Molecular profile in Paraguayan colorectal cancer patients, towards to a precision medicine strategy

Abstract

Somatic mutation analysis and evaluation of microsatellite instability (MSI) have become mandatory for selecting personalized therapy strategies for advanced colorectal cancer and are not available as routine methods in Paraguay. The aims of this study were to analyze the molecular profile as well as the microsatellite status in a series of advanced colorectal patients from two public hospitals from Paraguay, to introduce these methodologies in the routine practice to guide the therapeutic decisions. Thirty-six patients diagnosed with advanced colorectal cancer from two referent public hospitals from Paraguay were recruited from May 2017 to February 2018. Sequenom Mass spectrometry, Oncocarta Panel V.1 was applied to analyze the mutational profile from formalin-fixed paraffin-embedded samples. The microsatellite status was tested by immunohistochemistry (IHC). The mean age of the patients was 52 years with a range from 20 to 74 years. Eighty-three percent of the patients included in the study have advanced-stage tumors at the moment of the diagnosis. Sixteen patients (44.4%) were wild-type for all the oncogene regions analyzed with the Oncocarta panel. Thirty-two hot-spot pathogenic variants on seven oncogenes, among 20 patients (55.6%), were identified, including KRAS, NRAS, BRAF, PI3KCA, FGFR, epidermal growth factor receptor, and PDGFRA. Moreover, 14 (38.8%) of these patients presented pathogenic variants in KRAS/NRAS or BRAF genes that have implications in the clinical practice decisions. Five patients (14%) presented MSI. The IHC study for microsatellite status and the molecular profile analysis through Sequenom mass spectrometry are feasible and useful methods, due to identify those patient candidates for targeted therapies and for the budgetary calculations of the National Health Plans.

Keywords: Oncocarta; colorectal cancer; microsatellite instability; mutational profile; precision medicine.

Figure 1

Demographic characteristics of the series. A, Percentage of patients recruited from the two different participating centers: INCAN, Instituto Nacional del Cáncer; HC, Hospital de Clínicas, (B) percentage of patients with right (green) and left (blue) location of tumor lesions, (C) distribution of men and women among the samples analyzed, (D) distribution of patients according to the age at the moment of diagnosis > or <50 years old

Figure 2

Mutational Waterfall plot of the patients’ dataset. Data have been obtained by analyzing the Oncocarta^™ v1.0 panel (MassARRAY^R System by Agena Bioscience^™). Visualization of the plot by cBioportal‐OncoPrimer v1.18.032, 33 (www.cbioportal.org/OncoPrimer). Colored squares mean the type of alteration detected: green indicates missense mutation, whereas black identifies truncating mutation. All grey squares identify one patient; when they are without any other color means that no alterations are present in the sample

Figure 3

Mapping of Mutations detected in seven oncogenes. Lolliplots have been draw with cBioportal‐Mutation Mapper v1.18.0 (www.cbioportal.org/MutationMapper).32, 33 The plot identifies the different domains in each respective protein. The nature of the mutations and its position is shown. The number of times each mutation has been detected is shown with the left scale and is represented by the height of dot. A, KRAS, (B) PIK3CA, (C) NRAS, (D) BRAF, (E) EFGR, (F) PDGFRA, and (G) FGFR1

Figure 4

Immunohistochemistry study of mismatch repair proteins expression. Complete loss of nuclear staining for MSH6 and MSH2 in tumor cells, with positive internal control in stromal lymphocytes and fibroblasts (A: MSH6 40×, D: MSH2 40×) Retained MLH1 and PMS2 nuclear expression in tumor cells (B: MLH1 40×, C: PMS2 40×)

Figure 5

Kaplan‐Meier curves of tumor‐specific survival (TSS) of the colorectal cancer patients. A, Tumor‐specific survival of the all series. B, Tumor‐specific survival according to the tumor location (left vs right). C, Tumor‐specific survival according to the gender (males vs females). D, Tumor‐specific survival according to the treatment administered (chemotherapy + antiangiogenics vs chemotherapy alone). E, Tumor‐specific survival according to the mutation profile (mutated/no mutated). F, Tumor‐specific survival according to the mutation profile: KRAS vs other mutations