[Challenges of international collaborative clinical trials in Asia].

Clinical trials with a solid strategy are indispensable for improving outcomes of rare childhood leukemias such as infant acute lymphoblastic leukemia (ALL) and ALL associated with Down syndrome, and international collaboration contributes to trial success. I am part of a group conducting an international trial of ALL associated with Down syndrome in collaboration with Asian countries. Although we are meeting enrollment targets, there have been no enrollments outside Japan. We also planned a clinical trial in unclassifiable acute leukemia, but abandoned this effort due to a lack of consensus on the choice of treatment regimen. Many elements must fit together for an international trial to succeed, including not only the study's concept, theme, and objectives, but also the organization, the logistics, and, ultimately, trained professionals to carry it out. At the same time, of course, there is the need for appropriate timing and luck. International trials across countries with different cultures, social organizations, and medical systems require persistent effort and negotiation skills. Professional training and infrastructure development are necessary to make this possible.