FDG PET/CT Response Assessment Criteria for Patients with Hodgkin's and Non-Hodgkin's Lymphoma at End of Therapy: A Multiparametric Approach

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.

Comparison between diffusion-weighted magnetic resonance and positron-emission tomography in the evaluation of treated lymphomas with mediastinal involvement

Background

The persistence of residual tissue after treatment is frequent in patients with mediastinal lymphomas and it is often characterized by 18F-Flurodeoxyglucose Positron Emission Tomography (18F-FDG PET) uptake. This study aims to investigate the usefulness of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) sequence in residual tissues of treated mediastinal lymphomas and to compare it with 18F-FDG PET-CT.

Results

We included 21 patients with mediastinal Hodgkin and non-Hodgkin lymphomas who showed residual masses on PET-CT imaging at end of treatment and underwent DWIBS-Magnetic Resonance Imaging (MRI). SUVmax and Apparent Diffusion Coefficient (ADC) values of residual masses were assessed quantitatively, including measurement of mean ADC. 15 patients showed radiotracer uptake at 18F-FDG PET-CT, among them only 3 had positive DWIBS-MRI with low ADC values (median value: 0.90 mm2/s). The mediastinal biopsy in these 3 “double positive” patients confirmed pathological residual tissue. All the patients with positive 18F-FDG PET-CT but negative DWIBS-MRI (n = 18) with high ADC values (median value: 2.05 mm2/s) were confirmed negative by biopsy.

Conclusions

DWIBS-MRI examination combined with ADC measurement allowed to discriminate pathological and non-pathological residual tissue in patients with treated mediastinal lymphoma. These preliminary results seem to pave the way for a leading role of the MRI which could be a useful alternative to the 18F-FDG PET/CT.

Positron emission tomography/computed tomography in the management of Hodgkin and B-cell non-Hodgkin lymphoma: An update

¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is now an integral part of lymphoma staging and management. Because of its greater accuracy compared with CT alone, PET/CT is currently routinely performed for staging and for response assessment at the end of treatment in the vast majority of FDG-avid lymphomas and is the cornerstone of response classification for these lymphomas according to the Lugano classification. Interim PET/CT, typically performed after 2 to 4 of 6 to 8 chemotherapy/chemoimmunotherapy cycles with or without radiation, is commonly performed for prognostication and potential treatment escalation or de-escalation early in the course of therapy, a concept known as response-adapted or risk-adapted treatment. Quantitative PET is an area of growing interest. Metrics, such as the standardized uptake value, changes (Δ) in the standardized uptake value, metabolic tumor volume, and total lesion glycolysis, are being investigated as more reproducible and potentially more accurate predictors of response and prognosis. Despite the progress made in standardizing the use of PET/CT in lymphoma, challenges remain, particularly with respect to its limited positive predictive value, emphasizing the need for more specific molecular probes. This review highlights the most relevant applications of PET/CT in Hodgkin and B-cell non-Hodgkin lymphoma, its strengths and limitations, as well as recent efforts at implementing PET/CT-based metrics as promising tools for precision medicine.

Long-term results of PET-guided radiation in patients with advanced-stage diffuse large B-cell lymphoma treated with R-CHOP

Consolidative radiation therapy (RT) for advanced-stage diffuse large B-cell lymphoma (DLBCL) remains controversial, with routine practice continuing to include RT in patients with initial bulky disease or residual masses. Positron emission tomography (PET)-computed tomography is a sensitive modality for detecting the presence of residual disease at the end of treatment (EOT). A PET-guided approach to selectively administering RT has been the policy in British Columbia since 2005. Patients with advanced-stage DLBCL diagnosed from 1 January 2005 to 1 March 2017 and treated with at least 6 cycles of R-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone plus rituximab), who underwent EOT PET, were included in this analysis. Those with complete metabolic response (PET-negative [PET-NEG]) were observed; those with PET-positive (PET-POS) scans were offered consolidative RT, when feasible. Of the patient records reviewed, 723 were identified, with median follow-up of 4.3 years: 517 (72%) were PET-NEG; 206 (28%) were PET-POS. Time to progression (TTP) and overall survival (OS) at 3 years were 83% vs 56% and 87% vs 64%, in patients with PET-NEG and PET-POS scans, respectively. PET-POS patients with nonprogressing disease treated with consolidative RT (109 and 206; 53%) had outcomes approaching those of PET-NEG patients, with 3-year estimates of 76% and 80% for TTP and OS. PET-NEG patients who had bulky disease (≥10 cm) at diagnosis had outcomes indistinguishable from those without bulk, despite the omission of RT. These data suggest that patients with advanced-stage DLBCL who are PET-NEG at EOT and receive no RT have excellent outcomes. 18F-fluorodeoxyglucose-PET can reliably guide selective administration of consolidative RT, even in patients with initially bulky disease.

PET/CT in pediatric oncology

The use of PET/CT in adult oncology has been consolidated by several and authoritative multicentric studies, metanalyses and systematic reviews. International guidelines help everyday nuclear medicine specialists, oncologists and radiologists in choosing the most suitable diagnostic path for each patient. Classifications based on traditional imaging and PET/CT findings define the most appropriate treatment and can predict the outcome for different types of malignancies. However, compared to adult patients the use of PET/CT in pediatric oncology is often burdened by lack of systematic and large multicentric studies and consequently accurate and precise guidelines. The cause of this shortage of large trials may be attributed to the rarity of these neoplasms and to the fear of long-term radiation effects on this peculiar category of patients. The aim of this article is to review the applications of PET/CT for imaging the most common pediatric neoplasms.

