Mode of lung cancer detection Adenocarcinoma (n=69) Squamous cell carcinoma (n=47)
Chest X-ray screening*      
n. of pts 25 16  
Median TVDT, days 109 80 0.0347
(IQR) (91-185) (56-108)  
n. of pts 44 31  
Median TVDT, days 227 95 0.0108
(IQR) (108-349) (64-230)  
P° (screening vs. incidental) 0.0099 0.2128  
^TVDT calculated according to Schwartz formula [194] after comparison of two consecutive chest X-rays or CT-scans.
°Mann-Whitney test
*Annual repeat screen during population-based chest X-ray screening programme carried out in the Province of Varese, Italy in 1997-2011 [195].
**Asymptomatic subjects with incidental NSCLC detection, for whom previous imaging study was available for tumor size comparisons.
TVDT: Tumor Volume Doubling Time; IQR: Interquartile Range (25%-75%).
Table 1: Median tumor volume doubling time (TVDT)^ of 116 non-small cell lung cancers (NSCLC) by histology and by mode of detection (case series 1997-2011, Center for Thoracic Surgery, University of Insubria).