Lung cancer screening in the randomized Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial.
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.
Hocking
William G
WG
Department of Clinical Oncology, Marshfield Clinic, 1000 North Oak Avenue, Marshfield, WI 54449, USA. hocking.william@marshfieldclinic.org
Hu
Ping
P
Oken
Martin M
MM
Winslow
Stephen D
SD
Kvale
Paul A
PA
Prorok
Philip C
PC
Ragard
Lawrence R
LR
Commins
John
J
Lynch
David A
DA
Andriole
Gerald L
GL
Buys
Saundra S
SS
Fouad
Mona N
MN
Fuhrman
Carl R
CR
Isaacs
Claudine
C
Yokochi
Lance A
LA
Riley
Thomas L
TL
Pinsky
Paul F
PF
Gohagan
John K
JK
Berg
Christine D
CD
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