Reply: Interim PET in Hodgkin Lymphoma: Is It So Useless?

Circulating tumor DNA in Hodgkin lymphoma

Somatic mutations of genes involved in NF-κB, PI3K/AKT, NOTCH, and JAK/STAT signaling pathways play an important role in the pathogenesis of Hodgkin lymphoma (HL). HL tumor cells form only about 5% of the tumor mass; however, it was shown that HL tumor-derived DNA could be detected in the bloodstream. This circulating tumor DNA (ctDNA) reflects the genetic profile of HL tumor cells and can be used for qualitative and quantitative analysis of tumor-specific somatic DNA mutations within the concept of liquid biopsy. Overall, the most frequently mutated gene in HL is STAT6; however, the exact spectrum of mutations differs between individual HL histological subtypes. Importantly, reduction of ctDNA plasma levels after initial treatment is highly correlated with prognosis. Therefore, ctDNA shows great promise as a novel tool for non-invasive tumor genome analysis for biomarker driven therapy as well as for superior minimal residual disease monitoring and treatment resistance detection. Here, we summarize the recent advancements of ctDNA analysis in HL with focus on ctDNA detection methodologies, genetic profiling of HL and its clonal evolution, and the emerging prognostic value of ctDNA.

SUVmax-based assessment of PET response shows a superior specificity to Deauville criteria for predicting recurrence in Hodgkin's lymphoma

One of the limitations of ¹⁸FDG PET/CT for therapeutic evaluation in Hodgkin's Lymphoma is the relatively high rate of false positive uptake. SUV_max reduction (ΔSUV_max) and tumor/liver ratio (TLr) are promising tools for response assessment in lymphoma. We determined the optimal cutoff values for ΔSUV_max and TLr and compared them to Deauville score (DS) after two and four cycles chemotherapy (PET2 and PET4 respectively) and at the end of treatment PET (PETeot) on a cohort of 362 patients. TLr showed better diagnostic performances than DS for predicting 5-year progression-free survival (PFS), especially on early PET/CT assessments. Positive predictive values at PET2 for TLr, ΔSUV_max and DS were 51%, 34% and 31% respectively. On the multivariable analysis, significant predictive factors of PFS were TLr (at PET2, PET4 and PETeot) and ΔSUV_max (at PET4 and PETeot). DS was not significantly associated with PFS at any PET timing.