Prognostic model for high-tumor-burden follicular lymphoma integrating baseline and end-induction PET: a LYSA/FIL study

Baseline 18F-FDG PET/CT may contribute to the determination of initial treatment strategy for newly diagnosed follicular lymphoma

BACKGROUND

"Watch-and-wait" approach is an important management option in asymptomatic follicular lymphoma (FL) patients with low tumor burden. Since most FL lesions are FDG-avid, we wonder if 18F-FDG PET/CT at baseline can help to better choose the patients who can benefit from early chemotherapy. This study aimed to investigate the prognostic value of baseline 18F-FDG PET/CT in newly diagnosed FL patients treated with either watch-and-wait approach or chemotherapy.

RESULTS

Patients received chemotherapy as initial treatment had higher Ann Arbor stage, higher incidence of extranodal involvement and bulky disease, more involved lymph nodes larger than 3 cm, and higher SUVmax, MTV, and TLG than those managed with watch-and-wait approach (p < 0.05). The median PFS and TTNT in patients received chemotherapy and under watch-and-wait did not show significant difference, however patients with MTV<111.66 mL or TLG<141.50 SUVbw*mL had significantly longer PFS and TTNT than those patients with MTV≥111.66 mL or TLG≥141.50 SUVbw*mL (p < 0.05). Further analysis revealed that for patients with TLG≥141.50 SUVbw*mL or MTV≥111.66 mL, those who received chemotherapy as initial treatment had a significantly longer PFS and TTNT than those managed with initial watch-and-wait approach (p < 0.05). However, for patients with MTV<111.66 mL or TLG<141.50 SUVbw*mL in baseline PET/CT, there was no significant difference in PFS or TTNT between patients who received chemotherapy and those under watch-and-wait.

CONCLUSION

Baseline 18F-FDG PET/CT may provide prognostic value and help to improve the decision-making of initial treatment plans for newly diagnosed FL patients.

Long-Term Follow-Up of Patients With Follicular Lymphoma Using Next Generation Sequencing to Detect Minimal Residual Disease

BACKGROUND

Follicular lymphoma (FL) is a highly treatable, indolent non-Hodgkin lymphoma. Although FL is considered incurable, a patient without progression of disease by 24 months after treatment is predicted to have a survival consistent with persons without lymphoma. Using a sensitive assessment of minimal residual disease (MRD), we tested the hypothesis that MRD monitoring can predict long term remissions.

METHODS

Unselected patients who were in a clinical remission for at least 24 months after their last treatment were enrolled and monitored prospectively for MRD detectability using a sensitive next-generation sequencing assay (clonoSEQ, Adaptive Biotechnologies, Seattle, WA).

RESULTS

Forty-seven consecutive patients were monitored. We evaluated the MRD thresholds 10-4, 10-5, and 10-6 for the ability to predict long-term remissions in this cohort and determined that undetectable disease at 10-6 was the best predictor with a specificity and negative predictive value (NPV) of 70% and 100%, respectively. While 3 patients exhibited clinical disease progression during the course of the study, none of the 31 patients with persistent MRD undetectability at 10-6 experienced relapse.

CONCLUSIONS

A significant proportion (31/47; 66.0%) of FL patients in clinical remission after ≥24 months following last therapy were undetectable at 10-6 by a sensitive assay of MRD. The threshold of sensitivity was 100%, specificity 70%, with a PPV of 19%, but a NPV of 100%. Although longer follow-up is needed for confirmation, many of these patients may continue to have durable complete remissions.

Prognostic value of the combination of volume, massiveness and fragmentation parameters measured on baseline FDG pet in high-burden follicular lymphoma

The prognostic value of radiomic quantitative features measured on pre-treatment 18F-FDG PET/CT was investigated in patients with follicular lymphoma (FL). We conducted a retrospective study of 126 FL patients (grade 1-3a) diagnosed between 2006 and 2020. A dozen of PET/CT-derived features were extracted via a software (Oncometer3D) from baseline 18F-FDG PET/CT images. The receiver operating characteristic (ROC) curve, Kaplan-Meier method and Cox analysis were used to assess the prognostic factors for progression of disease within 24 months (POD24) and progression-free survival at 24 months. Four different clusters were identified among the twelve PET parameters analyzed: activity, tumor burden, fragmentation-massiveness and dispersion. On ROC analyses, TMTV, the total metabolic tumor volume, had the highest AUC (0.734) followed by medPCD, the median distance between the centroid of the tumors and their periphery (AUC: 0.733). Patients with high TMTV (HR = 4.341; p < 0.001), high Tumor Volume Surface Ratio (TVSR) (HR = 3.204; p < 0.003) and high medPCD (HR = 4.507; p < 0.001) had significantly worse prognosis in both Kaplan-Meier and Cox univariate analyses. Furthermore, a synergistic effect was observed in Kaplan-Meier and Cox analyses combining these three PET/CT-derived parameters (HR = 12.562; p < 0.001). Having two or three high parameters among TMTV, TVSR and medPCD was able to predict POD24 status with a specificity of 68% and a sensitivity of 75%. TMTV, TVSR and baseline medPCD are strong prognostic factors in FL and their combination better predicts disease prognosis.

Metabolic tumor volume predicts outcome in patients with advanced stage follicular lymphoma from the RELEVANCE trial

BACKGROUND

We investigated the prognostic value of baseline positron emission tomography (PET) parameters for patients with treatment-naïve follicular lymphoma (FL) in the phase III RELEVANCE trial, comparing the immunomodulatory combination of lenalidomide and rituximab (R2) versus R-chemotherapy (R-chemo), with both regimens followed by R maintenance therapy.

PATIENTS AND METHODS

Baseline characteristics of the entire PET-evaluable population (n = 406/1032) were well balanced between treatment arms. The maximal standard uptake value (SUVmax) and the standardized maximal distance between tow lesions (SDmax) were extracted, the standardized distance between two lesions the furthest apart, were extracted. The total metabolic tumor volume (TMTV) was computed using the 41% SUVmax method.

RESULTS

With a median follow-up of 6.5 years, the 6-year progression-free survival (PFS) was 57.8%, the median TMTV was 284 cm3, SUVmax was 11.3 and SDmax was 0.32 m-1, with no significant difference between arms. High TMTV (>510 cm3) and FLIPI were associated with an inferior PFS (P = 0.013 and P = 0.006, respectively), whereas SUVmax and SDmax were not (P = 0.08 and P = 0.12, respectively). In multivariable analysis, follicular lymphoma international prognostic index (FLIPI) and TMTV remained significantly associated with PFS (P = 0.0119 and P = 0.0379, respectively). These two adverse factors combined stratified the overall population into three risk groups: patients with no risk factors (40%), with one factor (44%), or with both (16%), with a 6-year PFS of 67.7%, 54.5%, and 41.0%, respectively. No significant interaction between treatment arms and TMTV or FLIPI (P = 0.31 or P = 0.59, respectively) was observed. The high-risk group (high TMTV and FLIPI 3-5) had a similar PFS in both arms (P = 0.45) with a median PFS of 68.4% in the R-chemo arm versus 71.4% in the R2 arm.

CONCLUSIONS

Baseline TMTV is predictive of PFS, independently of FLIPI, in patients with advanced FL even in the context of antibody maintenance.

Thinking "outside the germinal center": Re-educating T cells to combat follicular lymphoma

There have been significant advancements in the management of follicular lymphoma (FL), the most common indolent lymphoma. These include immunomodulatory agents such as lenalidomide, epigenetic modifiers (tazemetostat), and phosphoinotiside-3 kinase inhibitors (copanlisib). The focus of this review is T cell-engager therapies, namely chimeric antigen receptor (CAR) T-cell therapy and bispecific antibodies, have recently transformed the treatment landscape of FL. Two CAR T cell products, axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel), and one bispecific antibody, mosunetuzumab, recently received FDA approvals in FL. Several other new immune effector drugs are being evaluated and will expand the treatment armamentarium. This review focuses on CAR T-cell and bispecific antibody therapies, details their safety and efficacy and considers their evolving role in the current treatment landscape of FL.

