Some DLBCL patients would relapse within the first two or three years after diagnosis, and late relapse that occurred after five years was less common[11]. To screen out patients prone to relapse at the first diagnosis was a hot spot in clinical research. Although significant achievements had been made in studying prognostic markers of novel DLBCL, and the nomogram had been validated as a useful tool for predicting overall survival (OS) with higher sensitivity and accuracy than IPI system[7] the recurrence-related risk factors of DLBCL and the nomogram models for recurrence risk assessment needed to be further explored.
In this study, we focused on those widely concerning parameters in daily clinical and pathological work and found that relapsed DLBCL had some special characteristics. Patients with relapsed DLBCL were more likely to be of non-GCB type, and have advanced Ann Arbor stage (III-IV), advanced IPI score (3–5), advanced NCCN-IPI score, higher ECOG score (2–4), elevated LDH, β2-MG and CRP level. The lesions tended to originate from nodal, with IHC showed CD10-negative, BCL6-negative and BCL2-positive.
We further identified two independent predictors: positive BCL2 expression, advanced Ann Arbor stage and elevated LDH level. Ann Arbor stage, a member of IPI system using for prognostic evaluation, could affect the PFS and OS of DLBCL. There were also many previous studies to explore the relationship between Ann Arbor stage and lymphoma recurrence. Yusuke Kanemasa et al. [12]found that advanced Ann Arbor stage (III-IV) was significantly associated with central nervous system (CNS) relapse, and could distinguish the low- and high-risk groups when combined with albumin level, number of extranodal sites, and involvement of retroperitoneal lymph node. Kerry J Savage[13] once again emphasized the significance of Ann Arbor stage in predicting CNS recurrence in 2017. In Philipp Schommers’s study[14], advanced Ann Arbor stage was also an independent risk factor for relapses in HIV-associated non-Hodgkin lymphoma. Our research further confirmed the role of advanced Ann Arbor stage in DLBCL recurrence.
As a key regulator in cell apoptosis, dysregulation of BCL2 caused by chromosome translocation, gene amplification, or activation of the NF-κB signal pathway could promote the occurrence and development of B-cell lymphoma[15]. BCL2 overexpression was associated with drug resistance and poor prognosis[16], and could be inhibited by Venetoclax in many hematological cancers[17]. Naoko Tsuyama et al. [18]found that DLBCL patients with BCL2 overexpression had a lower rate to obtain CR, a higher probability of recurrence after CR, and a worse 3-year PFS rate. What’s more, DLBCL with coexpression of MYC and BCL2 protein (so-called double-expressor lymphoma, DEL) was considered to have adverse outcomes and increased risk of CNS recurrence[19]. Since there was little information regarding the MYC protein expression in consultation cases in our study, the relationship between the co-expression of BCL2 and MYC and the recurrence of DLBCL was unknown. But we did find that positive BCL2 expression was a significant independent risk factor for DLBCL recurrence, which was consistent with that in previous studies.
The elevated LDH level could also promote the relapse of DLBCL in this study. LDH, a valuable biomarker, could be easily measured in clinical and hospital laboratories. As its elevation was mostly associated with high tumor burden and adverse clinical behavior, LDH level was of great prognostic effect on solid tumors, in particular melanoma, prostate and renal cell carcinomas[20], and was also widely used as one of the independent prognostic factors in IPI system and other prognostic nomogram models in aggressive B-cell lymphomas[7, 21, 22]. In terms of DLBCL, elevated LDH level at initial diagnosis was found to be related to the increased risks of CNS relapse[23, 24]. Compared with patients with late relapses, patients with early relapses were more likely to have a higher LDH level, higher IPI score and adverse stage (III-IV)[25]. In Huang’s study, univariate analysis also indicated that LDH > 1000U/L was one of the relapse risk factors of pediatric mature B cell lymphoma[26].
The final nomogram consisted of 3 predictors: Ann Arbor stage, BCL2 expression, and LDH level, so we called it “ABL-nomogram”. Based on the data in our study, this newly recurrence-risk predicted nomogram had a higher C-index than IPI system and NCCN-IPI system. And the ROC curves and calibration plots also demonstrated that ABL-nomogram had a good level of discriminative ability and accuracy. What’s more, according to the points calculated from ABL-nomogram, DLBCL patients could be well divided into four subgroups with significant differences in recurrence risk (P < 0.001). Patients in G4 subgroup with adverse Ann Arbor stage (III-IV), elevated LDH level and positive BCL2 expression had the highest recurrence risk, while patients in G1 subgroup with none of these three risk factors had the lowest recurrence risk. It meant that ABL-nomogram had a good ability to assist risk stratification.
As far as we know, the ABL-nomogram was the first nomogram model constructed for predicting DLBCL recurrence based on clinical and pathological characteristics. The model not only performed better than IPI and NCCN-IPI, but also used economically accessible indicators for risk stratification. It could be used to assess the recurrence risk of each DLBCL patient before treatment, so as to formulate personalized treatment to improve the prognosis. However, this study had some limits. Firstly, as a retrospective study, there was a certain bias in patients’ selection. Secondly, due to the sample size limitation, this study lacked external validation. Thirdly, although patients received R-CHOP-like chemotherapy, the effects of dosage and other adjuvant treatments on the prognosis were not explored. Lastly, this model had not yet included molecular factors. We would try to realize multi-center prospective research to expand the sample size and control confounding factors, and incorporate more novel biomarkers for further improving this nomogram model and verifying its feasibility in future studies.