Table 1.

Designs and Methods in the PLCO Cancer Screening Trial and the NLST.^*

Variable	PLCO Cancer Screening Trial	NLST
Intervention group	Posteroanterior chest radiography in 77,445 persons	Low-dose CT in 26,722 persons
Control group	Regular care in 77,456 persons	Posteroanterior chest radiography in 26,732 persons
Total no. of participants	154,901	53,454
No. of study sites	10 centers	33 centers
Eligibility criteria
Age	55–74 yr	55–74 yr
Smoking status	Any	≥30 pack-yr; quit time <15 yr before enrollment
Exclusion criteria	History of prostate, lung, colorectal, or ovarian cancer; current cancer treatment; removal of one lung	Previous diagnosis of lung cancer; chest radiography within 1.5 yr before enrollment; hemoptysis, unexplained weight loss of >6.8 kg (15 lb) in the preceding yr
Enrollment period	November 1993–July 2001	August 2002–April 2004
Screening period	November 1993–November 2004	August 2002–September 2007
Follow-up	To year 13 or December 31, 2009, whichever was earlier	To December 31, 2009
Screening schedule	Four screenings: at baseline, year 1, year 2, and year 3 (year 3 screening not given to persons who never smoked after April 1995)	Three screenings: at baseline, year 1, and year 2
Criteria for positivity (abnormal finding that raises clinical suspicion of lung cancer)	Nodule or mass, infiltrate, pleural mass, major atelectasis, noncalcified hilar or mediastinal lymphadenopathy, or major atelectasis12	Noncalcified nodule >4 mm detected on CT, any noncalcified nodule or mass detected on chest radiography
Lung-cancer classification	ICD-O-213	ICD-O-314
References	Prorok et al.,7 Oken et al.,8 and Oken et al.9	Aberle et al.,1 Aberle et al.,10 and Aberle et al.11

^*CT denotes computed tomography, ICD-O-2 International Classification of Diseases for Oncology, 2nd Edition, ICD-O-3 International Classification of Diseases for Oncology, 3rd Edition, NLST National Lung Screening Trial, and PLCO Prostate, Lung, Colorectal, and Ovarian.