Features of synchronous and metachronous dual primary gastric and colorectal cancer

BACKGROUND Studies evaluating the characteristics of dual primary gastric and colorectal cancer(CRC)(DPGCC)are limited.AIM To analyze the clinicopathologic characteristics and prognosis of synchronous and metachronous cancers in patients with DPGCC.METHODS From October 2010 to August 2021,patients with DPGCC were retrospectively reviewed.The patients with DPGCC were divided into two groups(synchronous and metachronous).We compared the overall survival(OS)between the groups using Kaplan-Meier survival methods.Univariate and multivariate analyses were performed using Cox’s proportional hazards model to identify the independent prognostic factors for OS.RESULTS Of the 76 patients with DPGCC,46 and 30 had synchronous and metachronous cancers,respectively.The proportion of unresectable CRC in patients with synchronous cancers was higher than that in patients with metachronous cancers(28.3%vs 3.3%,P=0.015).The majority of the second primary cancers had occurred within 5 years.Kaplan-Meier survival analysis showed that the patients with metachronous cancers had a better prognosis than patients with synchronous cancers(P=0.010).The patients who had undergone gastrectomy(P<0.001)or CRC resection(P<0.001)had a better prognosis than those who had not.In the multivariate analysis,synchronous cancer[hazard ratio(HR)=6.8,95%confidence interval(95%CI):2.0-22.7,(P=0.002)]and stage III-IV gastric cancer(GC)[HR=10.0,95%CI:3.4-29.5,(P<0.001)]were risk prognostic factor for OS,while patients who underwent gastrectomy was a protective prognostic factor for OS[HR=0.2,95%CI:0.1-0.6,P=0.002].CONCLUSION Regular surveillance for metachronous cancer is necessary during postoperative follow-up.Surgical resection is the mainstay of therapy to improve the prognosis of DPGCC.The prognosis appears to be influenced by the stage of GC rather than the stage of CRC.Patients with synchronous cancer have a worse prognosis,and its treatment strategy is worth further exploration.