR = 0.71, 95% CI 0.64 – 80).
The authors concluded that advice to quit smoking at or around the time of a lung cancer diagnosis, should arguably become a non-optional part of the management of these patients.
Caini S et al. Quitting smoking at or around diagnosis improves the overall survival of lung cancer patients: a systematic review and meta-analysis J Thorac Oncol 2022
6th September 2021
Smoking is a risk factor for cardiovascular disease (CVD) and responsible for 1 of every 4 CVD deaths although smoking is a very preventable CVD risk factor. In one observational study of over 8,000 former heavy (i.e., more than 20 cigarettes/day) it was found that within 5 years of cessation, there was a 39% reduced risk of CVD among those who quit, compared to current smokers. Other evidence indicates a potential dose-response relationship between smoking and ischaemic stroke, such that any reduction is beneficial. However, while a meta-analysis has found that reduced use of cigarettes decreases the risk of lung cancer, the impact on CVD was less clear. This led a team from the Department of Family Medicine/Supportive Care Centre, Seoul, Korea, to compare the effect of either smoking cessation or reduction on the risk of cardiovascular disease outcomes. The team used a Korean national health database and collected information of individuals over 40 years of age who had undergone two health examinations in 2009 and again in 2011 to determine any changes in smoking behaviour. A smaller subgroup who had undergone a third examination in 2013 were also included. The team focused on a group of current smokers and excluded those with prior CVD or cancer and used information on smoking status obtained from a biennial national health examination self-administered questionnaire. Individuals were classed as heavy smokers (> 20 cigarettes/day), moderate smokers (10 – 19/day) and light smokers (< 10/day). Compared with the first examination in 2009, participants were then categorised as quitters, reducers I (> 50% reduction), reducers II (20 – 50% reduction), sustainers (reduced by < 20%) and increasers (>20% in smoking). The primary endpoints for the study were newly diagnosed stroke and myocardial infarction (MI) and secondary endpoints included overall mortality, fatal strokes and fatal Mis. Many other health parameters were collected included age, sex, body mass index, duration of smoking, alcohol consumption, levels of exercise, co-morbidities, all of which were adjusted for in the analyses.
A total of 897,975 current smokers with a mean age of 53 years (94.5% male) were followed over 6.2 years. There were a total of 17,748 strokes and 11,271 MI events during the follow-up period. Among smokers, 52.8% were classed as heavy, 37.3% as moderate and the remainder as light during their first examination. Among smoking quitters, there was a significantly reduced risk of stroke (adjusted Hazard ratio, aHR = 0.77, 95% CI 0.74 – 0.81) and MI (aHR = 0.74) compared to sustainers. In addition, smoking cessation was also associated with a significant reduction in all-cause mortality (aHR = 0.92, 95% CI 0.89 – 0.94). However, among reducers I and II, the risk of both stroke and MI were not significantly lower. For example, for reducers I, stroke aHR = 1.02 (95% CI 0.97 – 1.08) and MI aHR = 0.99 (95% CI 0.92 – 1.06).
At the third examination in 2013, quitters who had relapsed to either the level of reducer I, II, sustainer or increaser, had a 42 to 66% increased risk of stroke and a 54 – 69% increased risk of MI compared to quitters, depending where they were in terms of their relapsed level of smoking.
The authors concluded that only smoking cessation and not reduction was associated with a reduced risk of adverse cardiovascular outcomes.
Jeong SM et al. Smoking cessation, but not reduction, reduces cardiovascular disease incidence. Eur Heart J 2021