Abstract
The selection of proper tissues from formalin-fixed and paraffin-embedded tumors before diagnostic molecular testing is responsibility of the pathologist and represents a crucial step to produce reliable test results. The international guidelines suggest two cut-offs, one for the percentage and one for the number of tumor cells, in order to enrich the tumor content before DNA extraction. The aim of the present work was two-fold: to evaluate to what extent a low percentage or absolute number of tumor cells can be qualified for somatic mutation testing; and to determine how assay sensitivities can guide pathologists towards a better definition of morphology-based adequacy cut-offs. We tested 1797 tumor specimens from melanomas, colorectal and lung adenocarcinomas. Respectively, their BRAF, K-RAS and EGFR genes were analyzed at specific exons by mutation-enriched PCR, pyrosequencing, direct sequencing and real-time PCR methods. We demonstrate that poorly cellular specimens do not modify the frequency distribution of either mutated or wild-type DNA samples nor that of specific mutations. This observation suggests that currently recommended cut-offs for adequacy of specimens to be processed for molecular assays seem to be too much stringent in a laboratory context that performs highly sensitive routine analytical methods. In conclusion, new cut-offs are needed based on test sensitivities and documented tumor heterogeneity.
Highlights
The identification of biologically active genes and pathways that are disrupted in various cancer types has led to the development of clinically relevant diagnostic requirements
All samples were submitted to DNA sequence analyses irrespective of their A or not acceptable (NA) status
We compared the frequency of NA in the metastatic colorectal cancers (mCRCs) and non-small cell lung cancers (NSCLCs) specimens that were analyzed with different morphological criteria of unsuitability
Summary
The identification of biologically active genes and pathways that are disrupted in various cancer types has led to the development of clinically relevant diagnostic requirements. Anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibodies (Cetuximab and Panitumumab) were approved for the treatment of wild-type RAS metastatic colorectal cancers (mCRCs) and anti-tyrosine kinases (Erlotinib and Vemurafenib) were admitted in therapeutic schemes to treat EGFR mutated non-small cell lung cancers (NSCLCs) and BRAFmutated metastatic melanomas (mMELs), respectively. The conditions of their clinical uses were determined by specific trials (CRYSTAL, IPASS, BRIM-1, PEAK and PRIME), designed on the basis of results from retrospective studies [5,6,7,8]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have