Plasma thymus and activation‐regulated chemokine (TARC) as diagnostic marker in pediatric Hodgkin lymphoma

Pediatric classical Hodgkin's lymphoma (cHL) is characterized by Hodgkin Reed‐Sternberg cells located in an inflammatory microenvironment. Blood biomarkers result from active crosstalk between these cells. One promising biomarker in adult cHL patients is “thymus‐and‐activation‐regulated chemokine” (TARC). The objectives of this study were to define normal TARC values in non‐cHL children and to investigate and correlate pretherapy TARC as diagnostic marker in pediatric cHL. In this multicenter prospective study, plasma and serum samples were collected of newly diagnosed cHL patients before start of treatment (n = 49), and from randomly selected non‐cHL patients (n = 81). TARC levels were measured by enzyme‐linked immunosorbent assay. The non‐cHL patients had a median plasma TARC value of 71 pg/mL (range: 18‐762), compared to 14 619 pg/mL (range: 380‐73 174) in cHL patients (P < .001). TARC values had a high discriminatory power (AUC = .999; 95% confidence interval, .998‐1). A TARC cutoff level of 942 pg/mL maximized the sum of sensitivity (97.9%) and specificity (100%). TARC plasma levels were associated with age, treatment level, bulky disease, B‐symptoms, and erythrocyte sedimentation rate. TARC was found to be a highly specific and sensitive diagnostic marker for pediatric cHL. This noninvasive marker could be of great value as screening test in the work‐up for pediatric patients with lymphadenopathy.