[Frequency and characteristics of secondary cancer in the colon and rectum after primary resection]

Among 2087 patients who underwent primary resection of colorectal cancer in our department within the past 20 years, 68 (3.2%) were found to have a secondary or additional cancer in their large bowel after the first resection. Statistically significant risk factors in the secondary cancer group were a high incidence of coexisting adenoma and high frequency of colorectal cancer in second-degree relatives. Those in whom secondary cancer occurred were divided into two groups: the adenoma component (AC) group; and the non-adenoma component (DN) group. Secondary cancer in the DN group revealed lower grade of cell differentiation and more frequent depressed macroscopic findings than in the AC group. As a result, the prognosis of the DN group was worse than that of the AC group (p < 0.05). Based on these results, the recommended follow-up should include colonoscopy in the first years after primary cancer resection and according to the findings of the first colonoscopy the frequency of colonofiberscopic follow-up must be decided.