Monitoring expiratory carbon monoxide to study the effect of complete smoking cessation on definitive radiation therapy for early stage glottic carcinoma

Previous studies reported that cigarette smoking during radiation therapy was associated with unfavorable outcomes in various cancers using medical interviewing or monitoring of cotinine. Here, we evaluated the effect of smoking cessation on definitive radiation therapy for early stage glottic carcinoma by monitoring expiratory carbon monoxide (CO). We enrolled 103 patients with early glottic carcinoma (T1N0/T2N0 = 79/24) who underwent conventional radiotherapy between 2005 and 2016. The median age was 70 years. Pathologically, all patients had squamous cell carcinoma. Since 2009, we confirmed smoking cessation before radiation therapy by medical interviews. Since 2014, we measured expiratory CO to strictly monitor smoking cessation. The patients were divided according to diagnosis years: ‘no cessation’ (2005–2008), ‘incomplete cessation’ (2009–2013), and ‘complete cessation’ (2014–2016). We retrospectively analyzed the local recurrence rate and disease-free survival (DFS). The median follow-up period was 60.1 months (range, 1.9–110.0 months). The 2-year local recurrence rate in the ‘complete cessation’ group was 5.3% and tended to be lower than that in the ‘incomplete cessation’ group (13.7%) and ‘no cessation’ group (21.2%). Multivariate analysis revealed that ‘no cessation’ was a risk factor for DFS (hazard ratio [HR] = 4.25) and local recurrence rate (HR = 16.5, <i>p</i> We confirmed that the ‘complete cessation’ group had better prognosis than the ‘no cessation’ group by monitoring expiratory CO during radiation therapy for early stage glottic carcinoma. Moreover, monitoring expiratory CO was easier and more suitable than conventional methods for evaluating smoking cessation because it provided real-time measurements.

既往研究通过医学访谈或可替宁（cotinine）监测手段，证实放疗期间吸烟与多种癌症的不良预后存在关联。本研究通过监测呼出气一氧化碳（expiratory carbon monoxide, CO），评估戒烟对早期声门癌根治性放疗的影响。本研究纳入2005年至2016年间接受常规放疗的103例早期声门癌患者，其中T1N0型79例、T2N0型24例；患者中位年龄为70岁，病理分型均为鳞状细胞癌。2009年起，研究团队通过医学访谈确认患者放疗前的戒烟情况；2014年起，则通过测量呼出气一氧化碳严格监测患者的戒烟状态。研究人员按诊断年份将患者分为三组：“未戒烟组”（2005–2008年）、“戒烟不完全组”（2009–2013年）及“完全戒烟组”（2014–2016年）。本研究对局部复发率与无病生存期（disease-free survival, DFS）进行了回顾性分析，患者中位随访时间为60.1个月（范围1.9–110.0个月）。完全戒烟组的2年局部复发率为5.3%，低于戒烟不完全组（13.7%）与未戒烟组（21.2%）。多因素分析结果显示，未戒烟状态是无病生存期（风险比[HR]=4.25）与局部复发率（HR=16.5，*p*）的危险因素。本研究证实，在早期声门癌的放疗过程中通过呼出气一氧化碳监测，完全戒烟组患者的预后优于未戒烟组；此外，相较于传统评估方法，呼出气一氧化碳监测可提供实时检测结果，操作更简便，更适用于戒烟情况的评估。