Appropriate dose reduction in induction therapy is essential for the treatment of infants with acute myeloid leukemia: a report from the Japanese Pediatric Leukemia/Lymphoma Study Group

Tomizawa, Daisuke; Tawa, Akio; Watanabe, Tomoyuki; Saito, Akiko Moriya; Kudo, Kazuko; Taga, Takashi; Iwamoto, Shotaro; Shimada, Akira; Terui, Kiminori; Moritake, Hiroshi; Kinoshita, Akitoshi; Takahashi, Hiroyuki; Nakayama, Hideki; Kiyokawa, Nobutaka; Isoyama, Keiichi; Mizutani, Shuki; Hara, Junichi; Horibe, Keizo; Nakahata, Tatsutoshi; Adachi, Souichi

Infants (<1 year old) with acute myeloid leukemia (AML) are particularly vulnerable to intensive cytotoxic therapy. Indeed, the mortality rate was high among infants enrolled in the Japanese Pediatric Leukemia/Lymphoma Study Group AML-05 study, which prompted us to temporarily suspend patient enrollment and amend the protocol. Forty-five infants with AML were enrolled. For patients aged <2 years, drug doses were adjusted for body weight. Following the protocol amendments, doses for infants were reduced by a further 33 % in the initial induction course. Six infants died during the induction phase (including five early deaths), mainly due to pulmonary complications. The 3-year probability of overall survival (pOS) in all 45 infants [55.9 %, 95 % confidence interval (CI) 37.9–70.6 %] was significantly lower than that of patients aged 1 to <2 years (77.0 %, 95 % CI 62.7–86.3 %) and those aged ≥2 years (74.7 %, 95 % CI 69.2–79.4 %) (P = 0.037), mainly due to the higher non-relapse mortality rate in infants. No early deaths occurred after the protocol amendments, and the 3-year pOS of the 17 infants enrolled thereafter was 76.4 % (95 % CI 48.8–90.4 %). In conclusion, appropriate dose reduction is essential to avoid early deaths when treating infants with AML.