Molecular testing of different cytologic preparations in patients with advanced lung adenocarcinoma: which yields the best results?

Concordance of Cytological Specimens with Histological Tissue for Detection of Epidermal Growth Factor Receptor Mutation in Non-Small Cell Lung Cancer: A Systematic Review

INTRODUCTION

There is increasing need for more testing in non-small cell lung cancer given the introduction of newer targeted therapies. Cytological specimens including conventional smears (CS), cell blocks (CB), and liquid-based cytology (LBC) are an alternative to histologic tissue (HT) specimens in detecting EGFR mutations, but the concordance of these 2 specimens is yet to be determined. The aim of the present systematic review is to determine the concordance rates between different cytologic specimens with HT in detecting EGFR mutations.

METHODS

PubMed, Cochrane Library, and Google Scholar were utilized in the primary search, along with reference lists of electronically retrieved full-text articles. Concordance rates were pooled together if 2 or more studies reporting the same type of cytologic specimen were available.

RESULTS

Overall, 15 studies were included in this review, with 13 studies included in the pooled analysis. There was an overall concordance rate of 92.8% in 593 paired cytologic and HT specimens, with LBC having the highest concordance rate of 96.0%, followed by CS and CB, each with a concordance rate of 95.8%, although the concordance rate of CS and/or CB was lower at 90.6% with a larger pool of studies. LBC was found to have a significantly higher concordance rate than CS and/or CB.

CONCLUSION

Cytological specimens have a high concordance rate in detecting EGFR mutations, when compared to HT. LBC has shown superior concordance rates compared to CS and CB. Cytological specimens should be considered as an additional and alternative source of diagnostic material for EGFR testing.

ALK and ROS1 rearrangement tested by ARMS-PCR in non-small-cell lung cancer patients via cytology specimens: The experience of Shanghai Pulmonary Hospital

BACKGROUND

Cytology specimens are the main samples used for the diagnosis of advanced lung cancer. The objective of our study was to assess anaplastic lymphoma kinase (ALK) and c-ros oncogene 1 receptor tyrosine kinase (ROS1) genes by an amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) using cytology specimens and to then evaluate the mutation frequency of ALK and ROS1 in non-small-cell lung cancer (NSCLC) patients.

METHODS

A large cohort that consisted of 8180 NSCLC patients who were genetically tested using cytology samples or formalin-fixed and paraffin-embedded (FFPE) samples (tumor tissue or biopsy) from January 2015 to December 2018 were screened. The gene rearrangement ratio and clinical characteristics of the two sample groups were analyzed by SPSS software.

RESULTS

In our hospital, cytology specimens are the main resource used for gene testing in NSCLC. In most cases, an abundant quantity of nucleic acid was extracted from the residual liquid-based cell pellet for testing the ALK and ROS1 genes. In certain cases, when the residual cell pellet was insufficient for the gene testing, the cell block and liquid-based cell smear served as alternative options. In addition, we retrospectively analyzed our previous data, and the mutation ratio of the ALK/ROS1 rearrangements obtained by using the cytology samples (4.98%/1.80%) and the FFPE samples (6.06%/1.62%) was almost the same (P-value = .09/.634).

CONCLUSIONS

This study demonstrated that AMRS-PCR method can effectively identify ALK and ROS1 gene rearrangements and cytology specimens might be an excellent source for routine molecular testing in patients with advanced NSCLC.

Cytology smears for DNA extraction: Practical approach for selecting the best slide

BACKGROUND

Next generation sequencing (NGS) to detect actionable genetic abnormalities is standard of care in advanced stage lung adenocarcinoma. Many studies have shown that the molecular results obtained from fine needle aspiration cytology material are comparable to those obtained from formalin-fixed tissue samples. We undertook this study to validate DNA extraction from cytology material for molecular studies and to find any correlation between DNA yield, pattern of tumour cells and tumour fraction.

METHODS

DNA was extracted from 34 cytology slides of pulmonary adenocarcinoma cases with predetermined EGFR mutation status. Cytology slides were reviewed for pattern of tumour distribution and tumour fraction. NGS was performed on five slides with variable DNA and compared with original results.

RESULTS

There were 14 alcohol-fixed and 20 air-dried smears. The mean DNA yield was 1.74 μg and median of 0.4 μg (range, 0.02-21 μg). Tumour fractions varied from 10% to 90%. No correlation was found between tumour fraction and DNA yield (P = 0.14). The mean DNA yield was high in slides with tumour throughout the slide (sheets or scattered clusters) as compared to rare scattered clusters and/or single cells. EGFR mutation was found in four of the five cases sent for NGS lung panel while one case revealed BRAF mutation.

CONCLUSIONS

DNA with good quantity and quality can be extracted from the cytology slides for NGS irrespective of type of fixation. DNA yield has better correlation with distribution pattern of tumour cells on the slides rather than tumour fraction.