| Objective: With the development of medical diagnosis and treatment technology and the prolongation of survival of patients with cancer,multiple primary cancers are found in more and more patients with cancer in the same or other organs during follow-up.Studies have shown that most second primary cancers may occur unclearly and involve different mechanisms,including treatment,environmental factors and the effects of genetic predisposition on second primary cancer.And colorectal cancer is the most common in second primary cancers.The location and histology of the second primary colorectal cancer(SPCRC)is different from those of initial primary cancer,but do not include the metastasis and recurrence of the initial primary colorectal cancer(IPCRC)in a patient.SPCRC may also occur at the same site,but anatomically different from IPCRC,so it is not the metastasis or recurrence of IPCRC.Studies have confirmed that there is no significant difference in prognosis between IPCRC and SPCRC patients undergoing surgical treatment.However,this analysis is not based on nationwide data,nor further stratified by age of diagnosis,p TNM stage and other prognostic factors.To date,little research has been done to study and evaluate the prognosis and survival of IPCRC and SPCRC.Therefore,based on nationwide data,the comparison between IPCRC and SPCRC in p TNM stage,primary location,age of diagnosis,therapeutic effect and survival of prognosis is unclear.Hence,the aim of the study was to compare the prognosis and therapeutic effect between IPCRC and SPCRC.Methods: The National Cancer Institute's Surveillance,Epidemiology,and End Results(Surveillance,Epidemiology,and End Results,SEER)database was used to assess in the study.This study included 377271 cases of IPCRC and 18617 cases of SPCRC,which were diagnosed from 1988 to 2015.The study endpoint were cancer specific survival(CSS)and overall survival(OS).SEER STAT and Stata MP 14(Stata Corp LP,College Station,TX,USA)were used to extract the data of the patients,and IBM SPSS 20(IBM Corporation,Armonk,NY,from SEER data.USA)was used for statistical analysis.P<0.05 was considered to be statistically significant in all statistical analysis.?2 test was used to analyse categorical variables whether there was a significant relationship between IPCRC and SPCRC.CSS and OS were measured by Kaplan-Meier survival curve and compared by log-rank test.COX regression was to analyse multivariate and univariate analysis,and COX proportional hazard model was established.The therapeutic effect of IPCRC and SPCRC was evaluated with adjusted hazard ratio(HR)and 95% confidence interval(95%CI).Interaction analysis was added to the COX proportional hazard model to establish the correlation,and the statistical significance of the Cox proportional hazard model is determined by the likelihood ratio.Results: The cancer-specific survival rate of patients with IPCRC was significantly higher than that of patients with SPCRC(5-years survival rate:64.85% vs.60.22%,P<0.001).Meanwhile,when analyzed by OS,patients with SPCRC hold worse OS than those with IPCRC(HR=1.102;95% CI=1.081-1.123;P<0.001).The Chi-square of stratified log rank for age at diagnosis was lower than that for primary site,p TNM stage,sex,race,histology,and grade(CSS,Chi-square=86.73;OS,Chi-square=131.4).There were almost no differences on therapeutic benefits between patients with IPCRC and SPCRC,except that treatments with chemotherapy were significantly associated with longer CSS and OS compared with treatments without chemotherapy among stage III surgical IPCRC and SPCRC left-sided colon cancers patients(CSS,HR=0.764 vs.0.581,P-interaction=0.008;OS,HR=0.703 vs.0.545,P-interaction=0.026).Conclusion: Patients with SPCRC have worse prognosis than those with IPCRC primarily because of older age in the former group.The results evidenced that the therapeutic benefits on the prognosis for colorectal cancer were generally similar between patients with IPCRC and SPCRC. |
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