Quitting smoking after a cancer diagnosis remains beneficial

In its eighth report summarizing the evidence, the International Agency for Research on Cancer (IARC) emphasizes that quitting smoking after a cancer diagnosis can significantly improve survival and reduce the risk of disease progression. This report will be presented at the Union for International Cancer Control (UICC) World Cancer Congress, to be held in Hong Kong on September 25, 2026.

Smoking is responsible for approximately one-quarter of cancer deaths worldwide. While the benefits of quitting smoking to prevent cancer are widely established, a misconception persists: once cancer is diagnosed, quitting smoking no longer significantly improves the situation. However, according to the IARC, data available over the past decade show that quitting smoking after a cancer diagnosis can be associated with improved survival.[1].

In support of its report, the IARC participated in two cohort studies and one modelling study, the main findings of which it presents.

A study on the benefits of quitting smoking after a lung cancer diagnosis

A study conducted jointly by the IARC and the NN Blokhin National Research Center for Oncology in Russia followed 517 people for several years who had just been diagnosed with stage IA to IIIA non-small cell lung cancer. These individuals were still smoking at the time of diagnosis. Among them, 220 (42 with %) quit smoking during the follow-up period, including 80 with % within three months of diagnosis.

People who quit smoking lived an average of 22 months longer than those who continued to smoke. Five years after diagnosis, overall survival reached 60.6 µg/L in those who quit, compared to 48.6 µg/L in those who continued. Progression-free survival was 54.4 µg/L and 43.8 µg/L, respectively. After adjusting for several factors, smoking cessation was associated with a 33 µg/L reduction in the risk of death from all causes, a 25 µg/L reduction in the risk of cancer-related death, and a 30 µg/L reduction in the risk of disease progression compared to smokers. Benefits were observed in patients with both early-stage and more advanced cancers, as well as in smokers with different smoking histories.

Similar results were observed for kidney cancer.

A second study involved 212 people with renal cell carcinoma who were smoking at the time of diagnosis. They were followed for an average of eight years. During this period, 84 people, or 40 %, quit smoking, again primarily within three months of diagnosis.

At three years, the death rate was 6 µt/µt in those who quit smoking, compared to 24 µt/µt in those who continued. At five years, these rates were 15 µt/µt and 40 µt/µt, respectively. After adjusting for various patient, cancer, and treatment characteristics, smoking cessation was associated with a 50 µt/µt reduction in the risk of all-cause mortality, a 46 µt/µt reduction in the risk of cancer-related death, and a 55 µt/µt reduction in the risk of disease progression compared to smokers. Survival benefits were observed at all cancer stages, including in patients with stage IV cancer.

Integrating smoking cessation into cancer care

Beyond clinical outcomes, the IARC also presents data on the economic benefits of integrating smoking cessation support into cancer care. An analysis conducted from the perspective of the UK's National Health Service (NHS) assessed the cost-effectiveness of providing support at the time of cancer diagnosis. According to this analysis, the additional costs associated with achieving a quality-adjusted life year (QALY) were estimated to range from £2,606 (€3,030) for lung cancer to £5,495 (€6,390) for head and neck cancers. These amounts were below the threshold of £20,000 (€23,000) per QALY typically used in this analysis as a benchmark for determining whether an intervention is cost-effective. The direct integration of smoking cessation support into care pathways was also associated with a net monetary benefit compared to simply referring patients to an external service: this was estimated at £1,543 (€1,794) per lung cancer patient and £5,362 (€6,235) per kidney cancer patient. Across the NHS, systematic integration of smoking cessation services into cancer care pathways was estimated to generate approximately £88 million (€102 million) in savings per year.

Based on these findings, the IARC believes that smoking cessation support should be integrated into the care of people with cancer, rather than offered solely as a referral to external services. The agency recommends that healthcare professionals assess the tobacco use of all cancer patients at every clinical visit and then offer smoking cessation support regardless of the type or stage of the disease. It also calls on public authorities to provide long-term funding for tobacco addiction treatment programs and to guarantee free or subsidized access to pharmacological smoking cessation treatments.

The IARC also recommends integrating tobacco addiction treatment into national guidelines and quality standards in oncology, as well as strengthening the training of oncology professionals. Patient organizations are also encouraged to inform people with cancer and their families about the benefits of quitting smoking, particularly regarding treatment outcomes, progress in treatment, and prevention of cancer recurrence.

In its public policy recommendations, the agency advocates, in particular, developing smoking cessation interventions directly within cancer care facilities, including in pre-operative pathways; reducing financial and geographical barriers to accessing treatments and advice; and implementing indicators to monitor the use of these services, their quality, and their outcomes. It also emphasizes the importance of psychosocial support tailored to the specific difficulties faced by people with cancer, including stress, guilt, and fear.

The IARC emphasizes, however, that this is a synthesis of research and not a systematic review of all available data. The results presented should therefore be interpreted within the context of the original studies on which they are based.

©Generation Without Tobacco

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[1]Tobacco cessation after cancer diagnosis: a fundamental component of cancer care, IARC Evidence Summary Briefs, No. 8, Lyon, France: International Agency for Research on Cancer, published on September 23, 2026, accessed on September 24, 2026

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