Lunenburg Lymphoma Biomarker Consortium researchers have identified a set of microenvironment-related immunohistochemical and cell-related genetic markers that may help prognosticate follicular lymphoma, according to a recently published study (Haematologica 2017;102(8):1413-1423).
The study investigators found poor outcomes in follicular lymphoma patients to be characterized by a lower number of CD8+ T cells, a smaller CD163+ macrophage area, wild-type EZH2, and a copy number gain of chromosome 18.
The authors wrote that their study may be “the first to comprehensively explore the combined prognostic impact of microenvironment T-cell and macrophage infiltration and tumor genetics of [follicular lymphoma] patients with extremely poor outcome versus those with a prolonged remission.”
Moreover, the gain of chromosome 18, despite its statistically strong prognostic value, had not been previously reported, they stated, adding that whether their findings can be translated to daily clinical practice remains to be seen.
“This study is reasonably well-designed, but we need a bigger cohort of patients to validate these findings,” commented Syed Rizvi, MD, Hematologist/Oncologist and Assistant Professor in the Department of Internal Medicine at UT Southwestern Medical Center in Dallas.
The data provides some areas of interest for further research, but results are not ready to be applied in clinical practice.
Researchers in the Lunenburg Lymphoma Biomarker Consortium performed a validation study evaluating published markers from international trials and registries. They applied an end of spectrum design to 122 follicular lymphoma patients treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) or R-CHOP-like regimens with or without interferon-alpha as maintenance for 2 years. Of these, 49 experienced early failure and 73 had a long follicular lymphoma remission.
Researchers performed immunohistochemical staining for T cells and macrophages on tissue microarrays from biopsies and scored using a validated computer-assisted protocol. They also conducted shallow whole genome and deep targeted sequencing of these samples.
Of the 122 patients, 96 had complete molecular and immunohistochemical data that were analyzed. Investigators found that wild-type EZH2 (P=0.006), a copy number gain of chromosome 18 (P=0.002), and low percentages of CD8+ cells (P=0.011) and CD163+ macrophage areas (P=0.038), a sign of fewer macrophages, were associated with early failure.
They did not observe significant differences in other markers, including PD1+ T follicular helper (TFH) cells and FOXP3+ T regulatory (Treg) cells, “thereby refuting previous claims of their prognostic significance,” the researchers wrote.
Practicalities in the Clinic
Measuring these markers in the clinic may not be ready for “prime time” because of the need for validation and Clinical Laboratory Improvement Amendments (CLIA) certification, said Swami Iyer, MD, Hematologist/Oncologist at the Houston Methodist Cancer Center and Professor of Medicine at Houston Methodist's Institute for Academic Medicine and Weill Cornell Medicine.
Immunohistochemical assays for expression of CD163 and CD8 are available, said Peter Martin, MD, Chief of the Lymphoma Program at Weill Cornell Medicine and NewYork-Presbyterian. However, in this study, researchers performed immunohistochemical testing on tissue microarrays and then used computerized image analysis. Translating these findings to standard pathology labs and accounting for differences in technique and interobserver variability might impact results, he said.
Next-generation sequencing for analysis of copy number and gene mutations is available broadly in research labs, but less so in clinical labs, noted Martin. Copy number could easily be evaluated using fluorescent in situ hybridization assays, which are already broadly available, he added.
Other Cell Populations Still Valuable
Follicular lymphoma studies addressing the prognostic value of microenvironment-related immunohistochemical markers and tumor cell-related genetic markers have produced conflicting results, preventing their use in clinical practice, noted the study authors.
There is “conflicting information in the literature,” about other prognostic markers such as PD1+ TFH cells and FOXP3+ Treg, noted Rizvi.
However, these particular cell populations are still worthy of study, commented Iyer. Researchers have been exploring the presence of immune markers in the microenvironment for some time. Several years ago, an NCI group showed that the presence of such markers can prognosticate follicular lymphoma, he noted (N Engl J Med 2004;351:2159-2169).
Also of importance, cell populations such as PD1+ T TFH cells and FOXP3+ Treg are likely to still have some biological role in follicular lymphoma tumors, “whether or not they have prognostic relevance in the setting of a multivariate analysis,” said Martin. In addition, discounting the results of multiple other studies that have suggested they have prognostic significance based on a single study is premature.
Researchers continue to investigate potential prognostic markers in follicular lymphoma because the current clinical scoring system, Follicular Lymphoma International Prognostic Index (FLIPI), has some limitations. For example, FLIPI doesn't address the underlying biology or the glucose avidity of follicular lymphoma, said Iyer.
While FLIPI is a simple, cheap, reasonably accurate clinical tool, “it does not do a great job of identifying those patients most likely to experience treatment resistance,” said Martin. Modifications of FLIPI that include more biologically based assays might be better. M7-FLIPI, which includes the mutation status of seven genes, is one such example. However, “even these have yet to define how a patient should be treated,” he said, adding that predictive assays are few and far between.
Follicular lymphoma “is a fairly heterogeneous malignancy,” said Rizvi. “It behaves differently in different patients.” Patients with low-grade disease typically do better than those with grade 3B, which may be a different condition altogether. However, some grade 1 follicular lymphoma can be aggressive, while some grade 3A disease can behave in an indolent manner.
Consequently, hematologists/oncologists need tools other than FLIPI to prognosticate, noted Rizvi. While FLIPI is still valuable and has been validated as a prognostic tool for patients taking rituximab, the field of hematology/oncology is moving away from morphological assessment alone and is increasingly incorporating genetic analysis of the disease.
Prognostic Markers & Treatment Implications
Most patients with follicular lymphoma do very well with currently available treatments, noted Martin. “That is not to say that treatments couldn't be made better.” Even if treatments don't cure someone, they could still induce longer remissions, be more convenient, and be associated with fewer side effects.
So far, prognostic markers have not done a great job of impacting treatment selection in follicular lymphoma, said Martin. More biologically based assays may help hematologist/oncologists either select or avoid specific therapies in the future. “Predictive assays may have more relevance when there are more selective, rational treatments,” he said.
The hope is to change patient treatment based on prognostic information, said Rizvi. Patients who have a higher risk of progression may benefit from earlier treatment, although this needs to be further investigated. While upfront treatment does not improve overall survival, it may prolong progression-free survival, he said. As more prognostic information becomes available, clinicians may one day be able to offer therapy that improves overall survival, Rizvi noted.
Validation Studies Needed
In the meantime, researchers need to validate the Lunenburg study using other datasets from follicular lymphoma patients receiving various treatments, said Iyer, adding R-CHOP treatment is not the standard of care for these individuals.
Adequate biological samples also need to be collected, stated Iyer. Biological specimen collection has been extremely poor in the U.S., whereas Europe systematically collects samples on every patient that goes on study, he noted.
Heather Lindsey is a contributing writer.