title: Lung cancer screening in the randomized Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial.
abstract: BACKGROUND
  The 5-year overall survival rate of lung cancer patients is approximately 15%. Most patients are diagnosed with advanced-stage disease and have shorter survival rates than patients with early-stage disease. Although screening for lung cancer has the potential to increase early diagnosis, it has not been shown to reduce lung cancer mortality rates. In 1993, the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial was initiated specifically to determine whether screening would reduce mortality rates from PLCO cancers.
  
  
  METHODS
  A total of 77 464 participants, aged 55-74 years, were randomly assigned to the intervention arm of the PLCO Cancer Screening Trial between November 8, 1993, and July 2, 2001. Participants received a baseline chest radiograph (CXR), followed by three annual single-view CXRs at the 10 US screening centers. Cancers were classified as screen detected and nonscreen detected (interval or never screened) and according to tumor histology. The positivity rates of screen-detected cancers and positive predictive values (PPVs) were calculated. Because 51.6% of the participants were current or former smokers, logistic regression analysis was performed to control for smoking status. All statistical tests were two-sided.
  
  
  RESULTS
  Compliance with screening decreased from 86.6% at baseline to 78.9% at the last screening. Overall positivity rates were 8.9% at baseline and 6.6%-7.1% at subsequent screenings; positivity rates increased modestly with smoking risk categories (P(trend) < .001). The PPVs for all participants were 2.0% at baseline and 1.1%, 1.5%, and 2.4% at years 1, 2, and 3, respectively; PPVs in current smokers were 5.9% at baseline and 3.3%, 4.2%, and 5.6% at years 1, 2, and 3, respectively. A total of 564 lung cancers were diagnosed, of which 306 (54%) were screen-detected cancers and 87% were non-small cell lung cancers. Among non-small cell lung cancers, 59.6% of screen-detected cancers and 33.3% of interval cancers were early (I-II) stage.
  
  
  CONCLUSIONS
  The PLCO Cancer Screening Trial demonstrated the ability to recruit, retain, and screen a large population over multiple years at multiple centers. A higher proportion of screen-detected lung cancers were early stage, but a conclusion on the effectiveness of CXR screening must await final PLCO results, which are anticipated at the end of 2015.
authors.affiliation: Department of Clinical Oncology, Marshfield Clinic, 1000 North Oak Avenue, Marshfield, WI 54449, USA. hocking.william@marshfieldclinic.org
authors.forename: William G
authors.initials: WG
authors.lastname: Hocking
authors.forename: Ping
authors.initials: P
authors.lastname: Hu
authors.forename: Martin M
authors.initials: MM
authors.lastname: Oken
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Winslow
authors.forename: Paul A
authors.initials: PA
authors.lastname: Kvale
authors.forename: Philip C
authors.initials: PC
authors.lastname: Prorok
authors.forename: Lawrence R
authors.initials: LR
authors.lastname: Ragard
authors.forename: John
authors.initials: J
authors.lastname: Commins
authors.forename: David A
authors.initials: DA
authors.lastname: Lynch
authors.forename: Gerald L
authors.initials: GL
authors.lastname: Andriole
authors.forename: Saundra S
authors.initials: SS
authors.lastname: Buys
authors.forename: Mona N
authors.initials: MN
authors.lastname: Fouad
authors.forename: Carl R
authors.initials: CR
authors.lastname: Fuhrman
authors.forename: Claudine
authors.initials: C
authors.lastname: Isaacs
authors.forename: Lance A
authors.initials: LA
authors.lastname: Yokochi
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Riley
authors.forename: Paul F
authors.initials: PF
authors.lastname: Pinsky
authors.forename: John K
authors.initials: JK
authors.lastname: Gohagan
authors.forename: Christine D
authors.initials: CD
authors.lastname: Berg
mesh_terms: D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000473:pathology; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000401:mortality; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D016015:Logistic Models; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000473:pathology; D008297:Male; D008400:Mass Chest X-Ray; D008875:Middle Aged; D009367:Neoplasm Staging; D010051:Ovarian Neoplasms / Q000175:diagnosis / Q000401:mortality; D010349:Patient Compliance; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000401:mortality; D012907:Smoking / Q000009:adverse effects; D014481:United States / Q000453:epidemiology