Introduction: Classical Hodgkin lymphoma (HL) is characterized by a complex, increasingly understood microenvironment which is considered crucial for survival and proliferation of the malignant Hodgkin and Reed-Sternberg cells (HRSC). HLA expression is a key component for immune cell interaction and thereby microenvironment composition. Additionally, we and others have shown that a low B-cell content is a negative prognostic factor in advanced-stage HL which can be assessed quantitatively by digital pathology using slides generated for diagnostic purposes (Jachimowicz 2021). Herein we aimed to assess HLA expression status and the prognostic relevance of B-cell content in early-stage unfavorable HL.
Patients and methods: We analyzed primary tumor biopsies of patients with newly diagnosed early-stage unfavorable HL either treated with 4xABVD or 2xBEACOPPesc followed by 2xABVD within the GHSG HD14 trial, each consolidated by 30Gy involved-field radiotherapy (von Tresckow 2012). Our project cohort was enriched for patients suffering from disease progression or relapse (20.2% vs 6.2% in the total HD14 population). Whole-slide image analysis of CD20 staining was performed using TissueStudio 64 (Definiens) to quantify the B-cell content. Immunohistochemistry for ß-2-Microglobulin (HLA-I) and HLA-DP (HLA-II) was scored by visual inspection on HRSC.
Results: Major clinical variables such as sex, age, B-symptoms, GHSG risk factors and histological subtypes did not differ significantly between the project cohort (N=198) and HD14 trial population (N=1889). HLA-I and -II were expressed on HRSC in 13.3% and 49.1% of cases, respectively. Only 8.3% of cases showed positivity for both HLA-I and -II, while 45.8% were double-negative. Median B-cell content was lower in HLA-I negative (12.8% vs 18.5%, p=0.0168) and double-negative cases (11.5% vs 18.1% in double-positive cases, p=0.0392). A low B-cell content was associated with unfavorable outcome: 5-year PFS estimates are 70.6% and 83% for subjects with low (<=8%) or high (>8%) B-cell content (Figure 1, log-rank p=0.08). A stepwise multivariate analysis including type of treatment confirmed B-cell content as the only significant risk factor for PFS (p=0.0196).
Conclusions: HLA expression is variable in early-stage unfavorable HL and associated with B-cell content. Similarly to advanced-stage HL, a low B-cell content measured by digital pathology of routinely available diagnostic slides is associated with unfavorable outcome.