Nov 20, 2019
This podcast summarizes the findings of the Lunenburg Lymphoma Biomarker Consortium systematic evaluation of MYC rearrangements in DLBCL, and discusses the prognostic impact of MYC, BCL2 and BCL6 rearrangements, and implications for FISH testing in newly diagnosed DLBCL.
TRANSCRIPT
This JCO Podcast provides observations and commentary on the JCO article “Prognostic Significance of MYC Rearrangement and Translocation Partner in Diffuse Large B-Cell Lymphoma - A Study by the Lunenburg Lymphoma Biomarker Consortium” by Rosenwald et al. My name is Jeremy Abramson, and I am an attending physician at the Massachusetts General Hospital and an Associate Professor of Medicine at Harvard Medical School. My oncologic specialty is lymphoma.
MYC rearrangements occur in approximately 10% of diffuse large B-cell lymphomas and have been associated with a worse prognosis. When the MYC translocation occurs in concert with translocations of BCL2, BCL6, or both, initial series have suggested particularly poor outcomes with few patients achieving long term survival with conventional therapies. This entity has been classified in the current WHO classification as high-grade B-cell lymphoma with rearrangements of MYC and BCL2 and/or BCL6 and is more conventionally known as double (or triple) hit lymphoma. Though initial series painted a grim prognosis for these patients, more recent larger series have suggested that approximately 40% of double hit lymphoma patients may be cured, and that outcomes may be improved with more intensive regimens such as dose-adjusted EPOCH-R. Most of these published series to date, however, continue to be limited by significant selection bias whereby cases with the most aggressive clinical or histopathologic features are likelier to be tested for MYC translocations, thus potentially excluding more prognostically favorable patients. The small size of series to date has also made it difficult to assess more granular questions in MYC translocated diffuse large B cell lymphoma, hereafter referred to as DLBCL, such as the prognostic impact of MYC translocations when occurring without other translocations, the impact of translocation partner with MYC (Ig or non-Ig gene locus) in double hit lymphoma, and the significance of MYC/BCL6 double hit lymphomas which are far less common than MYC and BCL2. Another practical question is who should we be testing for MYC translocations in the first place? Do we need to test every new case of DLBCL? Or should we routinely test only an enriched population, such as those with MYC protein expression by immunohistochemistry, or GCB-like DLBCLs, which include the majority of double hit lymphomas?
In the article that accompanies this podcast, the Lunenberg Lymphoma Biomarker Consortium presents the single largest and most systematic analysis to date of MYC translocations in DLBCL, and sheds significant light on many of the most outstanding questions in this population. The Consortium studied over 2000 cases of DLBCL with available tissue and clinical data, drawn from large prospective cooperative group studies as well as population-based registries in Canada, the United Kingdom and the United States. The median age of the cohort was 66 years, and the median follow up was mature at greater than 6 years. All patients were treated with R-CHOP or R-CHOP-like therapy. MYC rearrangements were found in 11% of patients. One third of these occurred as a sole rearrangement, 39% in concert with a BCL2 rearrangement, 15% with a BCL6 rearrangement, and 12% with both (i.e. triple hit lymphoma).
Patients with MYC rearrangements had higher risk features by the IPI score than the entire DLBCL population, and patients with double/triple hit lymphoma had higher clinical risk factors than patients with MYC rearrangements alone. Patients with double or triple hit lymphoma had a significantly inferior outcome in terms of both progression free and overall survival compared to the overall DLBCL cohort, while no negative prognostic impact was conferred by a MYC translocation alone. Notably, the prognostic impact was only observed in the first 2 years from diagnosis. They also compared the 31 MYC/BCL6 double hit patients with 82 MYC/BCL2 double hits, and found similar outcomes in the groups, validating that MYC/BCL6 double hit lymphomas should be considered high risk along with their BCL2 translocated counterparts. Prognosis for triple hit lymphoma was no worse than double hit lymphoma. Perhaps most striking, however, was how well double and triple hit lymphoma patients did when compared to previously published retrospective studies. In this comprehensive evaluation by the Consortium, approximately 60% of double and triple hit lymphoma patients remained progression free beyond 5 years, and two thirds remained alive. These remarkable data suggest that the majority of double and triple hit lymphomas identified by broad screening of the DLBCL population may be cured with chemoimmunotherapy and should offer encouragement to patients and providers alike. Importantly the Consortium's analysis includes only patients with DLBCL morphology, so excluded double/triple hit patients with Burkitt or Burkitt-like histology who may have an inferior outcome compared to the double hit lymphoma patients in this analysis.