Quantitative PET-based biomarkers in lymphoma: getting ready for primetime

The use of functional quantitative biomarkers extracted from routine PET-CT scans to characterize clinical responses in patients with lymphoma is gaining increased attention, and these biomarkers can outperform established clinical risk factors. Total metabolic tumour volume enables individualized estimation of survival outcomes in patients with lymphoma and has shown the potential to predict response to therapy suitable for  risk-adapted treatment approaches in clinical trials. The deployment of machine learning tools in molecular imaging research can assist in recognizing complex patterns and, with image classification, in tumour identification and segmentation of data from PET-CT scans. Initial studies using fully automated approaches to calculate metabolic tumour volume and other PET-based biomarkers have demonstrated appropriate correlation with calculations from experts, warranting further testing in large-scale studies. The extraction of computer-based quantitative tumour characterization through radiomics can provide a comprehensive view of phenotypic heterogeneity that better captures the molecular and functional features of the disease. Additionally, radiomics can be integrated with genomic data to provide more accurate prognostic information. Further improvements in PET-based biomarkers are imminent, although their incorporation into clinical decision-making currently has methodological shortcomings that need to be addressed with confirmatory prospective validation in selected patient populations. In this Review, we discuss the current knowledge, challenges and opportunities in the integration of quantitative PET-based biomarkers in clinical trials and the routine management of patients with lymphoma.

Risk Factors of Progression in Low-tumor Burden Follicular Lymphoma Initially Managed by Watch and Wait in the Era of PET and Rituximab

Patients (pts) with asymptomatic low-burden follicular lymphoma (FL) are usually observed at diagnosis. Time to lymphoma treatment (TLT) initiation can however be very heterogeneous and risk factors of progression are poorly studied. Our study evaluated 201 pts with grade 1-3a low-tumor burden FL diagnosed in four French centers between 2010 and 2020 and managed by a watch and wait strategy in real-life settings. After a median follow-up of 4.8 years, the median TLT was 4.2 years (95% confidence interval, 3.1-5.5). On multivariate analysis, elevated lactate dehydrogenase (hazard ratio [HR] = 2.2; P = 0.02), more than 4 nodal areas involved (HR = 1.7; P = 0.02) and more than 1 extranodal involvement (HR = 2.7; P = 0.01) were identified as independent predictors of TLT. The median TLT was 5.8 years for pts with no risk factor, 2.4 years for 1 risk factor, and 1.3 years for >1 risk factors (P < 0.01). In a subanalysis of 75 pts staged with positron emission tomography-computed tomography (PET-CT), total metabolic tumor volume (TMTV) ≥14 cm³ and standardized Dmax (reflecting tumor dissemination) >0.32 m^-1 were also associated with shorter TLT (HR = 3.4; P = 0.004 and HR = 2.4; P = 0.007, respectively). In multivariate models combining PET-CT parameters and clinical variables, TMTV remained independent predictor of shorter TLT. These simple parameters could help to identify FL patients initially observed at higher risk of early progression. The role of PET-CT (extranodal sites and PET metrics) in low-burden FL appears promising and warrants further assessment in large cohorts.

PET/CT in Non-Hodgkin Lymphoma: An Update

Non-Hodgkin lymphomas represents a heterogeneous group of lymphoproliferative disorders characterized by different clinical courses, varying from indolent to highly aggressive. ¹⁸F-FDG-PET/CT is the current state-of-the-art diagnostic imaging, for the staging, restaging and evaluation of response to treatment in lymphomas with avidity for ¹⁸F-FDG, despite it is not routinely recommended for surveillance. PET-based response criteria (using five-point Deauville Score) are nowadays uniformly applied in FDG-avid lymphomas. In this review, a comprehensive overview of the role of ¹⁸F-FDG-PET in Non-Hodgkin lymphomas is provided, at each relevant point of patient management, particularly focusing on recent advances on diffuse large B-cell lymphoma and follicular lymphoma, with brief updates also on other histotypes (such as marginal zone, mantle cell, primary mediastinal- B cell lymphoma and T cell lymphoma). PET-derived semiquantitative factors useful for patient stratification and prognostication and emerging radiomics research are also presented.

Managing Follicular Lymphoma in the Elderly Population

Follicular lymphoma (FL) is one of the most commonly diagnosed types of indolent non-Hodgkin lymphoma (NHL). The median age of diagnosis for FL is 65 years old. Although the median life expectancy after diagnosis is approximately 10 years, the incurable disease has a high risk of transformation. This case report focuses on an 80-year-old patient diagnosed with low-grade follicular lymphoma which subsequently transformed leading to the patient's eventual demise as the patient took on the palliative intent. This case report aims to highlight the importance of clinical markers or prognostic factors to identify patients, specifically the elderly population who are at risk of transformation to aggressive forms when their FL remains at stage I-II phases. Currently, elderly patients with FL tend to be quickly dismissed with curative intent with chemotherapy, given their age and comorbidities, despite forming the majority of the population with follicular lymphoma. Age more than 60 years old has been shown to be one of the most powerful yet poor prognostic features in follicular lymphoma international prognostic index (FLIPI)-the main scoring system used for FL. Hence, further studies are required to look into the tailoring treatment for elderly patients with follicular lymphoma after risk stratifying them with appropriate clinical and prognostic markers.

Monitoring of Circulating Tumor DNA Predicts Response to Treatment and Early Progression in Follicular Lymphoma: Results of a Prospective Pilot Study

PURPOSE

Follicular lymphoma (FL) is the most frequent indolent non-Hodgkin lymphoma. Around 20% of patients suffer early disease progression within 24 months (POD24) of diagnosis. This study examined the significance of circulating tumor DNA (ctDNA) in predicting response to therapy and POD24 in patients with FL.

EXPERIMENTAL DESIGN

We collected 100 plasma samples, before and during the treatment, from 36 patients with FL prospectively enrolled in 8 Spanish hospitals. They were treated with a chemotherapy-rituximab regimen and followed up for a median of 3.43 years. We performed targeted deep sequencing in cell-free DNA (cfDNA) and tumor genomic DNA from 31 diagnostic biopsy samples.

RESULTS

Of the alterations detected in the diagnostic tissue samples, 73% (300/411) were also identified in basal cfDNA. The mean numbers of alterations per basal cfDNA sample in patients who suffered progression of disease within 24 months (POD24-pos) or did not achieve complete response (non-CR) were significantly higher than in POD24-neg or CR patients (unpaired samples t test, P = 0.0001 and 0.001, respectively). Pretreatment ctDNA levels, as haploid genome equivalents per milliliter of plasma, were higher in patients without CR (P = 0.02) and in POD24-pos patients compared with POD24-neg patients (P < 0.001). Dynamic analysis showed that ctDNA levels decreased dramatically after treatment, although the reduction was more significant in patients with CR and POD24-neg patients.

CONCLUSIONS

Basal ctDNA levels are associated with the risk of early progression and response to treatment in FL. cfDNA monitoring and genotyping during treatment and follow-up predict response to treatment and early progression.

Prospective Evaluation of Different Methods for Volumetric Analysis on [18F]FDG PET/CT in Pediatric Hodgkin Lymphoma

Rationale: Therapy response evaluation by 18F-fluorodeoxyglucose PET/CT (FDG PET) has become a powerful tool for the discrimination of responders from non-responders in pediatric Hodgkin lymphoma (HL). Recently, volumetric analyses have been regarded as a valuable tool for disease prognostication and biological characterization in cancer. Given the multitude of methods available for volumetric analysis in HL, the AIEOP Hodgkin Lymphoma Study Group has designed a prospective analysis of the Italian cohort enrolled in the EuroNet-PHL-C2 trial. Methods: Primarily, the study aimed to compare the different segmentation techniques used for volumetric assessment in HL patients at baseline (PET1) and during therapy: early (PET2) and late assessment (PET3). Overall, 50 patients and 150 scans were investigated for the current analysis. A dedicated software was used to semi-automatically delineate contours of the lesions by using different threshold methods. More specifically, four methods were applied: (1) fixed 41% threshold of the maximum standardized uptake value (SUVmax) within the respective lymphoma site (V41%), (2) fixed absolute SUV threshold of 2.5 (V2.5); (3) SUVmax(lesion)/SUVmean liver >1.5 (Vliver); (4) adaptive method (AM). All parameters obtained from the different methods were analyzed with respect to response. Results: Among the different methods investigated, the strongest correlation was observed between AM and Vliver (rho > 0.9; p < 0.001 for SUVmean, MTV and TLG at all scan timing), along with V2.5 and AM or Vliver (rho 0.98, p < 0.001 for TLG at baseline; rho > 0.9; p < 0.001 for SUVmean, MTV and TLG at PET2 and PET3, respectively). To determine the best segmentation method, we applied logistic regression and correlated different results with Deauville scores at late evaluation. Logistic regression demonstrated that MTV (metabolic tumor volume) and TLG (total lesion glycolysis) computation according to V2.5 and Vliver significantly correlated to response to treatment (p = 0.01 and 0.04 for MTV and 0.03 and 0.04 for TLG, respectively). SUVmean also resulted in significant correlation as absolute value or variation. Conclusions: The best correlation for volumetric analysis was documented for AM and Vliver, followed by V2.5. The volumetric analyses obtained from V2.5 and Vliver significantly correlated to response to therapy, proving to be preferred thresholds in our pediatric HL cohort.

