Effects of cigarette smoking on metabolic activity of lung cancer on baseline 18F-FDG PET/CT

Background. Never-smokers with lung cancer usually have a higher survival rate than that of smokers. The high metabolic activity of lung cancer on F-18-2-Fluoro-2deoxyglucose (F-18-FDG) PET/CT generally indicates a poor outcome. However, there is a lack of reports on the association between cigarette smoking and F-18-FDG metabolic activity in patients with lung cancer. In this study, we aimed to investigate the effects of cigarette smoking on metabolic activity of lung cancer on F-18-FDG PET/CT. Materials and Methods. A total of 338 patients (230 males, 108 females; mean age: 66.3, range 34-86) with pathologically diagnosed lung cancer were enrolled from September 2019 to April 2021. All patients underwent baseline F-18-FDG PET/CT and the maximum standard uptake value (SUVmax) of the primary tumor (pSUVmax), lymph node (nSUVmax) and distant metastasis (mSUVmax) were measured. The associations between cigarette smoking status, clinical stage, pathological subtypes and metabolic parameters on F-18-FDG PET/CT were analyzed. Results. Of the 338 patients, cigarette smoking was identified in 153 patients (45.3%) and the remaining 185 (54.7%) were never-smokers. Smoking was found more frequently in males, squamous cell carcinoma (SCC) and stage III-IV diseases. The pSUVmax in smokers was significantly higher than that in never-smokers (t = 3 .386 , P < 0.001), but the nSUVmax and mSUVmax revealed no statistically significant differences (t = 0.399, P = 0.690 and t = 0.057, P = 0.955; respectively). With the increase of cumulative smoking dose, pSUVmax increased significantly (r = 0.217, P < 0.001). In addition, the pSUVmax in patients with stage III-IV was significantly higher than that in stage I-II (t = 8.509, P < 0.001). Smokers showed a higher pSUVmax than never-smokers for patients with stage I-II (t = 3.106, P = 0.002), but not in stage III-IV (t = 0.493, P = 0 .622) . The pSUVmax was significantly different among patients with different pathological subtypes of lung cancer (F = 11.45, P < 0.001), while only the adenocarcinoma (ADC) and SCC groups showed a difference in pSUVmax (t = 6.667, P < 0.001). Smokers with ADC showed a higher pSUVmax when compared to never-smokers, but not in SCC. There were no significant differences of pSUVmax between smokers and never-smokers at stage I-II ADC or SCC and stage III-IV ADC or SCC. Conclusions. This study demonstrated a close association between cigarette smoking and the metabolic activity of lung cancer and suggests that smoking may be a potential risk factor of higher pSUVmax in early lung cancer on F-18-FDG PET/CT.