Smoking cessation at the time of a lung cancer diagnosis is linked to an improved survival from both non-small call and small cell types (NSCLC and SCLC, respectively), 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, which led to 1.8 million deaths. In addition, it has a poor prognosis and Cancer Research UK suggests that only around 15% will survive for five 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 cancers 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 disease, 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 survival.

Smoking cessation at lung cancer diagnosis

A total of 21 studies were included in the systematic review with patients diagnosed with NSCLC (10 studies, 5315 patients) and SCLC (five 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 NSCLC 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 SCLC, 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 should arguably become a non-optional part of the management of these patients.

Citation
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.