Predictive Value of Interim and End-of-Therapy 18F-FDG PET/CT in Patients with Follicular Lymphoma

PURPOSE

18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is the standard imaging modality for response evaluation in FDG-avid lymphoma, but the prognostic value is not established in follicular lymphoma (FL). This study investigated the prognostic value of Deauville 5-point scale (D5PS) from paired interim PET/CT (PETInterim) and end-of-induction therapy PET/CT (PETEOI) in patients with FL.

METHODS

FL staging and response assessment PET/CT images from 2013 to 2015 were retrospectively reviewed. PETInterim was performed 3 or 4 cycles after chemotherapy and PETEOI after 6 or 8 cycles. D5PS scores of 1, 2, and 3 were considered as negative (-), and scores 4 and 5 were considered as positive (+). Statistical analysis was done using Cox regression analysis, Kaplan-Meier survival analysis, and the log-rank test.

RESULTS

Thirty-three patients with set of baseline, interim, and end-of-induction therapy PET/CT studies were included. Ten patients (30.3%) had progression. The median progression-free survival (PFS) was 38.8 months (range 3.5-72.7 months). On PETInterim, 23 patients were negative and 10 were positive. On PETEOI scans, 29 patients were negative, and 4 were positive. On multivariate analysis, PETEOI(-) was associated with longer PFS. PETInterim(+) and PETEOI(+) patients had a significantly shorter PFS than PETInterim(-) patients (39.9 months, 95% confidence interval [CI] 23.0-56.9, versus 55.5 months, 95% CI 49.7-61.2, p = 0.005) and PETEOI(-) patients (14.2 months, 95% CI 8.5-19.8, versus 60.5 months, 95% CI 52.1-69.0, p < 0.001).

CONCLUSION

For patients with FL, PETInterim and PETEOI response is predictive of PFS, and PETEOI(+) is an independent prognostic factor for progression of FL.

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.

Application of Quantitative Indexes of FDG PET to Treatment Response Evaluation in Indolent Lymphoma

Purpose

Although ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a standard imaging modality for response evaluation in FDG-avid lymphoma, there is a controversy using FDG PET in indolent lymphoma. The purpose of this study was to investigate the effectiveness of quantitative indexes on FDG PET in response evaluation of the indolent lymphoma.

Methods

Fifty-seven indolent lymphoma patients who completed chemotherapy were retrospectively enrolled. FDG PET/computed tomography (CT) scans were performed at baseline, interim, and end of treatment (EOT). Response was determined by Lugano classification, and progression-free survival (PFS) by follow-up data. Maximum standardized uptake value (SUV_max), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured in the single hottest lesion (target A) or five hottest lesions (target B). Their efficacies regarding response evaluation and PFS prediction were evaluated.

Results

On EOT PET, SUV_max, and MTV of both targets were well associated with visual analysis. Changes between initial and EOT PET were not significantly different between CR and non-CR groups. On interim PET, SUV_max, and %ΔSUV_max in both targets were significantly different between CR and non-CR groups. For prediction of PFS, most tested indexes were significant on EOT and interim PET, with SUV_max being the most significant prognostic factor.

Conclusion

Quantitative indexes of FDG PET are well associated with Lugano classification in indolent lymphoma. SUV_max measured in the single hottest lesion can be effective in response evaluation and prognosis prediction on interim and EOT PET.

Optimisation of metabolic criteria in the prognostic assessment in patients with lymphoma. A multicentre study

OBJECTIVE

To compare sensitivity, specificity and predictive value of Deauville score (DS) vs. ΔSUVmax in interim-treatment PET (iPET) and end-treatment PET (ePET), in patients with diffuse large B cell lymphoma (DLBCL), Hodgkin lymphoma (HL), and follicular lymphoma (FL).

METHOD

Retrospective longitudinal multicentre study including 138 patients (46 DLBCL, 46 HL, 46 FL), on whom 3 ¹⁸F-FDG PET/CT were performed: baseline, iPET, and ePET. Visual (DS) and semi-quantitative (ΔSUVmax) parameters were determined for iPET and ePET. Predictive value was determined in relation to disease-free interval.

RESULTS

Statistical analysis. iPET for DLBCL, HL, and FL: 1) sensitivity of DS: 76.92/83.33/61.53%; specificity: 78.78/85/81.81%; 2) sensitivity of ΔSUVmax: 53.84/83.33/61.53%; specificity: 87.87/87.50/78.78%. ePET for DLBCL, HL and FL: 1) sensitivity of DS: 61.53/83.33/69.23%; specificity: 90.90/85/87.87%; 2) sensitivity of ΔSUVmax: 69.23/83.33/69.23%; specificity: 90.90/87.50/84.84%. Predictive assessment. iPET study: in DLBCL, DS resulted in 10.3% recurrence of negative iPET, and 17.1% in ΔSUVmax at disease-free interval; in HL, both parameters showed a 2.8% recurrence of negative iPET; in FL, DS resulted in 15.6% recurrence of negative iPET, and 16.1% in ΔSUVmax, with no statistical significance. ePET study: in DLBCL, DS resulted in 14.3% recurrence of negative ePET, and 11.8% in ΔSUVmax at disease-free interval; in HL and FL, both methods showed 2.8 and 12.5% recurrence in negative ePET, respectively.

CONCLUSION

DS and ΔSUVmax did not show significant differences in DLBCL, HL and FL. Their predictive value also did not show significant differences in HL and FL. In DLBCL, DS was higher in iPET, and ΔSUVmax in ePET.