Risk factors for POD24 in patients with previously untreated follicular lymphoma: a systematic review and meta-analysis

Progression of disease within 24 months (POD24) is strongly associated with a poor outcome in patients with follicular lymphoma (FL). Our study aimed to identify the potential risk factors for POD24 in patients with FL. Medline, EMBASE and the Cochrane Library were systematically searched from the earliest record to September 2020. Studies investigating the prognostic factors for POD24 in patients with newly diagnosed grade 1-3a FL were included. Among 10,014 pieces of literature, a total of 90 studies investigating 82 risk factors were included for qualitative analysis. Meta-analyses were performed in 31 studies with 11 factors. Results showed that elevated sIL-2R, β2m and LDH, total metabolic tumour volume > 510 cm³, vitamin D < 20 ng/mL, grade 3a and lymphoma-associated macrophages/high-power field ≥ 15 were significantly associated with an increased risk of POD24. No significant association was found between POD24 and the ALC/AMC ratio, sex, T effector signature or EZH2 genetic alteration. Additionally, minimal residual disease, Ki-67, PD-1 and TP53 were analysed narratively. Overall, this is the first study that comprehensively analysed the prognostic factors associated with POD24 in FL patients. We have confirmed the significance value of several common prognostic factors as well as others not commonly included in clinical study, helping to construct an integrated and more efficient model.

Prediction of prognosis and pathologic grade in follicular lymphoma using 18F-FDG PET/CT

Purpose

We investigated the utility of a new baseline PET parameter expressing lesion dissemination and metabolic parameters for predicting progression-free survival (PFS) and pathologic grade in follicular lymphoma (FL).

Methods

The baseline ¹⁸F-FDG PET/CT images of 126 patients with grade 1–3A FL were retrospectively analyzed. A novel PET/CT parameter characterizing lesion dissemination, the distance between two lesions that were furthest apart (D_max), was calculated. The total metabolic tumor volume and total lesion glycolysis (TLG) were computed by using 41% of the maximum standardized uptake value (SUV_max) thresholding method.

Results

The 5-year PFS rate was 51.9% for all patients. In the multivariate analysis, high D_max [P = 0.046; hazard ratio (HR) = 2.877], high TLG (P = 0.004; HR = 3.612), and elevated serum lactate dehydrogenase (P = 0.041; HR = 2.287) were independent predictors of PFS. A scoring system for prognostic stratification was established based on these three adverse factors, and the patients were classified into three risk categories: low risk (zero to one factor, n = 75), intermediate risk (two adverse factors, n = 29), and high risk (three adverse factors, n = 22). Patients in the high-risk group had a shorter 3-year PFS (21.7%) than those in the low- and intermediate-risk groups (90.6 and 44.6%, respectively) (P < 0.001). The C-index of our scoring system for PFS (0.785) was superior to the predictive capability of the Follicular Lymphoma International Prognostic Index (FLIPI), FLIPI2, and PRIMA-Prognostic Index (C-index: 0.628–0.701). The receiver operating characteristic curves and decision curve analysis demonstrated that the scoring system had better differentiation and clinical utility than these existing indices. In addition, the median SUV_max was significantly higher in grade 3A (36 cases) than in grades 1 and 2 FL (90 cases) (median: 13.63 vs. 11.45, P = 0.013), but a substantial overlap existed (range: 2.25–39.62 vs. 3.17–39.80).

Conclusion

TLG and D_max represent two complementary aspects of the disease, capturing the tumor burden and lesion dissemination. TLG and D_max are promising metrics for identifying patients at a high risk of progression or relapse. Additionally, SUV_max seems to have some value for distinguishing grade 3A from low-grade FL but cannot substitute for biopsy.

High baseline total lesion glycolysis predicts early progression of disease within 24 months in patients with high-tumor-burden follicular lymphoma

Despite the introduction of rituximab-containing regimens, approximately 20% of patients with follicular lymphoma (FL) still experience progression of disease within 24 months (POD24) and have poor overall survival. Therefore, a more accurate risk assessment tool is required. We investigated the predictive value of two new volume-based parameters determined from baseline 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT), baseline total metabolic tumor volume (TMTV) and total lesion glycolysis (TLG), in 45 patients with high-tumor-burden FL who underwent baseline PET/CT. We observed that high TMTV, high TLG, and poor initial treatment response (less than complete [metabolic] response [non-CR/CMR] at the end of induction therapy) independently predicted poor PFS. Notably, POD24-positive patients were more common in the high-TLG group than in the high-TMTV group, which suggests that TLG is a stronger predictor of outcomes than TMTV. Combining baseline TLG and initial treatment response showed that patients with both high TLG and non-CR/CMR experienced significantly poorer outcomes, with a 2 year PFS of 0% (hazard ratio 60.39, P = 0.000002). This combination had 56% sensitivity and 100% specificity for detecting patients who would experience POD24. Baseline TLG and initial treatment response can precisely identify patients at high risk of POD24.

Predicting time to treatment in follicular lymphoma on watchful waiting using baseline metabolic tumour burden

PURPOSE

Asymptomatic patients with follicular lymphoma (FL) and a low tumour burden can be followed without initial therapy, a strategy called watchful waiting (WW). Prediction of the time to treatment (TTT) is still a challenge. We investigated the prognostic value of baseline total metabolic tumour volume (TMTV) and whole-body total lesion glycolysis (WB-TLG) to predict TTT in patients with FL on WW.

METHODS

We conducted a retrospective study of 54 patients with FL (grade 1-3a) diagnosed between June 2013 and December 2019, staged with FDG PET/CT, and managed on WW. Median age was 62 years (range 34-85), stage was advanced (III-IV) in 57%, and FLIPI score was intermediate to high (≥ 2) in 52% of the patients.

RESULTS

The median TMTV and WB-TLG were 7.1 and 43.3, respectively. With a median follow-up of 59 months, 41% of patients started immuno-chemotherapy. The optimal cut-points to identify patients with TTT within 24 months were 14 for TMTV (AUC 0.70; 95% CI 51-88) and 64 for WB-TLG (AUC 0.71; 95% CI 52-89) (p < 0.005). The probability of not having started treatment within 24 months was 87% for TMTV < 14 and 53% for TMTV ≥ 14 (p < 0.005). TMTV was independent of the FLIPI score for TTT prediction. Patients with both FLIPI ≥ 2 and TMTV ≥ 14 had only an 18% probability of not having started treatment at 36 months, while this probability was 75% in patients with TMTV < 14.

CONCLUSION

Metabolic tumour volume parameters may add information to clinical scores to better predict TTT and better stratify patients for interventional studies.

