Thymus and activation‐regulated chemokine (TARC) as treatment response marker for paediatric Hodgkin lymphoma: A pilot study

Classical Hodgkin lymphoma (cHL) is characterised by malignant Hodgkin Reed–Sternberg cells located in an inflammatory microenvironment. Blood biomarkers result from active cross‐talk between malignant and non‐malignant cells. One promising biomarker in adult patients with cHL is thymus and activation‐regulated chemokine (TARC). We investigated TARC as marker for interim and end‐of‐treatment response in paediatric cHL. In this multicentre prospective study, TARC levels were measured among 99 paediatric patients with cHL before each cycle of chemotherapy and were linked with interim and end‐of‐treatment remission status. TARC levels were measured by enzyme‐linked immunosorbent assay. At diagnosis, TARC levels were elevated in 96% of patients. Plasma TARC levels declined significantly after one cycle of chemotherapy (p < 0.01 vs. baseline) but did not differ at interim assessment by positron emission tomography (p = 0.31). In contrast, median plasma TARC at end of treatment was significantly higher in three patients with progressive disease compared to those in complete remission (1.226 vs. 90 pg/ml; p < 0.001). We demonstrate that, in paediatric patients, plasma TARC is a valuable response marker at end‐of‐treatment, but not at interim analysis after the first two chemotherapy cycles. Further research is necessary to investigate TARC as marker for long‐term progression free survival.