Outcomes of neoadjuvant chemoradiotherapy for locally advanced rectal cancer under non‑smoking conditions confirmed by measuring expiratory CO levels: An observational study

The outcomes of neoadjuvant chemoradiotherapy (CRT) under non-smoking conditions in patients with locally advanced rectal cancer (LARC) remain unclear. The aim of the present study was to evaluate the outcomes in patients with LARC who underwent neoadjuvant CRT under non-smoking conditions, followed by total mesorectal excision (TME). To this end, the medical records of 28 patients treated with CRT and surgery for LARC between January 2014 and December 2019 were retrospectively analyzed. Smoking cessation was monitored by measuring carbon monoxide (CO) levels using a Smokerlyzer. Survival outcomes and clinicopathological factors associated with pathological complete response (pCR) were investigated. The median age was 66 (45-89) years, and 20 (71.4%) patients were male. A total of 16 (57.1%) patients were diagnosed with clinical stage III LARC. Seven patients smoked at diagnosis, with an average expiratory CO level of 8 (8-30) ppm. These patients ceased smoking and maintained exhaled CO levels <3 ppm before treatment. All patients successfully underwent CRT and TME. No major postoperative complications occurred. pCR was achieved in 8/28 patients (28.6%) and the 5-year recurrence-free and overall survival rates were 78.0% [95% confidence interval (CI), 57.4-89.5] and 85.7% (95% CI, 66.3-94.4), respectively. The median follow-up period was 60.1 (range, 5.6-114.6) months. Survival did not significantly differ between smokers and non-smokers at diagnosis. Clinically negative N stage (hazard ratio: 18.9; 95% CI, 1.63-218; P=0.0187) was significantly associated with pCR. In conclusion, neoadjuvant CRT under non-smoking conditions, as confirmed by measuring expiratory CO levels, followed by TME yields favorable pCR rates and survival outcomes in patients with LARC.