右側大腸癌における予後と補助化学療法の適応

Impact of Right-sided Tumor Location on Survival in Stage II～III Colorectal Cancer : Implication for Adjuvant Chemotherapy

要旨　目的：Stage II～III大腸癌における右側と左側の臨床像や予後の差異を明らかにし，右側，左側における補助化学療法の適応を検証する．対象：1991～2005年に当院で根治切除されたStage II～III大腸腺癌1,568例（Stage II/III 747/821例）を対象とした．結果：右側大腸癌は左側大腸癌に比べ高齢で女性が多く，T4が多く，リンパ節転移が少なく，腫瘍径が大きく，低分化腺癌・粘液癌・印環細胞癌が多かった．Stage IIでは右側大腸癌の予後は左側大腸癌に比べ良好であったが，Stage IIIでは差を認めなかった．ASCO，ESMOに規定されたhigh risk Stage IIは左側大腸癌では予後不良だったが，右側大腸癌では差を認めなかった．結論：Stage II右側大腸癌の補助化学療法の適応決定には，新たな再発危険因子の同定が必要である．

　Aim : To elucidate the difference in survival and clinicopathological characteristics between right-sided and left-sided Stage II～III colorectal adenocarcinoma in order to verify the indication for adjuvant chemotherapy in these tumors.

　Object : Consecutive patients with Stage II～III colorectal adenocarcinoma undergoing curative surgery in the Cancer Institute Hospital during the period of 1991～2005. A total of 1,568 patients were enrolled in the study, including 747 Stage II and 821 Stage III colorectal cancers.

　Results : Right-sided colon cancer showed higher age, female prevalence, more T4 tumors, less lymph node metastasis, larger tumor size and a higher proportion of poorly-differentiated/mucinous/signet-ring cell adenocarcinomas than left-sided colorectal cancer. Right-sided Stage II colon cancer had better survival than left-sided Stage II cancer, while there was no difference in survival between right-sided and left-sided Stage III cancers. High risk Stage II as defined in ASCO or ESMO guidelines showed poor survival in left-sided colorectal cancer, while there was no decline in survival in right-sided high risk Stage II cancer.

　Conclusions : A new definition of high risk Stage II is needed for right-sided Stage II colon cancer in order to determine the indication for adjuvant chemotherapy.