Clinical Significance of Tumor-Associated Macrophages in Early-Stage Hodgkin's Lymphoma.

Abstract 2638

Although patients with early-stage Hodgkin's lymphoma (HL) overall have a high rate of cure, they cannot be considered as a homogeneous group. In fact, a portion of these patients are resistant to or may relapse after standard treatment. Current prognostic criteria based on clinical and laboratory parameters at diagnosis do not allow to accurately identify the subset of patients with less favorable clinical outcome. In a study aimed at defining new biomarkers for risk stratification, an increased number of tumor-associated macrophages was found to be strongly associated with shortened survival in patients with classic Hodgkin's lymphoma [N Engl J Med. 2010 Mar 11;362(10):875-85].

The aim of this study was to evaluate the clinical significance of the proportion of CD68-positive infiltrating macrophages in patients with early-stage Hodgkin's lymphoma. By using an immunohistochemistry method, we analyzed diagnostic biopsies of 63 patients followed at our institution between 2006 and 2010, and uniformly treated with ABVD (adriamycin, bleomycin, vinblastine, dacarbazine) chemotherapy. Thirty-nine (62%) patients were males and 24 (38%) were females; median age at diagnosis was 30 years (range 17–85). Histological subtype was nodular sclerosis HL in 55 cases, mixed cellularity HL in 3 cases, lymphocyte-rich HL in 3 cases, and not classified in 2 cases. Five patients had subdiaphragmatic disease while 58 had supradiaphragmatic localizations. Forty-four patients with supradiaphragmatic disease were classified in the EORTC unfavorable subset: in detail, 25 patients had B symptoms and ESR ≥30, or ESR ≥50 despite the absence of B symptoms, 29 patients had bulky disease, 7 patients were older than 50 years, and 6 patients had more than 3 nodal areas involved. Thirty-six out of 63 (59%) patients received radiotherapy as a consolidation treatment after chemotherapy. After completion of the therapeutic program, 54 out of 63 (86%) patients obtained complete remission, while 9 (14%) had refractory disease; 15 out of 54 (28%) patients in complete remission relapsed during follow up.

Diagnostic biopsies were reviewed by expert hematopathologists and classified into 3 groups according to the intensity of CD68 expression [N Engl J Med. 2010 Mar 11;362(10):875-85]. CD68-positive infiltrate was lower than 5% in 14 patients (group A), between 5 and 25% in 43 patients (group B), and greater than 25% in 6 patients (group C).

Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method with observation time calculated from diagnosis. Comparison between survival curves was performed by means of the Gehan-Wilcoxon test. The 2-year OS and PFS in the entire cohort were 98% and 79%, respectively. There was a difference in the 2-year PFS between patients with favorable and those with unfavorable prognosis according to the EORTC risk criteria (100% vs 72%, P<.05). CD68 expression had a significant effect on 2-year PFS, which was 86%, 84% and 33% in group A, B and C, respectively (P<.004). After merging group A and B, there was a significant difference in 2-year PFS between patients having up to 25% and those with more than 25% CD68-positive infiltrating macrophages (84% vs 33%, P<.002). All patients with favorable EORTC criteria had CD68 expression lower than or equal to 25%. Within those with unfavorable EORTC criteria, patients with CD68 expression greater than 25% had a worse 2-year PFS compared with patients having values up to 25% (33% vs 77%, P<.012).

In conclusion, the findings of this study suggest that a proportion of CD68-positive infiltrating macrophages greater than 25% is associated with unfavorable clinical outcome in patients with early-stage Hodgkin's lymphoma. However, for CD68 expression to be used as a prognostic factor in these patients, both technical standardization of the immunohistochemistry method and prospective validation of the prognostic biomarker in a clinical trial are clearly required.