Smoking cessation after a cancer diagnosis: Commentary on special supplement in Cancer Epidemiology

Smoking by cancer patients and survivors increases overall mortality, cancer related mortality risk for second primary cancer, and smoking cessation after a cancer diagnosis has been shown to improve survival [12] . Consequently, smoking cessation is considered an important element of quality cancer care and has been endorsed by organisations across multiple countries including the American Society of Clinical Oncology [3] , American Association for Cancer Research [4] , International Association for the Study of Lung Cancer [5] and the Clinical Oncology Society of Australia [6] . Despite promising international efforts to improve rates of smoking cessation, up to 50 % of cancer survivors who were smoking at diagnosis continue to smoke [7] . Many research gaps remain within the literature and uptake of smoking cessation programs worldwide has remained relatively poor. To address these gaps, Cancer Epidemiology issued a call for papers in February 2021 for a special edition on tobacco cessation after a cancer diagnosis. Studies were received predominantly from the USA, Australia, and Canada, with topics ranging from the assessment of smoking status, rates of smoking use and cessation (including e-cigarette use), the effects of continued smoking on treatment outcomes and policies and programs that have been implemented to address smoking cessation amongst patients with cancer.

Although smoking by cancer patients is known to cause adverse cancer treatment outcomes, there remains sparse literature on the effects of how smoking cessation after a cancer diagnosis can affect clinical outcomes. This special issue included a systematic review and meta-analysis by Phua et al., demonstrating that patients with tobacco related tumours who are currently and formerly smoking at baseline are more likely to develop a second primary tumour when compared to those who never smoked [8] . The authors highlighted that an analysis on continued smoking was limited by the small number of articles investigating this, demonstrating the need for more studies to record whether patients are continuing or ceased smoking post diagnosis. Kokts-Porietis et al. (USA) investigated the effects of smoking status (pre and post diagnosis) of endometrial cancer (a non-tobacco related tumour) and found that a more extensive smoking history was associated with reduced survival [9] . There is a need for more accurate quantification from large studies on the effects of continued smoking and recent quitting, especially for non-tobacco related tumours where there is currently limited evidence.