Abstract P060

Clinical relevance of serum TARC levels below 1000 pg/ml in Hodgkin lymphoma: a hidden biomarker?

Background: Serum TARC (Thymus and Activation-Regulated Chemokine) is a specific biomarker for classical Hodgkin lymphoma (cHL), used to monitor tumor volume, clinical course and treatment response. Most clinical studies exclude patients with serum TARC levels below 1000 pg/mL at diagnosis. We aimed to analyse the clinical, histopathological and prognostic characteristics of this specific subgroup and compare them to cases with high (>1000 pg/mL) baseline serum TARC concentrations.

Methods: This retrospective study included 182 cHL patients diagnosed at our institute between 2010 and 2025 who had documented staging serum TARC results. The patterns of clinical stages, EORTC risk categories, and histological subtypes was analysed using Chi-square test. Overall survival (OS) and progression-free survival (PFS) were analysed using the Kaplan-Meier method, both in the total cohort and in subgroups categorized by age.

Results: Low TARC levels (<1000 pg/mL) were detected in 39 patients (21.4%), while 143 patients (78.6%) presented with high levels. The baseline TARC concentrations ranged from 34 to 476,000 pg/mL (median: 27,900 pg/mL). Highly significant correlations were observed between TARC distribution and clinical stages (p<0,001), with low TARC being prominent in stage I and high TARC dominating in further (II-IV) stages. A significant correlation was also observed with EORTC risk categories (p=0.0139), where the early favourable subgroup showed the highest prevalence of low TARC levels (43.4%). The distribution of histological subtypes significantly differed (p<0.0001): the lymphocyte-rich subtype was predominant in the subgroup with low TARC levels, while a predominance of nodular sclerosis was observed at high serum levels. In the total cohort, no significant differences were found in OS or PFS (p=0.75 and p=0.547). However, when analysed by age, patients under 60 years with low baseline TARC levels showed a significantly improved PFS compared to the high TARC group (p=0.048). Conversely, no prognostic value was observed in patients over 60 years (p=0.939).

Conclusion: Our findings confirm that the diagnostic value of serum TARC remains relevant below 1000 pg/mL, as it reflects tumor burden, risk stratification, and unique histopathological features. For patients under 60 years of age, low TARC levels at diagnosis can be an indicator of favourable prognosis. Therefore, integrating this commonly excluded subgroup into future studies is highly recommended.