Clinical application of [18F]FDG PET/CT in follicular lymphoma

The objective of the present paper was to review the clinical application of [¹⁸F]FDG PET/CT in follicular lymphoma (FL). Once it was clear that, despite it is characterized as indolent, this type of lymphoma usually shows a high [¹⁸F]FDG avidity, PET/CT became more important and it's now considered the standard technique in staging, re-staging and response evaluation. Many studies have shown its impact on the management of patients (as it can change the stage in a significant proportion of cases and lead to treatment modifications), its superiority over CT (mainly because it's able to distinguish fibrosis in residual masses from viable tumor) and its prognostic value. The latter was initially associated only to the degree of metabolic response, which has proved to be a strong and independent predictive factor in terms of disease-free survival (DFS) and overall survival (OS). Thus, a negative PET/CT scan could be considered a guarantee in high-tumor-burden follicular lymphoma patients. However, semiquantitative parameters such as metabolic tumor volume or total lesion glycolysis, may also provide useful information and help us to identify patients with poor prognosis, guiding a risk-adjusted management and follow-up.

Validation of POD24 as a robust early clinical end point of poor survival in FL from 5225 patients on 13 clinical trials

Observational studies and stand-alone trials indicate that patients with follicular lymphoma (FL) who experience disease progression within 24 months of front-line chemoimmunotherapy (POD24), have poor outcomes. We performed a pooled analysis of 13 randomized clinical trials of patients with FL in the pre- and postrituximab eras to identify clinical factors that predict POD24. Logistic regression models evaluated the association between clinical factors and POD24. Cox regression evaluated the association between POD24 as a time-dependent factor and subsequent overall survival (OS). A landmark analysis evaluated the association of POD24 with OS for the subset of patients who were alive at 24 months after trial registration. Patients without progression at 24 months at baseline had favorable performance status (PS), limited-stage (I/II) disease, low-risk FL International Prognostic Index (FLIPI) score, normal baseline hemoglobin, and normal baseline β2 microglobulin (B2M) level. In a multivariable logistic regression model, male sex (odds ratio [OR], 1.30), PS ≥2 (OR, 1.63), B2M (≥3 mg/L; OR, 1.43), and high-risk FLIPI score (3-5; OR, 3.14) were associated with increased risk of progression before 24 months. In the time-dependent Cox model and the 24-month landmark analysis, POD24 was associated with poor subsequent OS (hazard ratio, 4.85 and 3.06, respectively). This is the largest pooled analysis of clinical trials data validating POD24 as a robust indicator of poor FL survival and identified clinical predictors of early death and progression that can aid in building comprehensive prognostic models incorporating clinical and molecular predictors of POD24.

Cerebellum/liver index in pretherapeutic 18F-FDG PET/CT as a predictive marker of progression-free survival in follicular lymphoma treated by immunochemotherapy and rituximab maintenance

The purpose of this study was to investigate the value of the "cerebellum/ liver index for prognosis" (CLIP) as a new prognostic marker in pretherapeutic 18F-Fluorodeoxyglucose positron emission tomography (18F-FDG PET) in patients with follicular lymphoma treated by immunochemotherapy and rituximab maintenance, focusing on progression-free survival (PFS).Clinicobiological and imaging data from patients with follicular lymphoma between March 2010 and September 2015 were retrospectively collected and 5-year PFS was determined. The conventional PET parameters (maximum standardized uptake value and total metabolic tumor volume) and the CLIP, corresponding to the ratio of the cerebellum maximum standardized uptake value over the liver SUVmean, were extracted from the pretherapeutic 18F-FDG PET.Forty-six patients were included. Eighteen patients (39%) progressed within the 5 years after treatment initiation. Five-year PFS was 78.6% when CLIP was >4.0 and 42.0% when CLIP was <4.0 (P = .04). CLIP was a significant predictor of PFS on univariate analysis (hazard ratio 3.1, P = .049) and was near-significant on multivariate analysis (hazard ratio 2.8, P = .07) with ECOG PS as a cofactor.The CLIP derived from pretherapeutic 18F-FDG PET seems to be an interesting predictive marker of PFS in follicular lymphoma treated by immunochemotherapy and rituximab maintenance. These results should be evaluated prospectively in a larger cohort.

Pre-treatment total metabolic tumour volumes in lymphoma: Does quantity matter?

Positron emission tomography/computed tomography (PET/CT) is used for the staging of lymphomas. Clinical information, such as Ann Arbor stage and number of involved sites, is derived from baseline staging and correlates with tumour volume. With modern imaging software, exact measures of total metabolic tumour volumes (tMTV) can be determined, in a semi- or fully-automated manner. Several technical factors, such as tumour segmentation and PET/CT technology influence tMTV and there is no consensus on a standardized uptake value (SUV) thresholding method, or how to include the volumes in the bone marrow and spleen. In diffuse large B-cell lymphoma, follicular lymphoma, peripheral T-cell lymphoma, and Hodgkin lymphoma, tMTV has been shown to predict progression-free survival and/or overall survival, after adjustments for clinical risk scores. However, most studies have used receiver operating curves to determine the optimal cut-off for tMTV and many studies did not include a training-validation approach, which led to the risk of overestimation of the independent prognostic value of tMTV. The identified cut-off values are heterogeneous, even when the same SUV thresholding method is used. Future studies should focus on testing tMTV in homogeneously-treated cohorts and seek to validate identified cut-off values externally so that a prognostic value can be documented, over and above currently used clinical surrogates for tumour volume.

Follicular lymphoma: is there an optimal way to define risk?

Follicular lymphoma (FL) has a long natural history and typically indolent behavior. In the present era, there are a plethora of prognostic factors combining clinical, biological, and genetic data to determine patient prognosis and help develop treatment strategies over the course of a patient's lifetime. The rapid pace of tumor-specific and clinical advances in FL has created a challenge in the prioritization and implementation of these factors into clinical practice. Developing a comprehensive understanding of existing prognostic markers in FL will help select optimal ways of utilization in the clinical setting and investigate opportunities to define and intervene upon risk at FL diagnosis and disease recurrence.

Current Role of Functional Imaging in the Management of Lymphoma

PURPOSE OF REVIEW

Functional imaging with 18FDG-PET-CT has transformed the staging and response assessment of patients with Hodgkin (HL) and non-Hodgkin lymphoma (NHL). Herein, we review the current role and future directions for functional imaging in the management of patients with lymphoma.

RECENT FINDINGS

Because of its increased sensitivity, PET-CT is the preferred modality for staging of FDG-avid lymphomas. It appears to have a role for interim assessment in patients with HL with adaptive strategies that reduce toxicity in lower risk patients and increase efficacy in those at high risk. Such a role has yet to be demonstrated in other histologies. FDG-PET-CT is also the gold standard for response assessment posttreatment. Newer uses include assessment of total metabolic tumor volume and radiomics in pretreatment prognosis. Whereas PET-CT is more sensitive than other current modalities for staging and response assessment, the future of PET-CT will be in conjunction with other modalities, notably assessment of minimal residual disease and microenvironmental markers to develop risk adaptive strategies to improve the outcome of patients with lymphoma.

The optimal use of PET/CT in the management of lymphoma patients

¹⁸F-fluoro-deoxyglucose positron emission tomography (PET)/computed tomography (CT) scans play an important role in the management of lymphoma patients. They are critical to accurately stage disease and assess its response to therapy. In addition, PET/CT scans enable precise target delineation for radiation therapy planning. In this review, we describe the use of PET/CT scans in lymphoma, with a focus on their role in staging disease, assessing response to therapy, predicting prognosis, and planning RT.

Prognostic value of baseline metabolic tumor volume in children and adolescents with intermediate-risk Hodgkin lymphoma treated with chemo-radiation therapy: FDG-PET parameter analysis in a subgroup from COG AHOD0031

BACKGROUND

Positron emission tomography (PET)-based measures of baseline total-body tumor burden may improve risk stratification in intermediate-risk Hodgkin lymphoma (HL).

MATERIALS AND METHODS

Evaluable patients were identified from a cohort treated homogeneously with the same combined modality regimen on the Children's Oncology Group AHOD0031 study. Eligible patients had high-quality baseline PET scans. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were each measured based on 15 thresholds for every patient. Univariate and multivariable Cox regression and Kaplan-Meier survival analyses assessed for an association of MTV and TLG with event-free survival (EFS).

