Rituximab Improves the Outcome of Patients With Grade 3 Follicular Lymphoma Receiving Anthracycline-Based Therapy

High-grade Follicular Lymphomas Exhibit Clinicopathologic, Cytogenetic, and Molecular Diversity Extending Beyond Grades 3A and 3B

Although follicular lymphoma (FL) is usually graded as FL1-2, FL3A, and FL3B, some borderline cases can be observed and led us to investigate the clinicopathologic diversity of grade 3 FL (FL3). Among 2449 FL patients enrolled in Lymphoma Study Association (LYSA) trials, 1921 cases with sufficient material underwent a central pathologic review. The resulting diagnoses comprised 89.6% FL1-2 (n=1723), 7.2% FL3A (n=138), and 0.5% purely follicular FL3B (n=9). The remaining 51 unclassifiable cases (2.7%) exhibited high-grade features but did not meet WHO criteria for either FL3A or FL3B; and were considered as "unconventional" high-grade FL (FL3U). FL3U morphological pattern consisted of nodular proliferation of large cleaved cells or small-sized to medium-sized blast cells. Compared with FL3A, FL3U exhibited higher MUM1 and Ki67 expression, less BCL2 breaks and more BCL6 rearrangements, together with a higher number of cases without any BCL2, BCL6 or MYC rearrangement. FL3U harbored less frequent mutations in BCL2, KMT2D, KMT2B, and CREBBP than FL3A. MYC and BCL2 were less frequently mutated in FL3U than FL3B. Rituximab cyclophosphamide, doxorubicin, vincristine, and prednisone treated FL3U patients had a worse survival than FL1-2 patients with similar follicular lymphoma international prognostic index and treatment. These results suggest that high-grade FLs encompass a heterogeneous spectrum of tumors with variable morphology and genomic alterations, including FL3U cases that do not strictly fit WHO criteria for either FL3A or FL3B, and display a worse outcome than FL1-2. The distinction of FL3U may be useful to allow a better comprehension of high-grade FLs and to design clinical trials.

Relative frequency and clinicopathologic characteristics of MYC-rearranged follicular lymphoma

MYC rearrangement is a relatively rare genetic abnormality in follicular lymphoma (FL). In this study, we evaluated the relative frequency of MYC rearrangement in 522 cases of FL and studied their clinicopathologic, cytogenetic, and molecular characteristics. Fluorescence in situ hybridization studies for MYC (break-apart probe), MYC/IGH, IGH/BCL2, and BCL6 rearrangements were performed on tissue microarrays. Immunohistochemical stains for CD10, BCL2, BCL6, and MYC were performed and scored on MYC-rearranged cases. On 4 FL cases, a custom targeted panel of 356 genes was used for mutation analysis. Ten cases (1.9%) were positive for MYC rearrangement. Histologically, 6 of 10 cases were grade 1-2, and 4 cases were grade 3A. By immunohistochemistry, 9 of 9 tested cases were CD10+, all cases were BCL6+, and 9/10 cases were BCL2+. MYC protein staining was low in all cases tested. IGH/BCL2 rearrangement was detected in 5 of 9 cases, whereas BCL6 rearrangement was detected in 3 of 7 tested cases and 4 of 10 cases showed MYC/IGH rearrangement. The most commonly detected mutations in the MYC-positive cases included HLA-B, TNFRSF14, and KMT2D. MYC and/or B2M abnormalities were detected in 2 cases. In conclusion, MYC rearrangement is uncommon in FL and these cases do not appear to have specific histologic characteristics. Molecular analysis showed abnormalities in genes associated with transformation, namely MYC and B2M. Larger studies are needed to evaluate if MYC-rearrangement in FL has prognostic significance.

The diagnostic and therapeutic challenges of Grade 3B follicular lymphoma

Grade 3B follicular lymphoma (G3B FL) is rare, accounting for only 5-10% of FLs. Not only has it been routinely excluded from clinical trials, but data published on diagnosis, outcomes, choice of therapies and role of imaging are conflicting. With the advent of increasingly diverse treatment options for low-grade (G1-3A) FL, and the molecular subcategorisation of high-grade B-cell lymphomas, characterisation and treatment of G3B FL is ever more important as extrapolation of data becomes more difficult. New data have emerged exploring unique genetic characteristics, specific features on positron emission tomography imaging, choice of therapy, and outcomes of G3B FL in the current era. The present review will summarise and appraise these new data, and offer recommendations based on current evidence.

