Multiple primary malignancies involving colorectal cancer-clinical characteristics and prognosis with reference to surveillance

The purpose of this study was to investigate clinically useful information for effective screening for synchronous and metachronous second primary cancers and to suggest potential surveillance tool. We retrospectively reviewed 1,063 patients who were treated with potentially curative surgery for colorectal cancer at Gachon University, Gil Hospital from 1997 to 2007. The incidence of synchronous or metachronous cancer in addition to colorectal cancer was 5.3% (57 patients). The most common second primary cancer was stomach (54.3%), followed by cancers in cervix (12.2%). The time interval between the first and second tumor in colorectal cancer associated with metachronous extracolonic malignancy ranged from 1.1 to 10.8 years. The incidence of early-stage tumor was higher in patients with synchronous cancer than in those with a metachronous cancer with statistical significance (p = 0.034). The 5-year survival rate of the colorectal cancer group without second primary cancer was 70.1%, whereas that for the second primary cancer group was 63.8% (p = 0.253). The 5-year survival rate of the colorectal cancer group with stomach cancer was 70.5%, whereas that for the second primary cancer other than stomach cancer group was 56.6% (p = 0.282). The frequent association between colorectal cancer and gastric cancer suggests an inclusion of gastrofiberscope when surveillancing patients with colorectal cancer in Korean population. Second primary cancers may develop even 10 years after the initial operation; thus, a need for lifelong surveillance even more than 5 years may be necessary.