RESULTS

From the AHOD0031 cohort (n = 1712), 86 patients were identified who (i) were treated with four cycles of doxorubicin, bleomycin, vincristine, etoposide, prednisone, cyclophosphamide (ABVE-PC) chemotherapy followed by involved field radiotherapy, and (ii) had a baseline PET scan that was amenable to quantitative analysis. Based on univariate Cox regression analysis, six PET-derived parameters were significantly associated with EFS. For each of these, Kaplan-Meier analyses and the log-rank test were used to compare patients with highest tumor burden (i.e., highest 15%) to the remainder of the cohort. EFS was significantly associated with all six PET parameters (all p < .029). In a multivariable model controlling for important covariates including disease bulk and response to chemotherapy, MTV_2BP was significantly associated with EFS (p = .012).

CONCLUSION

Multiple baseline PET-derived volumetric parameters were associated with EFS. MTV_2BP was highly associated with EFS when controlling for disease bulk and response to chemotherapy. Incorporation of baseline MTV into risk-based treatment algorithms may improve outcomes in intermediate-risk HL.

Follicular Lymphoma: Refining Prognostic Models and Impact of Pod-24 in Clinical Outcomes

Follicular lymphoma (FL) is the most common indolent lymphoma, accounting for 20%-25% of all non-Hodgkin's lymphomas (NHLs). It is a malignancy with variable biologic presentation and heterogeneous clinical outcomes. Several models incorporating clinical laboratory variables and molecular biomarkers are able to predict its prognosis, allowing to stratify patients into different risk groups. However, these prognostic scores should not be used to indicate first-line treatment or risk-adapted therapeutic recommendations. Over the past 5 years, progression of disease within 24 months (POD-24) of first-line chemo-immunotherapy has emerged as a robust adverse prognostic factor, capable of assessing overall survival and identifying high-risk patients with indication for more aggressive therapeutic approaches, such as consolidation based in autologous stem cell transplantation. It should be reinforced that POD-24 is not a baseline measurement, it is based on a post-treatment strategy, and is usually applied to patients with a high tumor burden. The identification of newly diagnosed patients at high risk for disease progression, particularly those with low tumor volume is still a challenge in the context of FL. Therefore, the primary purpose of this review is to provide an overview of the main prognostic models validated to date for FL. Moreover, using these scores, which incorporate clinical and genetic variables, we aim to identify individuals with newly diagnosed FL, advanced disease, and low tumor burden with a high probability of progression or relapse within 24 months of first treatment. Thus, a decision regarding risk-adapted induction therapy could be better stablished for these subset of patients.

Significance of initial, interim and end-of-therapy 18F-FDG PET/CT for predicting transformation risk in follicular lymphoma

Background

Histological transformation (HT) of follicular lymphoma to a more aggressive lymphoma is a serious event affecting patients’ outcomes. To date, no strong clinical HT predictors present at diagnosis have yet been identified. The fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) is highlighted as a non-invasive diagnostic tool for the detection of HT, but its ability to predict HT at early stage of disease has not been clear. Therefore, this study investigated the predictive values of the pre-transformation standardized uptake value (SUV_max) for the risk of transformation in FL.

Methods

This retrospective study involved 219 patients with FL between June 2008 and October 2019 who had undergone ¹⁸F-FDG PET/CT scan. One hundred and thirty-two, 64, and 78 patients underwent PET at baseline (PET_baseline), interim (PET_interim) and end-of-induction therapy (PET_end), respectively. Qualitative assessment was performed using the 5-point Deauville scale. Statistical analysis was done using Cox regression models, receiver operating characteristic (ROC) analysis, and Kaplan–Meir survival curves.

Results

Of the 219 patients included, 128 had low-grade FL (grade 1–2) and 91 had high-grade FL (grade 3a). HT eventually occurred in 30 patients. The median time to HT was 13.6 months. Among clinical indicators, advance pathological grade was shown as the most significant predictor of HT (HR = 4.561, 95% CI 1.604–12.965). We further assessed the relationship between PET and HT risk in FL. Univariate Cox regression determined that SUV_baseline and SUV_end were significant predictors for HT, while neither SUV_interim nor qualitative assessment of Deauville score has predictive value for HT. Due to the noticeable impact of high pathological grade on the HT risk, we conducted the subgroup analysis in patients with low/high pathological grade, and found SUV_baseline could still predict HT risk in both low-grade and high-grade subgroups. Multivariate analysis adjusted by FLIPI2 score showed the SUV_baseline (HR 1.065, 95% CI 1.020–1.111) and SUV_end (HR 1.261, 95% CI 1.076–1.478) remained as significant predictors independently of the FLIPI2 score. According to the cut-off determined from the ROC analysis, increased SUV_baseline with a cutoff value of 14.3 and higher SUV_end with a cutoff value of 7.3 were highly predictive of a shorter time to HT.

Conclusions

In follicular lymphoma, quantitative assessment used SUV_max at the pre-treatment and end-of-treatment PET/CT scan may be helpful for early screen out patients at high risk of transformation and guide treatment decisions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02094-5.

The clinical applicability of current prognostic models in follicular lymphoma: A systematic review

The Follicular Lymphoma International Prognostic Index (FLIPI) is widely used for risk stratification of patients with follicular lymphoma (FL). Motivated by evolvement in treatment modalities, several prognostic models for FL have been proposed recently. This systematic review aimed to identify available prognostic models for newly diagnosed FL and discuss their potential limitations. A total of ten studies fulfilled the inclusion criteria. Different clinical, laboratory, radiological, and histopathological findings were combined in prognostic models. The majority of studies developed models from clinical trial cohorts, and most lacked validation in populations treated with current treatment options. Although the FLIPI is the most widely used model for prognostication in FL patients, current prognostic models, including FLIPI, are rarely used in clinical practice for treatment decision-making. Future studies should validate the existing, or develop new prognostic models, to identify which of the current standard treatment options benefit high-risk FL patients the most.

Past, present and future of prognostic scores in follicular lymphoma

Although most follicular lymphoma (FL) patients have prolonged survival, the identification of those at risk of early progression, multiple relapses or histological transformation is essential for the improvement of long-term outcomes. In this sense, a plethora of prognostic indexes have been developed in the last decades. However, determining which one is more accurate and clinically meaningful remains a challenge. Key factors for the external validity of available indexes include characteristics of the study population, treatment intervention, and design of the study. While initial risk scores were composed of clinical, biochemical, and hematological variables, genomic and imaging data have been incorporated in recent years. Despite an obvious step forward in the knowledge of the natural history and biology of FL, predictions remain inaccurate. Further research will likely incorporate information from circulating tumor DNA and artificial intelligence models to refine the prognostic classification of the heterogeneous FL population.

High Basal Maximal Standardized Uptake Value (SUVmax) in Follicular Lymphoma Identifies Patients with a Low Risk of Long-Term Relapse

BACKGROUND

Despite that the unfavorable prognostic role of a high Total Metabolic Tumor Volume (TMTV) in Follicular Lymphoma has been demonstrated, the role of SUV_max alone at baseline PET/CT could have a different prognostic role.

PATIENTS AND METHODS

We performed a retrospective observational monocentric cohort study. All patients affected by FL who underwent a basal PET/CT were included. Two subgroups were identified and compared in terms of PFS and OS: (A) Basal SUV_max ≤ 6; and (B) Basal SUV_max > 6.

RESULTS

Ninety-four patients were included, 34 in group A (36.2%) and 60 in group B (63.8%). The PFS at two years was comparable in the two groups (97%). The five-year PFS was 73.5% for group A and 95% for group B (p 0.005). The five-year PFS in the whole cohort was 87.5%. A clear advantage was confirmed in group A in the absence of other risk factors. Patients with SUV_max ≤ 6 and no risk factors showed a 5-year PFS of 73% against 83% for patients with SUV_max > 6 and at least two risk factors.

CONCLUSION

A high FDG uptake favorably correlated with PFS. A low basal SUV_max reflected a higher rate of late relapse requiring a prolonged follow-up. The basal SUV_max is an approachable parameter with prognostic implications.

