多施設共同研究の成績からみた除菌無効胃MALTリンパ腫の特徴と治療

Characteristics and Treatment of Gastric MALT Lymphoma Unresponsive to Eradication Therapy―Special Reference to Multicenter Cooperative Trials

要旨　限局期胃MALTリンパ腫に対してHelicobacter pylori（H. pylori）除菌治療は，第一選択治療として確立されつつあり，50～95％の完全寛解をもたらす．H. pylori陰性例，深部浸潤例，隆起型，t(11;18)転座陽性例，high-grade成分の存在などが除菌無効例の特徴とされているが，無効例に対する二次治療としての放射線療法，化学療法などの有用性も多数報告されている．最近になり，海外で除菌治療についての多施設共同試験の報告もいくつかなされたが，二次治療まで含めた胃MALTリンパ腫の治療体系においてのエビデンスレベルは低い．また，除菌無効例の取り扱い，二次治療の方法と時期，high-grade成分の取り扱い，二次治療としての放射線療法の照射法など不明な点も多い．現在，海外でもいくつかの臨床試験が進行もしくは計画されており，本邦の臨床試験の結果も含めて，その結果に期待したい．

　Eradication of Helicobacter pylori (H. pylori) is considered a well accepted initial therapy in cases of localized low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Cumulative data from several studies have shown that eradication of H. pylori induces complete remission in 50～95％of patients in localized low-grade gastric MALT lymphoma. Complete response is maintained for years in most patients, with about 10％relapse. H. pylori-negative MALT lymphoma, invasion beyond the submucosal layer, protrusion type, translocation t(11;18), or a component of high-grade lymphoma are the main factors that make lymphoma resistant to eradication. Second-line treatment for patients who failed to respond to eradication therapy, including radiotherapy and chemotherapy, resulted in a good response and good survival probability. Recently, there have been some data from multicenter trials about long-term follow-up after eradication therapy, but the evidence level in eradication therapy inclusive of second-line treatment for localized gastric MALT lymphoma is still low. The appropriate duration of observation before diagnosis of treatment failure, appropriate timing and methods of salvage therapy, and management of cases with high-grade components still remain to be defined. At present, multicenter trials, including some in Japan, are under way or are planned, and we look forward to the final results.