Molecular Profiling of Malignant Pleural Effusion in Metastatic Non-Small-Cell Lung Carcinoma. The Effect of Preanalytical Factors.

RATIONALE

Non-small-cell lung cancer (NSCLC)-associated malignant pleural effusions (MPEs) are sometimes the only available specimens for molecular analysis.

OBJECTIVES

This study evaluates diagnostic yield of NSCLC-associated MPE, its adequacy for molecular profiling and the potential influence of MPE volume/cellularity on the analytic sensitivity of our assays.

METHODS

Molecular results of 50 NSCLC-associated MPE cases during a 5-year period were evaluated. Molecular profiling was performed on cell blocks and consisted of fluorescent in situ hybridization (FISH) for ALK gene rearrangements and the following sequencing platforms: Sanger sequencing (for EGFR) and high-throughput pyrosequencing (for KRAS and BRAF) during the first 4 years of the study period, and targeted next-generation sequencing performed thereafter.

RESULTS

A total of 50 NSCLC-associated MPE cases were identified where molecular testing was requested. Of these, 17 cases were excluded: 14 cases (28%) due to inadequate tumor cellularity and 3 cases due to unavailability of the slides to review. A total of 27 out of 50 MPE cases (54%) underwent at least EGFR and KRAS sequencing and FISH for ALK rearrangement. Of the 27 cases with molecular testing results available, a genetic abnormality was detected in 16 cases (59%). The most common genetic aberrations identified involved EGFR ( 9 ) and KRAS ( 7 ). Six cases had ALK FISH only, of which one showed rearrangement. MPE volume was not associated with overall cellularity or tumor cellularity (P = 0.360).

CONCLUSIONS

Molecular profiling of MPE is a viable alternative to testing solid tissue in NSCLC. This study shows successful detection of genetic aberrations in 59% of samples with minimal risk of false negative.