3D Model Characterization by 2D and 3D Imaging in t(14;18)-Positive B-NHL: Perspectives for In Vitro Drug Screens in Follicular Lymphoma

Simple Summary

Follicular lymphoma is an indolent B cell lymphoproliferative disorder of transformed follicular center B cells, which accounts for 20–30 percent of all non-Hodgkin lymphoma (NHL) cases. Although huge efforts have been made in the last 10 years, this pathology is still considered as incurable, leaving open the discovery and testing of new therapeutic targets requiring relevant preclinical models. Here, we report a realistic 3D model of t (14;18)-positive B-NHL cell culture (ultra-low attachment (ULA)-multicellular aggregates of lymphoma cells (MALC)), which monitored by state-of-the-art 2D and 3D imaging, allows more robust drug testing.

Abstract

Follicular lymphoma (FL) is an indolent B cell lymphoproliferative disorder of transformed follicular center B cells, which accounts for 20–30 percent of all non-Hodgkin lymphoma (NHL) cases. Great advances have been made to identify the most relevant targets for precision therapy. However, no relevant models for in vitro studies have been developed or characterized in depth. To this purpose, we generated a 3D cell model from t(14;18)-positive B-NHL cell lines cultured in ultra-low attachment 96-well plates. Morphological features and cell growth behavior were evaluated by classical microscopy (2D imaging) and response to treatment with different drugs was evaluated by a high-content analysis system to determine the robustness of the model. We show that the ultra-low attachment (ULA) method allows the development of regular, spherical and viable ULA-multicellular aggregates of lymphoma cells (MALC). However, discrepancies in the results obtained after 2D imaging analyses on drug-treated ULA-MALC prompted us to develop 3D imaging and specific analyses. We show by using light sheet microscopy and specifically developed 3D imaging algorithms that 3D imaging and dedicated analyses are necessary to characterize morphological properties of 3D models and drug effects. This study proposes a new method, but also imaging tools and informatic solutions, developed for FL necessary for future preclinical studies.

Prognosis and risk stratification of peripheral T-cell lymphomas

Peripheral T-cell lymphomas represent a rare heterogeneous group of non-Hodgkin lymphomas with generally worse outcomes with standard chemotherapy compared to B-cell lymphomas. Clinical risk prediction tools at baseline have been shown to be prognostic but generally do not impact clinical decision making. However, improving understanding of the prognostic implications of histology and its molecular underpinnings as well as strategies surrounding the use of CD30 as a predictive biomarker for brentuximab vedotin have led to better understanding of how to risk stratify patients. Baseline, interim, and end of treatment PET/CT as evaluated by the Lugano criteria as well as by baseline metabolic tumor volume have also been shown to be prognostic. The role of minimal residual disease tools such as cell free DNA and T-cell gene receptor sequencing remain active areas of investigation in hopes to develop predictive biomarkers in these rare diseases. This review focuses on strategies used to prognosticate in more common forms of peripheral T-cell lymphoma as well as in extranodal NK/T-cell lymphoma.

High total metabolic tumor volume at baseline predicts survival independent of response to therapy

Early identification of ultra-risk diffuse large B-cell lymphoma (DLBCL) patients is needed to aid stratification to innovative treatment. Previous studies suggested high baseline total metabolic tumor volume (TMTV) negatively impacts survival of DLBCL patients. We analyzed the prognostic impact of TMTV and prognostic indices in DLBCL patients, aged 60 to 80 years, from the phase 3 REMARC study that randomized responding patients to R-CHOP (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) into maintenance lenalidomide or placebo. TMTV was computed on baseline positron emission tomography/computed tomography using the 41% maximum standardized uptake value method; the optimal TMTV cutoff for progression-free (PFS) and overall survival (OS) was determined and confirmed by a training validation method. There were 301 out of 650 evaluable patients, including 192 patients classified as germinal center B-cell-like (GCB)/non-GCB and MYC/BCL2 expressor. Median baseline TMTV was 238 cm3; optimal TMTV cutoff was 220 cm3. Patients with high vs low TMTV showed worse/higher Eastern Cooperative Oncology Group performance status (ECOG PS) ≥2, stage III or IV disease, >1 extranodal site, elevated lactate dehydrogenase, International Prognostic Index (IPI) 3-5, and age-adjusted IPI 2-3. High vs low TMTV significantly impacted PFS and OS, independent of maintenance treatment. Although the GCB/non-GCB profile and MYC expression did not correlate with TMTV/survival, BCL2 >70% impacted PFS and could be stratified by TMTV. Multivariate analysis identified baseline TMTV and ECOG PS as independently associated with PFS and OS. Even in responding patients, after R-CHOP, high baseline TMTV was a strong prognosticator of inferior PFS and OS. Moreover, TMTV combined with ECOG PS may identify an ultra-risk DLBCL population. This trial was registered at www.clinicaltrials.gov as #NCT01122472.

Clinical and Biological Prognostic Factors in Follicular Lymphoma

Follicular lymphoma comprises approximately 20-30% of all cases of B-cell lymphomas. Median survival has improved significantly in the modern era. Prognostic factors include histologic grade, cytogenetics, molecular mutations, the tumor microenvironment, and tumor burden. Clinical prognostic indices are available and increasingly incorporate genetic information. Prognostic factors also arise during the course of treatment. Early progression within 24 months of initial chemoimmunotherapy is an adverse prognostic marker of inferior survival. Other high-risk populations include those with double refractory disease or those with high risk of transformation to diffuse large B-cell lymphoma.

The predictive value of pre-treatment 18F-FDG PET/CT on treatment outcome in early-stage extranodal natural killer/T-cell lymphoma

The diagnostic value of pretreatment ¹⁸F-FDG PET/CT in early-stage extranodal natural killer/T-cell lymphoma (ENKTL) is established, but its prognostic value is still unclear. We conducted ¹⁸F-FDG PET/CT-based quantitative and qualitative analysis as well as assessed related clinical parameters in 50 patients with recently diagnosed ENKTL and treated with methotrexate, etoposide, dexamethasone, and pegaspargase (MESA)-based therapy. Patients were followed-up for 38.6 ± 17.8 months. Six patients died of tumor-related disease, and six patients presented with persistence or recurrence. The estimates of the 2-year OS and PFS for the patients were 90.0% (SE: 4.0%) and 82.0% (SE: 5.0%), respectively. Survival curves were obtained using Kaplan-Meier analysis and compared using log rank test. Based on signifiacnt results of univariate analysis, we selected Epstein-Barr virus DNA (EB-DNA), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for multivariate analysis. Finally, MTV was found to be the significant independent predictor of both OS (p = .038) and PFS (p = .039).

Follicular lymphoma: Update on management and emerging therapies at the dawn of the new decade

Follicular lymphoma is the most common indolent non-Hodgkin lymphoma. Survival has improved over the last several decades, mainly because of the incorporation of the anti-CD20 antibody rituximab into preexisting or rediscovered agents. The disease has a relapsing and remitting pattern, coupled with a risk of transformation into an aggressive lymphoma, and considered incurable for most patients. Next-generation sequencing technologies have increased our understanding of the biology and genetic landscape of the disease, identifying potential druggable targets for treatment. Current prognostic models cannot accurately identify patients at risk of early progression and despite the availability of treatment options for relapsed/refractory disease, rational treatment selection balancing disease control, efficacy with toxicity, and quality of life remain unmet needs. This review provides an overview of biology, prognostication, treatment options, and emerging therapies that provide valid grounds for optimism.

18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography in the diagnosis and follow-up of primary hepatic diffuse large B-cell Lymphoma: A clinical case report

RATIONALE

Primary hepatic lymphoma (PHL) is an extremely rare manifestation of extranodal non-Hodgkin lymphoma. There were few cases about PHL in recent years, while cases using positron emission tomography (PET) modalities for both diagnosis and follow-up were even rare.

PATIENT CONCERNS

A 29-year-old man complaining of dull epigastric pain for 2 weeks.

DIAGNOSIS

The features of liver biopsy and immunohistochemistry were consistent with diffuse large B cell lymphoma. Since there were no other foci of lymphoma on the F-fluoro-2-deoxy-D-glucose (F-FDG) PET/computed tomography (CT) images, the patient was further diagnosed with PHL.

INTERVENTIONS

Since the lesions were mainly confined to the right lobe of liver, partial hepatectomy and radiofrequency ablation were performed. Subsequently, 6 cycles of rituximab, cyclophosphamide, adriamycin, vincristine, dexamethasone regimen were performed.

