Clinical and Molecular Significance of Tumor Necrosis In Newly Diagnosed Patients with Hodgkin's Lymphoma and Diffuse Large B Cell Lymphoma

Abstract 1995

Lymphoma of various types in newly diagnosed patients may exhibit necrotic areas in the tumor mass on imaging. To date, little is known about the clinical significance of this finding and even less is known about the mechanism of cell death in the necrotic tissue - apoptosis, molecular necrosis or autophagy.

The objective of this study was to investigate the prognostic significance of tumor necrosis in newly diagnosed Hodgkin's lymphoma (HL) and diffuse large B cell lymphoma (DLBCL) patients and to define the molecular mechanism of cell death responsible for the necrosis.

Two hundred and four CT scan or CT-PET studies from newly diagnosed patients with DLBCL (131) and HL (73) were analyzed for the presence of tumor necrosis. Radiographic appearance of necrosis was present in 47% of all patients, 34% HL and 53% DLBCL.

A statistically significant correlation was found between necrosis and bulky disease (tumor mass size≥10 cm) (p=0.0002×10^-6) and also between necrosis and elevated LDH (p=0.00002) (see Table 1).

No statistically significant correlation was found between necrosis and age >60 or more advanced stage of disease. There was also no statistically significant difference in interim response to treatment, disease-free survival and overall survival between patients with necrosis and without it.

Our results show that in contrast to solid tumors, tissue necrosis in lymphoma is not a predictor of worse prognosis: though more patients with radiographic appearance of necrosis had also the known bad prognostic signs- elevated LDH and/or bulky disease, this group did not have worse outcome. We suggest that necrosis can lead to a better response to treatment in lymphoma.

Among 56 HL and DLBCL patients that underwent an open surgical biopsy of the tumor mass nineteen presented necrotic morphology in the biopsied tissues: 8 HL and 11 DLBCL. Biopsies without evidence of necrotic morphology (10 patients from the above 56) and reactive lymph nodes (4) were included as controls. All sections were stained for ki-67 (proliferation marker), activated caspase-3 (apoptosis marker) and HMGB-1 (necrotic cell death marker).

DLBCL cells showed high proliferation rate, with ki-67 index ranging from 40 to 90% and in HL cells the ki-67 index ranged from 5 to 50%. All the samples positive for HMGB-1 were from patients with HL and 10/11 of activated caspase-3 positive samples were from DLBCL. These results show a differential molecular mechanism of cell death in the tumor mass of newly diagnosed HL and DLBCL patients.

The constitutive activation of the survival factor Nuclear Factor-kB (NF-κB) was found in Hodgkin and non-Hodgkin lymphoma. We stained the same biopsies for p65/RelA and examined the nuclear localization of NF-κB as an indication for activation of the NF-κB pathway. Four DLBCL and 4 HL samples were positive for NF-κB activity. Nevertheless, we found that activation of caspase-3 and/or HMGB-1 induced cell death in these tissues.

In summary, tumor necrosis in HL and DLBCL is correlated with bulky disease and high LDH, yet is not correlated with prognosis. The molecular mechanism of cell death differs between the two types of lymphoma.