Purpose: Breast cancer is the most prevalent malignancy among women worldwide. Smoking increases the risk of breast cancer and is associated with poorer treatment outcomes. Although smoking behaviour and cessation have been studied among breast cancer patients, the existing evidence remains heterogeneous, and the timing of cessation around diagnosis is not fully understood. The aim of this study was to determine the proportion of breast cancer patients who quit smoking after diagnosis and to identify factors associated with smoking cessation.

Methods: In this retrospective study, the smoking status of 6456 consecutive breast cancer patients from years 2010 to 2022 was evaluated. All patients were requested to complete a baseline questionnaire including information on their smoking status. The follow-up information was collected from the patient records.

Results: At the time of diagnosis, 851 patients (13.2%) were actively smoking. Follow-up data were available for 736 patients (86.5%), of whom 189 (25.7%) quit smoking at the time of diagnosis despite the absence of a formal cessation program. Nearly half (44.7%) of all smoking cessation events occurring within the 5-year period before and after diagnosis took place within the year of diagnosis. Smoking cessation was significantly more likely at the time of diagnosis than during subsequent years.

Conclusion: Cancer diagnosis provides a timely opportunity for smoking cessation and highlights the potential value of integrating smoking cessation interventions at the time of diagnosis.

Keywords: Breast cancer; Health behaviour; Retrospective study; Smoking cessation; Smoking, tobacco.