Treatment with the ALK-inhibitor crizotinib produced high response rates in pediatric patients with ALK-positive anaplastic large cell lymphoma (ALCL) and inflammatory myofibroblastic tumors (IMTs), according to phase 2 trial results.

“The robust and sustained clinical responses to crizotinib in patients with relapsed or refractory ALK-driven ALCL and IMT highlight the importance of this oncogene and the sensitivity to ALK inhibition in these diseases,” said Yaël P. Mossé, MD, of Children’s Hospital of Philadelphia, and her associates.

Twenty-six patients with recurrent ALCL and 14 with unresectable IMTs – not older than 22 years – were enrolled. Six of the ALCL patients were treated at 165 mg/m2 (ALCL165) and 20 at 280 mg/m2 (ALCL280), which was found to be the recommended phase 2 dose. Ten of the ALCL280 patients had been treated at an equivalent to this dose in phase 1 and they were included in the phase 2 analysis. Those in the ALCL280 group tended to be older, at a median age of 12.2 years, than the other patients in the study, the investigators reported (J Clin Oncol. 2017 Aug 8 doi: 10.1200/JCO.2017.73.4830 ).

Eight of the IMT patients were enrolled in a dose-escalation portion of the study, with one receiving a 100 mg/m2 dose, one receiving 165 mg/m2, and the other six receiving 280 mg/m2. The other six were treated at 280 mg/m2. All of the IMT patient results are presented as one pool because those at the lower doses had toxicity and responses similar to those in patients given the higher dose.

Sixteen of 20 patients in the ALCL280 group – 80% – had a complete response, two had a partial response, and two were found to have stable disease. The median duration of treatment in this group was 0.4 years, and the median time to the first partial or complete response was 27 days. In the ALCL165 group, five of six, or 83%, had a complete response, along with one found to have stable disease. This group had a median treatment duration of 2.79 years, and the median time to the first partial or complete response was 26.5 days.

In the IMT group, 5 of 14, or 36%, had a complete response; 7, or 50%, had a partial response, and 2 had stable disease. They received treatment for a median of 1.63 years, and the median time to the first partial or complete response was 28.5 days.

Investigators reported that at least one grade 3 or 4 adverse event occurred in 83% of patients in the ALCL165 group, in all of the patients in the ALCL280 group, and in 71% in the IMT group. Adverse events considered possibly, probably, or definitely related to the study treatment occurred in 33% of the ALCL165 group, in 85% of the ALCL280 group, and in 57% of the IMT group. The most common adverse event was a decreased neutrophil count.

“Notable objective and sustained responses were observed in patients with ALK fusion-positive ALCL and IMT,” the investigators wrote, “establishing a precedent in pediatric oncology for studying the early-phase activity of a targeted agent in a biomarker-selected and histology-independent cohort of patients.

“In the cohort of patients with ALK-positive unresectable IMTs,” they continued, “ALK inhibition was a highly effective therapy and supports consideration of frontline therapy with crizotinib, a strategy that could also be relevant to adults with this rare disease.”