南予医学雑誌　第18巻

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鹿田、他：Successful resolution of relapsed MPAL with t(9;22)(q34.1;q11.2);BCR-ABL1 with ponatinib and prednisolone南予医誌　Vol.18　No. １　2017－79－hematological CR， but after ３ months of dasatinib administration he suffered relapse of lower gastrointestinal bleeding， sug-gesting intolerance to dasatinib．Around the same time， ponatinib became available for use， and therefore in November 2016， the patient was switched from dasatinib to ponatinib（45㎎/day）with prednisolone （10㎎/day）after recovery from lower gastrointestinal bleeding．After １ month of ponatinib and prednisolone treatment， the patient achieved molecular CR（mCR）， which was maintained for ７ months with-out serious adverse effects．DiscussionHere we have documented a case of re-lapsed Ph+MPAL in which dasatinib was discontinued due to lower gastrointestinal bleeding and subsequently treated suc-cessfully with ponatinib and prednisolone．MPAL has been reported to have a poor prognosis in comparison with AML and ALL１，２，11）．According to Wolach’s１）review which summarized newly diagnosed MPAL cases meeting the current WHO diagnostic criteria， the CR rate was 61.5-85.2％ and the median survival was 14.8-18 months．Mat-utes et al．２）reported that advanced patient age， Ph+， and an AML regimen were cor-related with poor prognosis．Therefore， an ALL regimen would seem to be preferable．However， only a few examples of MPAL patients treated with TKIs were included in those reports．On the other hand， some reports have documented that addition of TKIs to chemotherapy improved the treat-ment outcome in patients with newly diag-nosed Ph＋MPAL， and that there were no significant differences in CR rates and sur-vival after imatinib-containing chemotherapy between newly diagnosed Ph＋MPAL and Ph＋ ALL in the TKI era４，５）．Aside from these reports， Takata et al．６）have reported that dasatinib and prednisolone led to mCR in elderly patients with newly diagnosed MPAL， and considered that this could be a treatment option especially for elderly patients with newly diagnosed MPAL who would not be candidates for standard induc-tion chemotherapy．These reports suggest that TKIs may play an important role in im-proving the survival of patients with newly diagnosed Ph+MPAL， and that TKI alone or with ALL-type chemotherapy would be suitable for such patients．On this basis， we treated our patient with TKI in combination with ALL-like chemotherapy．Even though TKIs have improved the treat-ment outcome of patients with newly diag-nosed Ph＋ALL and MPAL， they still show much higher rates of relapse than those with CML．This is mainly due to BCR-ABL TKD mutations， such as the T315I muta-tion that is resistant to all currently avail-able TKIs other than ponatinib， and P-loop mutations８，12）．Although BCR-ABL TKD mutation can be detected only at low levels at the time of diagnosis， it can be detected in 67-90％ of patients with Ph＋ALL who suffer relapse after administration of ima-tinib or dasatinib plus chemotherapy７，８，12）．It seems likely that this relapse mechanism may also occur in patients with Ph＋MPAL．