Mismatch Repair Deficiency in Patients with Double Primary Cancer of the Colorectum and Stomach

We examined the correlation between the expression of mismatch repair (MMR) gene proteins and the development of double primary cancer, and studied clinical implications of an MMR deficiency in 15 patients with double primary cancer of the colorectum and stomach, immunohistochemically. The results were compared between the double primary cancer group of 15 patients and the control group consisting of 155 colorectal cancer (CRC) patients who had never developed other malignant diseases. Patients with hereditary nonpolyposis colorectal cancer and familial adenomatous polyiposis were excluded from both groups. The MMR deficiency in CRC was significantly more frequently detected in the double primary cancer group than in the control group (46.7% versus 20.6%, P < 0.05). Patients with MMR-deficient CRC of the double primary cancer group were significantly older, more frequently had poorly differentiated lesions, had less metastases to the liver and lymph node, and were more advanced in depth of invasion than those of the control group. We concluded that MMR deficiency might correlate with the development of double primary cancer of the colorectum and stomach. Patients with MMR-deficient CRC need periodical and intensive follow-up against the development of double primary cancer.