Response to Safiri et al. “Comments on Potential Impact of Including Time to First Cigarette in Risk Models for Selecting Ever-Smokers for Lung Cancer Screening”
Authors: Fangyi Gu, Li Cheung, Hormuzd Katki, Neil Caporaso
Journal: Journal of Thoracic Oncology (2017)

We agree with Safiri et al.1Safiri S. Mansourpour H. Ayubi E. Comments on potential impact of including time to first cigarette in risk models for selecting ever-smokers for lung cancer screening.J Thorac Oncol. 2017; 12: e207Abstract Full Text Full Text PDF Scopus (2) Google Scholar that the difference in area under the receiver operating curve is optimistic and that to build a model, an independent data set with time to first cigarette (TTFC) is required. However, our article2Gu F, Cheung LC, Freedman ND, Katki HA, Caporaso NE. Potential impact of including time to first cigarette in risk models for selecting ever-smokers for lung cancer screening [e-pub ahead of print]. J Thorac Oncol. https://doi.org/10.1016/j.jtho.2017.08.001, accessed.Google Scholar aimed to assess the potential added value of TTFC to risk-based screening, as can be seen clearly in the title and the abstract objective. The word potential in the title accurately represents the preliminary nature of the article rather than a formal model building. This intent is also clearly stated in the “Discussion” section, in which we stated that “further studies in a no-screening population would be ideal to build a model used for risk prediction.”2Gu F, Cheung LC, Freedman ND, Katki HA, Caporaso NE. Potential impact of including time to first cigarette in risk models for selecting ever-smokers for lung cancer screening [e-pub ahead of print]. J Thorac Oncol. https://doi.org/10.1016/j.jtho.2017.08.001, accessed.Google Scholar In terms of public health relevance, area under the receiver operating curve is not a good assessment tool. In this regard, we conducted another type of analysis, as presented in Table 3 and Table 4,2Gu F, Cheung LC, Freedman ND, Katki HA, Caporaso NE. Potential impact of including time to first cigarette in risk models for selecting ever-smokers for lung cancer screening [e-pub ahead of print]. J Thorac Oncol. https://doi.org/10.1016/j.jtho.2017.08.001, accessed.Google Scholar to assess the potential public health relevance. In the “Discussion” section, we stated, “From a public health perspective, in relative terms the percentages who benefited from adding TTFC are small (2.00% and 1.72%), but the absolute number of persons in the potential U.S. screening population of 9 million who might benefit cannot be ignored.”2Gu F, Cheung LC, Freedman ND, Katki HA, Caporaso NE. Potential impact of including time to first cigarette in risk models for selecting ever-smokers for lung cancer screening [e-pub ahead of print]. J Thorac Oncol. https://doi.org/10.1016/j.jtho.2017.08.001, accessed.Google Scholar Potential Impact of Including Time to First Cigarette in Risk Models for Selecting Ever-Smokers for Lung Cancer ScreeningJournal of Thoracic OncologyVol. 12Issue 11PreviewSelecting individuals on the basis of model-predicted risks has been reported to improve lung cancer screening efficiency. On the basis of case-control studies, time to first cigarette (TTFC), a nicotine dependency measurement, has been a strong independent predictor of lung cancer risk. Our objective was to verify the TTFC–lung cancer association in the prospective National Lung Screening Trial and evaluate whether adding TTFC can improve lung cancer risk-prediction models. Full-Text PDF Open AccessComments on Potential Impact of Including Time to First Cigarette in Risk Models for Selecting Ever-Smokers For Lung Cancer ScreeningJournal of Thoracic OncologyVol. 12Issue 12PreviewWe read with great interest the article “Potential Impact of Including Time to First Cigarette in Risk Models for Selecting Ever-Smokers for Lung Cancer Screening” by Gu et al.,1 which has great clinical significance in lung cancer screening. The study demonstrated that adding time to first cigarette (TTFC) to the lung cancer incidence model increases the area under the receiver operating curve (AUC) from 0.6862 to 0.6941 (difference in AUC 0.0079), whereas the improvement in AUC was not statistically significant if TTFC was to be added to the lung cancer death model. Full-Text PDF Open Archive