内視鏡的経過例からみた早期胃癌の深達度と時間的推移―特にM癌からSM癌への発育進展速度に関与する遅速因子について

Depth of Invasion and Time Course of Early Gastric Cancer Based on Cases Followed up Endoscopically : With Special Reference to Slow Factors Involved in the Speed of Growth and Progression from M Cancers to SM Cancers

要旨　内視鏡的に6か月以上経過観察しえた早期胃癌105病変を対象とし，壁深達度が進展する速度について検討した．（1）M癌，SM癌の進展頻度と進展速度：M癌の平均観察期間は46か月で進展頻度は30.0％（M癌からSM癌16.7％，M癌から進行癌13.3％）でSM癌の平均観察期間は23か月であり，SM癌から進行癌73.3％でSM癌の進展頻度が有意に高かった（p＝0.001）．M癌の進展期間にはSM癌と比較して大きな幅があり，早期癌における発育進展の多様性はM癌の時期に規定されると推定した．（2）早期癌の累積進展率：累積進展率50％に要する推定時間はM癌からSM癌で85か月，SM癌から進行癌で31か月で，SM癌から進行癌への進展はM癌からSM癌への進展と比較して進展速度が有意に速かった（p＜0.0001）．（3）M癌からSM癌への進展に影響する因子：年齢，肉眼型などの臨床病理学的因子別に累積進展率を比較したが，すべての因子において有意差は認めなかった．そこで，M癌のうち4年未満に進展した急速発育群（RG群）11病変と4年以上進展しなかった遅発育群（SG群）15病変を抽出し臨床病理学的因子別に頻度を比較した結果，組織型で高・中分化型腺癌主体群と低分化型腺癌・印環細胞癌主体群に頻度差はなく，超高分化型腺癌主体群は他2群と比較してSG群の頻度が有意に高かった（p＝0.02, 0.006）．以上の成績より，内視鏡的にM癌からSM癌まで要する平均的な時間は7年程度，SM癌から進行癌まで2～3年程度と推測した．各種の臨床所見よりM癌の発育進展の予測因子は特定できなかったが，sub解析では病理組織学的に超高分化型腺癌，あるいはそれを主体としたM癌においては極めて遅い発育進展がありうると推測される．

　We investigated the speed at which depth of invasion of the gastric wall progressed in 105 early gastric cancer lesions whose course it was possible to follow up endoscopically for 6 months or more. （1）Frequency of progression and speed of progression of M cancers and SM cancers : The mean follow-up period of the M cancers was 46 months, and the frequency of progression was 30.0％（from M cancer to SM cancer : 16.7％ ; from M cancer to advanced cancer : 13.3％）, whereas the mean follow-up period of the SM cancers was 23 months, and at a frequency of progression from SM cancer to advanced cancer of 73.3％, the rate of progression of SM cancer was significantly higher（p = 0.001）. There was a wider range of progression periods of M cancer than of SM cancer, and it was concluded that the diversity of growth and progression in early cancers is determined during the M cancer period. （2）Cumulative progression rate of early cancer : The estimated time required for a cumulative progression rate of 50％ was 85 months for M→SM cancer and 31 months for SM→advanced cancer, and the speed of progression from SM cancer to advanced cancer was significantly faster than that of progression from M cancer to SM cancer（p ＜ 0.0001）. （3）Factors affecting progression from M cancer to SM cancer : Cumulative progression rates were compared according to the patients'clinicopathological factors, including age and macroscopic type, but no significant differences were found according to any of the factors. 11 cases in a rapid growth group（RG group）that had progressed in less than 4 years and 15 cases in a slow growth group（SG group）that had not progressed in 4 years or more were selected from among the M cases, the frequency of progression was compared according to clinicopathological factors and the results showed a significantly higher frequency in the SG group of patients with differentiated cancer according to histological type（p＝0.08）. Among those cases the frequency was higher in extremely very well differentiated adenocarcinoma that were mostly that type（p ＜ 0.05）. Based on the above results, it was estimated that the mean time required for progression from M cancer to SM cancer endoscopically is about 7 years, and that the mean time required for progression from SM cancer to advanced cancer is 2～3 years. It was impossible to identify predictive factors for the growth and progression of M cancers based on any of the clinical findings, but the results of the sub-analysis indicated that there may be very slow growth and progression by M cancers with a high degree of differentiation histopathologically.