Can we improve the cytologic examination of malignant pleural effusions using molecular analysis?
BACKGROUND
Currently, 40% of patients remain undiagnosed after routine cytologic examination for malignant pleural effusions. Deoxyribonucleic acid (DNA) methylation is a robust strategy for detecting cancer early in tissue. We hypothesized that DNA methylation would be more sensitive in diagnosing patients with malignant pleural effusions than cytology.


METHODS
We conducted a prospective cohort study of 31 inpatients with pleural effusions (24 malignant pleural effusions metastatic from 10 different organs and 7 benign) over 18 months. Aspirated pleural fluid underwent cytologic examination and DNA extraction for nested methylation-specific polymerase chain reaction (PCR). We assayed for promoter hypermethylation in 8 genes known to be methylated in many cancers. Pleural fluid was considered positive if 2 or more genes were methylated by methylation-specific PCR.


RESULTS
Cytology alone confirmed malignant pleural effusions in 15 of 24 patients (sensitivity 63%), whereas methylation alone positively identified 16 of 24 patients (sensitivity 67%). Both tests had 100% specificity in predicting benign effusions. If cytology and methylation were considered together, they exhibited 88% sensitivity and 100% specificity in discriminating benign and malignant effusions. Combined, the two assays were more sensitive than either test alone. Although the positive predictive value of each test was 100%, the negative predictive value of cytology and methylation combined was 78%, better than 47% and 44% for methylation and cytology alone, respectively.


CONCLUSIONS
Epigenetic analysis of pleural fluid can detect malignant DNA from a variety of neoplasms, provide complementarity with cytology, and improve the diagnostic yield of the current standard examination of pleural fluid.
Brock
Malcolm V
MV
Division of Thoracic Surgery, Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA. mabrock@jhmi.edu
Hooker
Craig M
CM
Yung
Rex
R
Guo
Mingzhou
M
Han
Yu
Y
Ames
Stephen E
SE
Chang
David
D
Yang
Stephen C
SC
Mason
David
D
Sussman
Marc
M
Baylin
Stephen B
SB
Herman
James G
JG
D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000473:pathology; D015331:Cohort Studies; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000473:pathology; D008297:Male; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D016066:Pleural Effusion, Malignant / Q000235:genetics* / Q000473:pathology*; D011446:Prospective Studies; D012680:Sensitivity and Specificity