This article describes a case of synchronous bilateral lung cancer, which was diagnosed with the use of molecular-ge-netics testing. Identification of two distinct KRAS mutations in tumors of right and left lungs supported independent origin of these neoplasms.

Diagnostics of genetic diseases in clinical routine often presents a challenge. In particular, most of hereditary diseases are exceptionally rare and therefore unfamiliar to practicing physicians. Furthermore, even if the diagnosis of a particular genetic condition appears convincing on the level of clinical evidence, the causative mutation often remains unknown due to limitations in DNA testing procedures. Recently developed high-throughput sequencing technologies (Next Generation Sequencing, NGS; synonym: massive parallel sequencing) provide a breakthrough in medical genetics. While in the past genetic testing was limited to a single gene or, at best, to a small number of genes, NGS is compatible with a large-scale DNA analysis. One of the most popular applications of NGS is whole exome sequencing (WES), which allows simultaneous reading of coding sequences (exons) of all known genes. Although this technology exists only for a few years, its use has already led to discovery of the causes of more than 150 genetic syndromes. Furthermore, WES may be recommended for the use in clinical routine for selected patients with orphan disease, especially for the families with multiple affected relative. It is likely that WES will become a powerful screening tool in the near future. This review discusses general principles of WES as well as the applications of this technology in medicine.

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«Liquid biopsy» is gradually becoming a mandatory procedure in cancer diagnostics. The aim of this procedure is to detect and monitor tumor-specific markers in various body fluids (blood, urine, pleural fluid, etc.). Significant efforts have been made to convert the most common mutational tests (EGFR, KRAS, BRAF) into non-invasive procedures. Despite some advantages, “liquid biopsy” is still not equivalent to traditional tissue analysis due to limited sensitivity and specificity; it cannot be routinely used in cancer medicine until the standardization of pre-analytical procedures is agreed. We intend to improve the performance of liquid biopsy for detection of a number of clinically relevant mutations (EGFR: ex19del and L858R; KRAS: 12, 13, 61, 146 codon nucleotide substitutions; BRAF: V600E). 417 plasma samples obtained from 88 patients (KRAS/NRAS/BRAF-mutated colorectal cancer (CRC): n= 57; EGFR-mutated lung adenocarcinomas (LC): n = 14; BRAF-mutated melanoma: n = 17) were analyzed by ddPCR for the presence of corresponding mutations in the circulating tumor DNA (ctDNA). Presence of tumor-specific mutations in plasma was confirmed in 32/57 (56%) CRC, 7/14 (50%) LC, and 4/17 (24%) melanoma cases. The proportion of mutation-positive plasma cases was tended to be higher in the group of patients with distant metastases compared to subjects with localized disease [34/56 (61%) vs. 5/15 (33%), р = 0.058]. 86 patients provided their blood at 9.00 (morning) and at 16.00 (afternoon). In addition, blood-takes were performed before and 15 minutes after usual breakfast as well as before and 15 minutes after moderate physical exercise. The detection rate of cancer-specific mutations in plasma was not significantly correlated with described above circumstances of blood-take. Meanwhile, the noticeable intrapatient variability of circulating mutation success rate has been detected. Thus, depending on clinical circumstances, at least negative ctDNA tests could be advised to be repeated in some patients, in order to ensure the reliability of results.

A patient with lung cancer carrying ROS1 translocation was treated by crizotinib and then subjected to surgery. Morphological analysis revealed pathologic complete response in surgically removed tissues, while PCR test provided convincing evidence for the presence of residual tumor cells. PCR analysis of lung cancer specific gene translocations allows carrying out highly sensitive and reliable monitoring of tumor disease during the course of treatment.