Background:Dihydropyrimidine dehydrogenase (DPD) catabolises ∼85% of the administered dose of fluoropyrimidines. Functional DPYD gene variants cause reduced/abrogated DPD activity. DPYD variants analysis may help for defining individual patients’ risk of fluoropyrimidine-related severe toxicity.Methods:The TOSCA Italian randomised trial enrolled colon cancer patients for 3 or 6 months of either FOLFOX-4 or XELOX adjuvant chemotherapy. In an ancillary pharmacogenetic study, 10 DPYD variants (*2A rs3918290 G>A, *13 rs55886062 T>G, rs67376798 A>T, *4 rs1801158 G>A, *5 rs1801159 A>G, *6 rs1801160 G>A, *9A rs1801265 T>C, rs2297595 A>G, rs17376848 T>C, and rs75017182 C>G), were retrospectively tested for associations with ⩾grade 3 fluoropyrimidine-related adverse events (FAEs). An association analysis and a time-to-toxicity (TTT) analysis were planned. To adjust for multiple testing, the Benjamini and Hochberg’s False Discovery Rate (FDR) procedure was used.Results:FAEs occurred in 194 out of 508 assessable patients (38.2%). In the association analysis, FAEs occurred more frequently in *6 rs1801160 A allele carriers (FDR=0.0083). At multivariate TTT analysis, significant associations were found for *6 rs1801160 A allele carriers (FDR<0.0001), *2A rs3918290 A allele carriers (FDR<0.0001), and rs2297595 GG genotype carriers (FDR=0.0014). Neutropenia was the most common FAEs (28.5%). *6 rs1801160 (FDR<0.0001), and *2A rs3918290 (FDR=0.0004) variant alleles were significantly associated with time to neutropenia.Conclusions:This study adds evidence on the role of DPYD pharmacogenetics for safety of patients undergoing fluoropyrimidine-based chemotherapy.

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BackgroundActivation of oncogenes downstream the EGFR gene contributes to colorectal tumorigenesis and determines the sensitivity to anti-EGFR treatments. The aim of this study was to evaluate the prognostic value of KRAS, BRAF, NRAS and PIK3CA mutations in a large collection of CRC patients from genetically-homogeneous Sardinian population.MethodsA total of 1284 Sardinian patients with histologically-proven diagnosis of colorectal carcinoma (CRC) and presenting with metastatic disease were included into the study. Genomic DNA was isolated from formalin-fixed, paraffin-embedded primary tumour tissue samples of CRC patients and screened for mutations in RAS and BRAF genes, using pyrosequencing assays, and in PIK3CA gene, using automated DNA sequencing assays.ResultsOverall, mutation rates were 35.6 % for KRAS, 4.1 % for NRAS, and 2.1 % for BRAF. Among available DNA samples, 114/796 (14.3 %) primary CRCs were found to carry a mutation in the PIK3CA gene. In this subset of patients analysed in all four genes, a pathogenetic mutation of at least one gene was discovered in about half (378/796; 47.5 %) of CRC cases. A mutated BRAF gene was found to steadily act as a negative prognostic factor for either time to progression as metastatic disease (from detection of primary CRC to diagnosis of first distant metastasis; p = 0.009) or partial survival (from diagnosis of advanced disease to the time of death or last control; p = 0.006) or overall survival (p < 0.001). No significant impact on prognosis was observed for mutated KRAS, NRAS, and PIK3CA genes or combined RAS mutations (all RAS).ConclusionsOur study defines both prevalence and prognostic role of main activated oncogenes in a population-based large collection of CRC patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-1053-z) contains supplementary material, which is available to authorized users.

BackgroundRole of KRAS, BRAF and PIK3CA mutations in pathogenesis of colorectal cancer (CRC) has been recently investigated worldwide. In this population-based study, we evaluated the incidence rates and distribution of such somatic mutations in genetically isolated population from Sardinia.MethodsFrom April 2009 to July 2011, formalin-fixed paraffin-embedded tissues (N = 478) were prospectively collected from Sardinian CRC patients at clinics across the entire island. Genomic DNA was isolated from tissue sections and screened for mutations in KRAS, BRAF, and PIK3CA genes by automated DNA sequencing.ResultsOverall, KRAS tumour mutation rate was 30% (145/478 positive cases). Distribution of mutation carriers was surprisingly different within the island: 87/204 (43%) in North Sardinia vs. 58/274 (21%) in Middle-South Sardinia (p<0.001). Among 384 CRC cases whose DNA was available, only one (0.3%) patient carried a mutation in BRAF gene; PIK3CA was found mutated in 67 (17%) patients. A significant inverse distribution of PIK3CA mutation rates was observed within Sardinian population: 19/183 (10%) cases from northern vs. 48/201 (24%) cases from central-southern island (p<0.001). This heterogeneity in frequencies of KRAS/PIK3CA somatic mutations is consistent with already-reported discrepancies in distribution of germline mutations for other malignancies within Sardinian population. Preliminary clinical evaluation of 118 KRAS wild-type patients undergoing anti-EGFR-based treatment indicated lack of role for PIK3CA in predicting response to therapy.ConclusionsOur findings support the hypothesis that differences in patients’ origins and related genetic backgrounds may contribute to even determine the incidence rate of somatic mutations in candidate cancer genes.

We investigated 17 polymorphisms in 11 genes (TS, MTHFR, ERCC1, XRCC1, XRCC3, XPD, GSTT1, GSTP1, GSTM1, ABCC1, ABCC2) for their association with the toxicity of fluoropyrimidines and oxaliplatin in colorectal cancer patients enrolled in a prospective randomized trial of adjuvant chemotherapy. The TOSCA Italian adjuvant trial was conducted in high-risk stage II–III colorectal cancer patients treated with 6 or 3 months of either FOLFOX-4 or XELOX adjuvant chemotherapy. In the concomitant ancillary pharmacogenetic study, the primary endpoint was the association of polymorphisms with grade 3–4 CTCAE toxicity events (grade 2–4 for neurotoxicity). In 517 analyzed patients, grade ≥ 3 neutropenia and grade ≥ 2 neurotoxicity events occurred in 150 (29%) and in 132 patients (24.8%), respectively. Diarrhea grade ≥ 3 events occurred in 34 (6.5%) patients. None of the studied polymorphisms showed clinically relevant association with toxicity. Hopefully, genome-wide association studies will identify new and more promising genetic variants to be tested in future studies.