Colorectal cancer in cases of multiple primary cancers: Clinical features of 59 cases and point mutation analyses

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.