OUTCOMES

The patient recovered well postoperatively and was discharged 1 week after surgery. Fortunately, the follow-up F-FDG PET/CT scan 36 months later revealed no abnormal FDG uptake, indicating the absence of relapse.

LESSONS

As the superiority in excluding other organ involvement, F-FDG PET/CT should be considered as the preferable imaging modality for the diagnosis and follow-up of PHL. Besides chemotherapy, surgical resection should be considered initially. If radical R0 resection could not be done, partial hepatectomy with radiofrequency ablation may also offer an appropriate alternative treatment.

PET-Derived Quantitative Metrics for Response and Prognosis in Lymphoma

Lymphoma is a potentially curable disease; however, the clinical challenge lies in further improvement of outcomes. PET with fludeoxyglucose is an effective imaging tool. PET-derived quantitative metrics have raised significant interest to be used as a prognostic factor to complement clinical parameters for treatment decisions. The most optimized use of these quantitative PET metrics, however, will be possible with the standardization of imaging procedures. In this article, we review the technical and methodological considerations related to PET-derived quantitative metrics, and the relevant published data to emphasize the potential value of these metrics in patient prognosis and treatment response in lymphoma.

Follicular lymphoma

Follicular lymphoma (FL) is a systemic neoplasm of the lymphoid tissue displaying germinal centre (GC) B cell differentiation. FL represents ~5% of all haematological neoplasms and ~20-25% of all new non-Hodgkin lymphoma diagnoses in western countries. Tumorigenesis starts in precursor B cells and becomes full-blown tumour when the cells reach the GC maturation step. FL is preceded by an asymptomatic preclinical phase in which premalignant B cells carrying a t(14;18) chromosomal translocation accumulate additional genetic alterations, although not all of these cells progress to the tumour phase. FL is an indolent lymphoma with largely favourable outcomes, although a fraction of patients is at risk of disease progression and adverse outcomes. Outcomes for FL in the rituximab era are encouraging, with ~80% of patients having an overall survival of >10 years. Patients with relapsed FL have a wide range of treatment options, including several chemoimmunotherapy regimens, phosphoinositide 3-kinase inhibitors, and lenalidomide plus rituximab. Promising new treatment approaches include epigenetic therapeutics and immune approaches such as chimeric antigen receptor T cell therapy. The identification of patients at high risk who require alternative therapies to the current standard of care is a growing need that will help direct clinical trial research. This Primer discusses the epidemiology of FL, its molecular and cellular pathogenesis and its diagnosis, classification and treatment.

Follicular Lymphoma: Recent and Emerging Therapies, Treatment Strategies, and Remaining Unmet Needs

Follicular lymphoma (FL) is a heterogeneous disease with varying prognosis owing to differences in clinical, laboratory, and disease parameters. Although generally considered incurable, prognosis for early- and advanced-stage disease has improved because of therapeutic advances, several of which have resulted from elucidation of the biologic and molecular basis of the disease. The choice of treatment for FL is highly dependent on patient and disease characteristics. Several tools are available for risk stratification, although limitations in their routine clinical use exist. For limited disease, treatment options include radiotherapy, rituximab monotherapy or combination regimens, and surveillance. Treatment of advanced disease is often determined by tumor burden, with surveillance or rituximab considered for low tumor burden and chemoimmunotherapy for high tumor burden disease. Treatment for relapsed or refractory disease is influenced by initial first-line therapy and the duration and quality of the response. Presently, there is no consensus for treatment of patients with early or multiply relapsed disease; however, numerous agents, combination regimens, and transplant options have demonstrated efficacy. Although the number of therapies available to treat FL has increased together with an improved understanding of the underlying biologic basis of disease, the best approach to select the most appropriate treatment strategy for an individual patient at a particular time continues to be elucidated. This review considers prognostication and the evolving treatment landscape of FL, including recent and emergent therapies as well as remaining unmet needs. IMPLICATIONS FOR PRACTICE: In follicular lymphoma, a personalized approach to management based on disease biology, patient characteristics, and other factors continues to emerge. However, application of current management requires an understanding of the available therapeutic options for first-line treatment and knowledge of current development in therapies for previously untreated and for relapsed or refractory disease. Thus, this work reviews for clinicians the contemporary data in follicular lymphoma, from advances in characterizing disease biology to current treatments and emerging novel therapies.

Progression of Disease Within 24 Months in Follicular Lymphoma Is Associated With Reduced Intratumoral Immune Infiltration

PURPOSE

Understanding the immunobiology of the 15% to 30% of patients with follicular lymphoma (FL) who experience progression of disease within 24 months (POD24) remains a priority. Solid tumors with low levels of intratumoral immune infiltration have inferior outcomes. It is unknown whether a similar relationship exists between POD24 in FL.

PATIENTS AND METHODS

Digital gene expression using a custom code set—five immune effector, six immune checkpoint, one macrophage molecules—was applied to a discovery cohort of patients with early- and advanced-stage FL (n = 132). T-cell receptor repertoire analysis, flow cytometry, multispectral immunofluorescence, and next-generation sequencing were performed. The immune infiltration profile was validated in two independent cohorts of patients with advanced-stage FL requiring systemic treatment (n = 138, rituximab plus cyclophosphamide, vincristine, prednisone; n = 45, rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone), with the latter selected to permit comparison of patients experiencing a POD24 event with those having no progression at 5 years or more.

RESULTS

Immune molecules showed distinct clustering, characterized by either high or low expression regardless of categorization as an immune effector, immune checkpoint, or macrophage molecule. Low programmed death-ligand 2 (PD-L2) was the most sensitive/specific marker to segregate patients with adverse outcomes; therefore, PD-L2 expression was chosen to distinguish immune infiltration^HI (ie, high PD-L2) FL biopsies from immune infiltration^LO (ie, low PD-L2) tumors. Immune infiltration^HI tissues were highly infiltrated with macrophages and expanded populations of T-cell clones. Of note, the immune infiltration^LO subset of patients with FL was enriched for POD24 events (odds ratio [OR], 4.32; c-statistic, 0.81; P = .001), validated in the independent cohorts (rituximab plus cyclophosphamide, vincristine, prednisone: OR, 2.95; c-statistic, 0.75; P = .011; and rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone: OR, 7.09; c-statistic, 0.88; P = .011). Mutations were equally proportioned across tissues, which indicated that degree of immune infiltration is capturing aspects of FL biology distinct from its mutational profile.

CONCLUSION

Assessment of immune-infiltration by PD-L2 expression is a promising tool with which to help identify patients who are at risk for POD24.

Prognostic values of baseline, interim and end-of therapy 18F-FDG PET/CT in patients with follicular lymphoma

Purpose

In the present study, we aimed to investigate the role of baseline, interim and end-of treatment positron emission tomography/computed tomography (PET/CT) in assessing the prognosis of follicular lymphoma (FL).

Methods

A total of 84 FL patients were retrospectively analyzed in this study. Baseline (n=59), interim (n=24, after 2–4 cycles) and end-of treatment (n=43) PET/CT images were re-evaluated, and baseline maximum standardized uptake value (SUV_max), total metabolic tumor volume (tMTV) and total lesion glycolysis (TLG) were recorded. Interim (I-PET) and end-of treatment (E-PET) PET/CT responses were interpreted by Deauville five-point scale (D-5PS) and International Harmonization Project criteria (IHP). Survival curves were calculated by Kaplan-Meier curves, and differences between groups were compared by log-rank test.

Results

The 2-year progression-free survival (PFS) of the high- and low-TLG groups was 57.14% and 95.56%, respectively (p=0.0001). The 2-year overall survival (OS) of the high- and low-TLG groups was 62.50% and 100%, respectively (p<0.0001). Multivariate analysis showed that TLG was an independent prognostic factor for PFS (p=0.001, HR=6.577, 95% CI=2.167–19.960) and OS (p=0.030, HR=19.291, 95% CI =2.689–137.947). Besides, Eastern Cooperative Oncology Group (ECOG) was the independent prognostic factor for OS (HR=8.924, 95% CI=1.273–62.559, p=0.028). Interim PET results based on D-5PS or IHP criteria were not significantly correlated with PFS (all p>0.05). However, E-PET results using D-5PS and IHP criteria were statistically significant (p=0.0001 and p=0.006). The D-5PS showed stronger prognostic value compared with IHP criteria. The optimal cutoff value of ΔSUV_max% was 66.95% according to I-PET and 68.97% according to E-PET. However, only the ΔSUV_max% from the baseline to the end-of therapy yielded statistically significant results in the prediction of PFS (p=0.0002).

