Multiple primary cancers in extracolonic sites with colorectal cancer

The present study was undertaken to clarify the clinical and pathological features of multiple primary cancers, especially those at extracolonic sites, in patients with colorectal cancers. We reviewed the records of 2,176 patients who underwent surgery for colorectal cancers in our institute from January 1997 to December 2006. A synchronous multiple primary cancer was defined as extracolonic cancer detected within 6-month interval before and after the detection of colorectal cancer. Any metastasis from colorectal cancers was excluded. Synchronous multiple primary cancers were identified in 32 patients. The stomach is the most common organ for synchronous multiple primary cancer development in patients with colorectal cancers (0.9%, 20/2,176). Gastric cancer is the most common synchronous multiple primary cancers occurring concomitantly with colorectal cancers. Careful preoperative screening is necessary for the detection of multiple primary cancers in extracolonic sites in patients with colorectal cancers.