Prognostic significance of histologic grade and Ki-67 proliferation index in follicular lymphoma

The prognostic value of histologic grading and the Ki-67 proliferation index in follicular lymphoma (FL) is controversial. This study investigated the clinical usefulness of these two factors in Asian FL patients. Four hundred and thirty-three patients diagnosed with FL were retrospectively reviewed with a median follow-up time of 47.0 months (range, 24.0-168.0). The 10-year overall survival (OS) rate and progression-free survival (PFS) rate were 91.0% and 47.1%, respectively. Grade 3B and grade 3B with diffuse large B cell lymphoma (DLBCL) showed a better PFS than grade 1-3A (P < 0.001), and similar findings were noted in patients who received rituximab-containing regimens (P = 0.002). In contrast, no significant differences in terms of OS or PFS were observed between grades 1-2 and 3A. In addition, patients with Ki-67 ≥ 30% had a significantly better PFS than patients with Ki-67 < 30% (P = 0.014), although the difference was eliminated in the multivariate analysis. Both grade and Ki-67 index had no impact on prognosis in patients who did not receive rituximab treatment. In conclusion, grade 3A is closely related to grade 1-2, as reflected by a similar indolent clinical course and a lower PFS rate than grade 3B/3B + DLBCL. In addition, a higher Ki-67 index seems to have a positive effect on PFS in FL patients.

Evaluating Novel PET-CT Functional Parameters TLG and TMTV in Differentiating Low-grade Versus Grade 3A Follicular Lymphoma

BACKGROUND

Follicular lymphoma (FL) grading, low-grade 1-2 (LG) versus grade 3A (3A), informs management. However, accurate grading is challenging owing to disease heterogeneity and inter-reader variability. The [18F]-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) parameter maximum standardized uptake value (SUVmax) has utility in differentiating LG from 3A FL, but the utility of novel parameters total lesion glycolysis (TLG) and total metabolic tumor volume (TMTV) is unknown.

PATIENTS AND METHODS

Retrospective review of diagnostic pre-treatment PET-CTs of patients aged > 18 years with FL grades 1-3A from 2009-2017 was performed. PET-CT parameters SUVmax, TLG, and TMTV values were generated using manual (MW) and semi-automated workflows (SW). Poisson regression and receiver operating characteristic curves were used to compare PET-CT parameters between LG and 3A.

RESULTS

A total of 49 patients with FL were identified: 38 LG and 11 3A. PET-CT parameters were significantly higher in 3A as compared with LG in both workflows. The cutoff values, sensitivities, and specificities were as follows: SUVmax: 10.4, 64%, and 74% in MW and 11.9, 73%, and 76% in SW; TLG: 543, 82%, and 74% in MW and 371, 73%, and 74% in SW; and TMTV: 141, 73%, and 76% in MW and 93, 64%, and 76% in SW. SUVmax had identical cutoff, sensitivity, and specificity across all 3 SWs, whereas TLG and TMTV had considerable variance across all 3 SWs.

CONCLUSIONS

TLG and TMTV are comparable to SUVmax in differentiating LG versus 3A FL. Cutoffs, sensitivities, and specificities varied in MW versus SW. Novel PET-CT parameters serve as reproducible adjuncts but not replacements for biopsy in differentiating grades of FL.

Limited stage grade 3 follicular lymphoma patients can experience favorable outcomes with combined modality therapy

Controversy exists regarding the optimal management of limited stage grade 3 follicular lymphoma (FL3). We assessed the treatment outcomes of 190 consecutive patients with stage I-II FL. Fifty two patients had FL3 disease, in whom the median age was 55 years. At a median follow-up of 65 months, 5-year progression-free survival (PFS) and overall survival (OS) rates were 76.6% and 87.6%, respectively. Patients receiving systemic therapy followed by radiation therapy (RT) had a significantly better PFS (p=.003) than those treated with RT alone, but similar OS (p = .476). Patients treated with RT had 100% local control. Compared to 132 patients with grade 1-2 FL, those with FL3 had similar PFS (p = .493) and OS (p  =  .330). Patients with FL3 can experience favorable outcomes when treated with a combination of systemic therapy and RT, comparable to low grade FL.

Follicular large cleaved cell (centrocytic) lymphoma: an unrecognized variant of follicular lymphoma

The World Health Organization classification of lymphoma recommends the subdivision of follicular lymphoma (FL) into 3 grades (FL1-3) based on the average number of centroblasts per high-power field in the neoplastic follicles, but does not recognize a form of FL characterized by a predominance of large cleaved cells (centrocytes) without enough centroblasts to meet the World Health Organization criteria for FL3. We have classified such cases as follicular large cleaved cell lymphoma (FLC) and, herein, describe the pathologic and clinical features of 72 cases of this entity. The features of FLC include a follicular growth pattern with pale follicles at low magnification and frequent follicular and/or interfollicular fibrosis. Cytologically, the cells are predominantly large cleaved cells with moderately coarse to fine chromatin, absent or inconspicuous nucleoli, and small to moderate amounts of pale cytoplasm. The mean nuclear diameter of the large cleaved cells was 10.1μ, approximately twice that of small lymphocytes and similar to centroblasts. The t(14;18) was present in 83% of the cases, and a high proportion expressed BCL2 (84%), BCL6 (100%), and CD10 (88%) and had high Ki67 proliferation (81%). The clinical features of patients with FLC were similar to those with other types of FL, and survival was excellent with anthracycline-based chemotherapy plus rituximab. FLC is a variant of follicular lymphoma which should be recognized in future lymphoma classifications because the diagnosis of FLC may be important for the selection of therapy.