The present study aimed to investigate the occurrence and clinical features of cases of multiple primary cancers including colorectal cancer (MPCC). The medical records of patients with colorectal cancer (CRC) who underwent surgery at the Third Xiangya Hospital of Central South University (Changsha, China) between August 2007 and August 2014 were retrospectively analyzed. Patients with MPCCs were identified and mutation analyses were performed on colon specimens. The results revealed that among 1,311 patients with CRC, 59 had MPCC (including 35 cases of ≥1 CRC with ≥1 other cancer type, and 24 cases with multiple CRCs and no other primary cancers). Foci occurred on the right side of the colon (n=32), in the rectum (n=28), and on the left side of the colon (n=24). MPCCs were synchronous in 24 patients, metachronous in 32 patients, and both in 3 patients. Age of onset and presence of polyps were identified as significantly different between MPCC and CRC overall (P<0.05); however, sex or adenoma incidence were not observed to differ significantly between groups. Mutation incidence rates in 26 specimens were 11.54% for KRAS proto-oncogene GTPase (KRAS) G13D, 3.85% for KRAS Q61R and 3.85% B-Raf proto-oncogene serine/threonine kinase V600E. Mutations of exon 21 of the epithelial growth factor receptor gene, including L858R and L861Q, and of KRAS G12V were not detected. In conclusion, the likelihood of occurrence of MPCC is closely associated with the age of onset and the presence of polyp(s). Routine examination of multiple systems is necessary for patients with CRC to avoid missed diagnosis and misdiagnosis. Further study is required to demonstrate the molecular mechanism of CRC in cases of multiple primary cancers.

Background/aim: This study aimed to investigate the relationship between single nucleotide polymorphisms (SNPs) of cancer-related genes and the risk of multiple primary malignancies involving colorectal cancer. Materials and methods:We collected tissue samples from 22 multiple primary cancer patients with primary colorectal cancer and performed genotyping assay for 116 SNP loci from 62 genes encoding peptides functioning in various signaling pathways using the DNA MassARRAY system. The chi-square test was used to compare the differences in base frequencies between patients and a control Chinese population from HapMap through the NCBI database.Results: No significant differences in frequencies were detected for 81 SNPs (P > 0.05), while serious frequency differences were observed for 35 SNPs from 31 genes (P < 0.05), which included ERCC6 (rs2228526), ERCC1 (rs3212986), CASP8 (rs3834129, rs3769818), and others presented. Five of these SNPs were previously reported to be associated with the pathogenesis of colorectal cancer. Conclusion:The 35 SNPs from 31 genes may be associated with the risk of multiple primary malignancies involving colorectal cancer.