ALK and anaplastic large cell lymphoma: When only prospective studies included in the meta-analysis of CR were examined, PTCL as a whole group demonstrated substantial heterogeneity (I2 = 69%), AITL, ALK-negative ALCL, and NK/T demonstrated no evidence of heterogeneity (all I2 = 0%), and ETTL demonstrated moderate heterogeneity (I2 = 50%).