Second primary cancer after surgery for colorectal cancer without lymph node metastasis

Background/Aims: Colorectal cancer patients without lymph node metastasis usually show a favorable prognosis with low recurrence rates; however, there is an increased risk of the development of a second primary cancer. Understanding the features of a second primary cancer is important to establish an effective postoperative follow-up program for colorectal cancer without lymph node metastasis. Methodology: The clinicopathological data on 801 patients with Dukes' A and Dukes' B colorectal cancer were examined in respect to second primary cancer. Results: In patients with Dukes' A cancer, the incidences of recurrence and second primary cancer were similar. When tumor invasion was limited within subserosa in Dukes' B patients, the incidence of a second primary cancer was almost two-thirds that of recurrence. More than half of the second primary cancers again developed from the colorectum, followed by stomach and lung. Conclusions: When colorectal cancer patients without lymph node metastasis show tumor invasion limited within the subserosa, postoperative follow-up should monitor a balance of recurrence with a second primary cancer.