Are two courses of chemotherapy required in phase II trials in acute leukemia?

In most phase II studies, patients must receive two courses of chemotherapy in order to be judged evaluable for response. We reviewed the experience with six different phase II drugs given to patients with acute leukemia and found that the requirement of a second course may be unnecessary. Administration of second courses do not transform "ineffective" drugs into effective drugs. Furthermore, second courses lead to enhanced toxicity. We conclude that future trials with phase II agents in acute leukemia should be limited to the administration of one course.