Smoking accounts for approximately 30% of total cancer deaths each year. Even though former studies show that persons with a cancer diagnosis are less likely to smoke than the general population up to 50% of people who smoke and have lung cancer do not stop smoking after their diagnosis or frequently relapse after smoking cessation. Continued smoking leads to increased all-cause mortality, increased cancer-specific mortality, and decreased quality of life. It is well-known that cancer patients are interested in smoking cessation therefore smoking cessation interventions play an important role in the management of people with cancer.

This study will evaluate the effectiveness of an intensive smoking cessation interventions on cancer patients in real life. The project provides new knowledge about smokers diagnosed with cancer.

This prospective register-based cohort study including smokers attending an intensive smoking cessation intervention (the Gold Standard Programme (GSP)) from 2006-2017 in Denmark. The GSP is a manualised, patient education programme taught by specially trained staff, including pharmacologic strategies.

Inclusion Criteria:

• Smokers registered in the National Danish Smoking Cessation Database between January 2006 until May 2017

Exclusion Criteria:

• Entries referring to smokers attending more than one smoking cessation intervention (the latest entry will be used)
• Smokers younger than 18 years of age
• Smokers attending interventions other than the intensive Gold Standard Programme for smoking cessation (GSP)
• Smokers where the smoking cessation unit pre-decided not to follow up on their participants
• Smokers in the non-cancer group diagnosed with benign neoplasms, tumours of unknown etymology or non-melanoma skin cancer (ICD-10 diagnoses: D30.1-9; D32-33; D35.2-4; D41.1-9; D44.3-5; C44, C46.0)

The population in this study are smokers in Denmark, with or without cancer, who are motivated to attempt to quit smoking, and have attented an intensive smoking cessation programme.