多発大腸癌の実態と臨床診断―単発癌との比較

Clinical Characteristics of Multiple Colorectal Cancers

要旨　遺伝性非ポリポーシス大腸癌（HNPCC）を除く大腸多発癌の発生頻度は約4％であった．単発癌に比べ，同時性多発癌は男性に多い傾向が認められた．また多発癌症例にHNPCCの特徴である若年発症の傾向や右側結腸癌が多発する傾向が認められ，一部の多発癌に臨床診断基準を満たしていないHNPCC症例が混在することが示唆された．同時性多発癌は，単発癌に比べ予後不良傾向が認められた．異時性多発癌の初発癌から第2癌，あるいは第2癌から第3癌までの発生間隔を検討してみると，前回手術から2～3年目と8～9年目にピークを認め，2峰性の分布を示し，第1のピークに含まれる症例には前回手術時の見落とし例があることが示された．

　In order to clarify clinical characteristics of multiple colorectal cancers, we examined the clinicopathological backgrounds of patients with multiple colorectal cancers and compared them with those of patients with single cancer. 4,028 colorectal cancer patients with more than pT2 tumors were treated consecutively at the National Cancer Center Hospital from 1963 to 1998. Among them, 153 patients (4%) were found to have multiple colorectal cancers. Hereditary non-polyposis colorectal cancers (HNPCCs) were not included. There was a higher ratio of multiple cancers than single cancers in both male and female subjects. This was significant among synchronous multiple cancers (p=0.0002). Because the patients with multiple colorectal cancers had some of the characteristics of HNPCC such as a high incidence of right colon cancer, and a higher incidence among the young. Some HNPCC patients who do not fulfill HNPCC criteria might be included among the patients with multiple cancers. Prognosis of patients with synchronous multiple cancers was worse than that of patients with single cancer, but it was not significant. Incidence of multiple colorectal cancers was biphasic with a peak during the first 2～3 years and another after 8～9 years. There was some unnoticed synchronous cancers or adenomas in the first peak. Thus, careful examination to detect another lesion at the original cancer diagnosis was important for preventing metachronous cancers.