It is never too late to stop smoking. Applying working estimates of smoking cessation on five-year overall survival gains after a cancer diagnosis

Background: Detailed data on five-year overall survival (5Y-OS) in relation to smoking cessation after a cancer diagnosis are sparse. Implementation of smoking cessation in cancer treatment centres is also sub-optimal. The aim is to provide working, numeric estimates of 5Y-OS outcomes in relation to quitting smoking to help inform patients with cancer. Methods: 5Y-OS data and hazard ratios (HR) from a moderately sized cohort study from Japan were used to derive survival benefits on Australian cancer survival scenarios ranging from 10 % to 90 % 5Y survival, using standard epidemiological formulas comparing survival in those who recently quit around the time of their cancer diagnosis in comparison to those who continued to smoke. Results: In a scenario of a cancer type with 90 % 5 y survival e.g. breast, prostate cancer, or melanoma, quitting smoking shows a gain in 5Y-OS of 10 %, and a gain in median survival of 2.1 years. In a scenario of 20 % 5 y survival (e.g. lung, liver, brain, or oesophageal cancer) recent quitting shows a 5Y-OS gain of 2 %, and a median survival gain of three months. Conclusion: The greater the survival at presentation, the greater the gain by quitting smoking. Future research should aim to produce estimates based on real-world data.