Conclusion

Our findings indicated that the baseline TLG and E-PET results were significantly associated with prognosis in patients with FL.

How I manage patients with follicular lymphoma

Recent advances in the treatment of follicular lymphoma (FL) have provided insight into molecular and biological influences on pathogenesis and prognosis. Additionally, numerous available treatment strategies for both newly diagnosed and relapsed disease require thoughtful consideration of patient selection to avoid the burden of overtreatment and toxicities. This review provides a broad overview on our approach to managing patients with low grade FL.

Time to Prepare for Risk Adaptation in Lymphoma by Standardizing Measurement of Metabolic Tumor Burden

Increased tumor burden is associated with inferior outcomes in many lymphoma subtypes. Surrogates of tumor burden that are easy to measure, such as the maximum tumor dimension of the bulkiest lesion on CT, have been used as prognostic indices for many years. Recently, total metabolic tumor volume (MTV) and tumor lesion glycolysis have emerged as promising and robust biomarkers of outcome in various lymphomas. The median MTV and the optimal cutoffs to separate patients into risk groups in a study population are, however, highly dependent on the population characteristics and the delineation method used to outline tumor on the PET image. This issue has precluded the use of MTV for risk stratification in trials and clinical practice. Standardization of the methodology is timely to allow the potential for risk adaptation to be explored in addition to response adaptation using PET. Meetings between representatives from research groups active in the field were held under the auspices of the PET International Lymphoma and Myeloma Workshop. A summary of those discussions, which included a review of the literature and a practical assessment of methods used for outlining, including various software options, is presented. Finally, a proposal is made to perform a technical validation of MTV measurement enabling benchmark reference ranges to be derived for published delineation approaches used for outlining with various software. This process would require collation of representative imaging data sets of the most common lymphoma subtypes; agreement on pragmatic criteria for the selection of lesions; generation of a range of MTVs, with consensus to be reached on final contours in a training set; and development of automated software solutions with a set of minimum functionalities to reduce measurement variability. Methods developed in the above training exercise could then be applied to another data set, with a final set of contours and values generated. This final data set would provide a benchmark against which end-users could test their ability to measure MTVs that are consistent with expected values. The data set and automated software solutions could be shared with manufacturers with the aim of including these in standard workflows to allow standardization of MTV measurement across the world.

Recent advances in the first-line treatment of follicular non-Hodgkin lymphoma

Follicular lymphoma (FL) is the most common type of indolent B-cell lymphoma. Twenty years ago, FL was considered an indolent lymphoma with a long survival time but without a high rate of complete remission with chemotherapies. The use of rituximab has improved the response and survival of patients with this lymphoma. More recently, development of biological knowledge and use of targeted drugs have offered new perspectives, including improvement of response rates and survival with chemo-free treatment strategies. In 2019, patients have a 10-year overall survival probability of over 70%. Histological transformation to more aggressive lymphoma and treatment relapses remain a medical challenge, especially for patients relapsing within two years. This article will review the recent advances in the treatment of FL. As the use of new drugs is directly related to the development of biological aspects, we will first summarize recent advances in biological aspects of FL.

How I treat early-relapsing follicular lymphoma

Follicular lymphoma (FL) is the most frequently occurring indolent non-Hodgkin lymphoma, with generally favorable outcomes but a variable clinical course. Recent studies have elucidated the consistent and reproducible frequency of early disease progression in FL, occurring in ∼20% of patients. Relapse of FL within 24 months of chemoimmunotherapy (POD24) is now established as a robust marker of poor survival, leading to increased risk of death. Currently, there is no established method of identifying patients at risk for early disease progression at the time of their FL diagnosis. However, numerous studies worldwide are investigating clinical, pathologic, and radiographic biomarkers to help predict POD24, thereby improving subsequent outcomes and adapting therapy based on individual risk. There is also a paucity of standardized treatments for patients with POD24, but investigations are ongoing testing novel targeted therapies and autologous stem cell transplantation strategies. This review provides an overview of early-relapsing FL and our approach to patient management based on recent available data.

Novel treatment approaches and future perspectives in follicular lymphoma

Follicular lymphoma (FL) is a common B-cell malignancy characterized by relatively indolent growth and incurability with an expected lifetime course of serial intermittent treatment courses. Many patients with FL have lives shortened by the disease and despite a relatively favorable prognosis relative to other incurable systemic malignancies, optimal management of FL has not been achieved. This review focuses on identifying both patients for whom novel therapies might be most beneficial as well as systematically reviewing novel strategies at various levels of investigation. Prognostic markers incorporating clinical measurements and tumor genetics are discussed, yet at the time of diagnosis do not yet powerfully discriminate patients for whom specific strategies are beneficial. Reassessment of prognosis after evaluating the response to initial therapy is the most powerful identifier of those in need of novel management strategies. For initial therapy of high burden systemic disease, anti-CD20 antibody along with chemotherapy or immunomodulators all offer relatively similar effects on overall survival with subtly different effects on progression-free survival and quality of life. Several new agents currently under investigation in the upfront setting are discussed. Perhaps the best testing ground for novel therapies is in patients with early relapse following initial immunochemotherapy. Ongoing research in multiple therapy classes including, novel monoclonal antibodies, antibody drug conjugates, immunomodulatory agents, intracellular pathway inhibitors, immune checkpoint inhibitors, and epigenetic regulators are discussed herein.

Tumor fragmentation estimated by volume surface ratio of tumors measured on 18F-FDG PET/CT is an independent prognostic factor of diffuse large B-cell lymphoma

INTRODUCTION

Our aim was to study the prognostic value of two new ¹⁸F-FDG PET biomarkers in diffuse large B-cell lymphoma (DLBCL). We examined the total tumor surface (TTS), describing the tumor-host interface, and the tumor volume surface ratio (TVSR), corresponding to the ratio between the total metabolic tumor volume (TMTV) and TTS, describing the tumor fragmentation.

METHODS

We retrospectively included 215 patients with DLBCL. Patients underwent initial ¹⁸F-FDG PET/CT before R-CHOP (73%) or intensified R-CHOP (R-ACVBP) regimens (27%). The TMTV was measured using a fixed threshold value of 41% of SUVmax. To calculate TTS and TVSR, the surface was measured using an in-house software based on the marching cube algorithm. Spearman's rank correlation coefficient (ρ) was computed between TMTV, TTS, and TVSR, and ROC analysis was performed. Survival functions at 5 years were studied using a Kaplan-Meier method and uni/multivariate Cox analysis.

RESULTS

TVSR was poorly correlated with TMTV (ρ = 0.5) and TTS (ρ = 0.26), while TTS was highly correlated with TMTV (ρ = 0.94) and was, therefore, excluded from the analysis. TMTV had the highest area under the ROC curve (0.711) and the best sensitivity (0.797), while TVSR had the best specificity (0.745). The optimal cut-off values to predict 5-year OS were 222 cm³ for TMTV and 6.0 mm for TVSR. Patients with high TMTV and TVSR had significantly worse prognosis in Kaplan-Meier and Cox univariate analysis. In a multivariate Cox analysis combining the International Prognostic Index (IPI), the type of chemotherapy, TMTV, and TVSR, all parameters were independent and significant prognostic factors (HR [95%CI]: IPI 1.4 [1.1-1.8], type of chemotherapy 4.5 [2.0-10.5], TMTV 2.8 [1.4-5.5], TVSR 2.1 [1.3-3.4]). A synergistic effect between TMTV and TVSR was observed in a Kaplan-Meier analysis combining the two parameters.

CONCLUSIONS

TVSR measured on the initial ¹⁸F-FDG PET is an independent prognostic factor in DLBCL and has an additional prognostic value when combined with TMTV, IPI score and chemotherapy.