High-dose chemotherapy followed by autologous transplantation may overcome the poor prognosis of diffuse large B-cell lymphoma patients with MYC/BCL2 co-expression

The concurrent expression of MYC and BCL2 on immunohistochemistry (IHC) ('double expressor') is recently emerging as one of the strongest and most unfavorable prognostic factor for diffuse large B-cell lymphoma (DLBCL). 1 – 5 Nevertheless, the higher prevalence of older patients, together with the association between double expressor DLBCL and advanced age, may have represented a potential confounding factor affecting the conclu-sions of all these studies. In fact, older DLBCL patients generally have inferior outcome due to the higher risk of adverse events and dif ﬁ culties to perform high-dose salvage therapies. 6 This potential age bias was strongly suggested by a recent German study that included only young DLBCL patients at diagnosis, and did not con ﬁ rm the negative prognostic effect of the double expressor phenotype after either eight cycles R-CHOEP-14 or sequential high-dose therapy followed by autologous stem cell transplant (ASCT). 7 This discordant result may be explained by either the lower prognostic relevance of MYC/BCL2 among young DLBCL patients, and by the ability of intense chemotherapy regimens to overcome the negative prognostic value of MYC/BCL2 co-expression. In order to investigate these hypotheses, we analyzed the MYC and BCL2 co-expression clinical impact on a consecutive series of 140 DLBCL patients, 71 at diagnosis and 69 at ﬁ rst relapse, respectively. All patients were treated with intense chemotherapy programs oriented to ﬁ nal ASCT consolidation between 2003 and 2015 at the Istituto Nazionale dei Tumori Milano. Seventy-one naïve DLBCL patients (51%) were treated in ﬁ rst line with high-dose sequential chemotherapy integrated with monoclonal antibody Rituximab

The concurrent expression of MYC and BCL2 on immunohistochemistry (IHC) ('double expressor') is recently emerging as one of the strongest and most unfavorable prognostic factor for diffuse large B-cell lymphoma (DLBCL). [1][2][3][4][5] Nevertheless, the higher prevalence of older patients, together with the association between double expressor DLBCL and advanced age, may have represented a potential confounding factor affecting the conclusions of all these studies. In fact, older DLBCL patients generally have inferior outcome due to the higher risk of adverse events and difficulties to perform high-dose salvage therapies. 6 This potential age bias was strongly suggested by a recent German study that included only young DLBCL patients at diagnosis, and did not confirm the negative prognostic effect of the double expressor phenotype after either eight cycles R-CHOEP-14 or sequential high-dose therapy followed by autologous stem cell transplant (ASCT). 7 This discordant result may be explained by either the lower prognostic relevance of MYC/BCL2 among young DLBCL patients, and by the ability of intense chemotherapy regimens to overcome the negative prognostic value of MYC/BCL2 co-expression. In order to investigate these hypotheses, we analyzed the MYC and BCL2 co-expression clinical impact on a consecutive series of 140 DLBCL patients, 71 at diagnosis and 69 at first relapse, respectively. All patients were treated with intense chemotherapy programs oriented to final ASCT consolidation between 2003 and 2015 at the Istituto Nazionale dei Tumori Milano. Seventy-one naïve DLBCL patients (51%) were treated in first line with high-dose sequential chemotherapy integrated with monoclonal antibody Rituximab (R-HDS; Supplementary Figure S1). 8,9 Eligibility to this intense approach was decided considering either the high international prognostic index (IPI) score or the extended nodal and extranodal disease. The second cohort was composed by 69 (49%) DLBCL patients in first relapse after chemo-immunotherapy regimens and treated with intense salvage programs, including 53 (77%) treated with R-HDS and 16 (23%) with CORAL-like treatment (R-ICE/R-DHAP as induction chemotherapy before transplant), respectively. 10 The patients' median age was 60 years (range, 30-76); 48 patients (34%) were older than 60 years, but all were considered fit and eligible for intense chemotherapy and transplant consolidation. The median follow-up of the whole series was 83 months (range 2-200). All pathological revisions and IHC colorations were performed as described in Supplementary Material and Methods and Supplementary Table S1. 11 All statistical analyses were performed using appropriate scripts in R software (www.r-project.org; Supplementary Material and Methods).
In order to detect the real 'double hit' DLBCL patients, FISH analysis was performed only on 52/65 (80%) MYC IHC-positive patients. MYC rearrangements was detected in 8/52 (15%) patients and among them only one also harbored a BCL2 rearrangement, being classified as 'double hit' DLBCL. [1][2][3][4][5]12 Except for a slightly higher prevalence of patients with Eastern Cooperative Oncology Group (ECOG) score ⩾ 2 among nondouble expressor patients, no other significant clinical differences were observed between two groups ( Table 1). The overall response rate to high-dose therapy was 67% (n = 94), and 59% (n = 82) of all patients were transplanted according with treatment program. Sixty-eight (82%) of these were in CR at the time of transplant. Fifty-eight (41%) patients were not able to receive planned ASCT for refractory disease (n = 47, 33%), poor mobilization (n = 3; 2%), concurrent infections and/or toxic complications (n = 7; 4.3%) or patient's preference (n = 1; 0.7%). Double expressor patients did not show any higher prevalence among patients that were not transplanted considering either all patients and naive and relapsed series separately (Table 1). Myeloablative conditioning regimens were high-dose chemotherapy schedules in 63 patients (77%) and high-dose 90Y-Ibritumomab Tiuxetan in 19 (23%), respectively. 13 Except for older age and ECOG score ⩾ 2, no clinical and outcome differences were observed between the two groups (Supplementary Table S2).
Overall, results of this study suggest that standard high-dose therapy and final transplant consolidation may abolish the poor prognostic value associated with MYC/BCL2 co-expression among young and/or fit DLBCL patients both in first line and first relapse. As expected the clinical outcome of transplanted and no transplanted patients was significantly different, but this was not influenced by MYC/BCL2 co-expression (Supplementary Figure S3). This suggests that MYC/BCL2 co-expression is not directly involved in refractoriness and resistance to intensive salvage therapy Although the cutoff of ⩾ 40% for MYC positivity in IHC is widely accepted, 14 different BCL2 cutoffs were used to define double expressor patients. 1,4 For this reason, all analyses described above were repeated using the alternative BCL2 cutoff described by Johnson et al. (⩾50%), 4 and all results were confirmed (data not shown).
In our series we found a significant lower prevalence of double hit DLBCL patients compared with other series. [1][2][3][4][5]7,12 This discrepancy could be due to the limited series size and to the known low prevalence of double hit DLBCL among young patients. 1,3,4,12,15 For this reason our findings are not applicable on this distinct and aggressive biological entity.
Future incorporation of novel agents into first-line regimens may improve the efficacy and safety of intense chemotherapy regimens such as R-HDS program, therefore improving the final outcome.