The effects of continued smoking in head and neck cancer patients treated with radiotherapy: A systematic review and meta-analysis

Purpose To determine the effects of continued smoking in head and neck cancer (HNC) patients undergoing radiotherapy on overall survival (OS), locoregional control (LRC), quality of life (QoL) and acute and late toxicities. Methods Articles from January 1990 to August 14, 2018 were searched in PubMed, MEDLINE (Ovid), Embase, Scopus, The Cochrane Library, CINAHL and AUSThealth. Articles were included if majority of patients were treated with radiotherapy and smokers were defined as those who continued to smoke during or after radiotherapy. Data extraction and risk of bias assessment was performed by three independent co-authors using summary data of original studies. A meta-analysis using a random effects model was conducted for OS and LRC. In addition, a qualitative synthesis was performed for toxicities and quality of life as only a limited number of articles were available. Results The initial search identified 2217 studies, with 24 articles comprising 6332 patients eligible for inclusion. Analysis demonstrated that continued smoking was associated with approximately two times the risk of mortality (RR = 1.85, 95% CI 1.55–2.21, p < 0.0001, I2 = 43%) in HNC patients. Similarly, the risk of locoregional failure was more than two times greater in HNC patients who continued smoking (RR = 2.24, CI 1.42–3.52, p = 0.0005, I2 = 64%). The qualitative synthesis indicates that continued smoking may contribute to an elevated incidence of late but not acute toxicities. Conclusions This review provides evidence that continued smoking is associated with a lower OS and LRC and a higher incidence of late toxicities. Therefore, clinicians should strongly encourage smoking cessation amongst all head and neck cancer patients.