MYC and BCL2 protein expression (so called dual expressor lymphomas) was also analyzed in 1414 cases with available tissue. MYC (≥40%) and BCL2 (≥50%) co-expression was associated with an inferior outcome compared to he general DLBCL population, though better than double/triple hit lymphomas, and notably the majority of dual expressor patients remained free from progression and alive at greater than 2 years of follow up after treatment with R-CHOP-like therapy. On evaluation by cell of origin, patients with GCB-like DLBCL had a slightly more favorable outcome compared to non-GCB, as defined by immunohistochemistry. GCB-like DLBLC more commonly had MYC rearrangements, and exclusively contained the MYC/BCL2 subset of double hit lymphoma, while MYC/BCL6 cases occurred within both cell of origin subgroups.
These robust data from this large systematic analysis address several pressing questions regarding MYC-rearranged DLBCL. First, they tell us that a MYC rearrangement in the absence of a rearrangement of BCL2 and/or BCL6 does not predict an adverse outcome in DLBCL and may be treated as a routine DLBCL with R-CHOP-like therapy. Second, we learn that MYC translocation partner in the setting of a double/triple hit lymphoma matters, with the negative prognosis driven by MYC/Ig translocations rather than MYC rearranged with a non-Ig partner which does not appear to confer negative prognostic influence. Third, while MYC/BCL6 double hit lymphomas are uncommon, they appear to predict similarly inferior outcomes as MYC/BCL2 double hit lymphomas and triple hit lymphomas. And fourth, very importantly, the outcome of double/triple hit DLBCL, though inferior to the entire DLBCL population, appears much better than previously estimated with approximately two thirds of patients achieving long term progression free and overall survival when treated with standard chemoimmunotherapy. It warrants emphasis that this applies to cases morphologically classified as DLBCL, not necessarily to cases with Burkitt-like or blastoid features which were not included in the LLBC study and likely have a less favorable outcome. For this reason, it is essential that pathologists signing out cases as aggressive B-cell lymphoma with translocations of MYC and BCL2 and/or BCL6 also indicate the morphologic subtype as DLBCL versus a higher grade appearance as this information will be essential for clinicians in applying the LLBC findings to prognostication in the clinic.
Finally, this study provides us critically needed guidance in determining which cases warrant evaluation with fluorescence in situ hybridization (FISH) to detect MYC, BCL2 and BCL6 rearrangements. Presently, practice patterns are mixed with some centers testing all cases for MYC, while others test only enriched populations such as GCB-like DLBCL or double expressor DLBCL, and still other centers not routinely evaluating MYC at all in DLBCL. The Consortium data validate that MYC translocations in DLBCL affect a sufficient proportion of the population and confer sufficient prognostic importance as to warrant testing. They also show us that conventional immunohistochemistry for either cell of origin or MYC/BCL2 double expression status are not sufficient to direct FISH testing. Testing only GCB-like DLBCL would indeed identify all cases of MYC/BCL2 double hit lymphomas but would fail to identify a significant proportion of MYC/BCL6 double hit cases. Performing FISH only on cases meeting current immunohistochemical thresholds for MYC and BCL2 double expressor lymphomas would fail to identify more than one quarter of cytogenetically defined double hit lymphomas, which would also be unacceptable. These data therefore support testing all newly diagnosed cases of DLBCL and high-grade B-cell lymphoma with FISH for MYC. A positive FISH assay for MYC should prompt reflexive testing for both BCL2 and BCL6, which would then differentiate cases of single hit cases with MYC translocations alone from the higher risk double and triple hit lymphoma patients.
The fact that the prognostic impact of double and triple hit lymphoma is seen only within the first 2 years from diagnosis underscores the need to optimize upfront therapy in these diseases. The data from the Lunenburg Lymphoma Biomarker Consortium suggest that R-CHOP-like therapy remains an acceptable standard of care in double expressor lymphomas, DLBCL cases with isolated MYC rearrangements, and perhaps even double/triple hit lymphomas with DLBCL morphology, though these cases have increasingly been treated with more intensive regimens such as dose-adjusted EPOCH-R or Burkitt-like regimens based on prior series. In the absence of data clearly supporting one approach versus the other, I would consider either intensive approaches or standard R-CHOP as reasonable considerations in cases of double hit lymphoma with DLBCL morphology and should be individualized to the patient. Ultimately, we would like to overcome biological liabilities with biologically directed therapies, and the US Intergroup is now conducting a randomized clinical trial evaluating chemoimmunotherapy with or without the BCL2 inhibitor venetoclax specifically in double hit and double expressor lymphomas, with the chemoimmunotherapy backbone being dose adjusted EPOCH-R for double hits, and R-CHOP for double expressors. Participation in this important study is encouraged.
This concludes this JCO Podcast. Thank you for listening.