Impact of Q.Clear reconstruction algorithm on the interpretation of PET/CT images in patients with lymphoma

BackgroundQ.Clear is a new Bayesian penalized-likelihood PET reconstruction algorithm. It has been documented that Q.Clear increases the SUVmax values of different malignant lesions.PurposeSUVmax values are crucial for the interpretation of PET/CT images in patients with lymphoma, particularly when the early and final responses to treatment are evaluated. The aim of the study was to systematically analyse the impact of the use of Q.Clear on the interpretation of PET/CT in patients with lymphoma.MethodsA total of 280 18F-FDG PET/CT scans in patients with lymphoma were performed for staging (sPET), for early treatment response (iPET), after the end of treatment (ePET) and when a relapse of lymphoma was suspected (rPET). Scans were separately reconstructed with two algorithms, Q.Clear and OSEM, and further compared.ResultsThe stage of lymphoma was concordantly diagnosed in 69/70 patients with both algorithms on sPET. Discordant assessment of the Deauville score (p < 0.001) was found in 11 cases (15.7%) of 70 iPET scans and in 11 cases of 70 ePET scans. An upgrade from a negative to a positive scan by Q.Clear occurred in 3 cases (4.3%) of iPET scans and 7 cases (10.0%) of ePET scans. The results of all 70 rPET scans were concordant. The SUVmax values of the target lymphoma lesions measured with Q.Clear were higher than those measured with OSEM in 88.8% of scans.ConclusionAlthough the Q.Clear algorithm may alter the interpretations of PET/CT in only a small proportion of patients, we recommend using standard OSEM reconstruction for the assessment of treatment response.

BackgroundTo compare the changes in quantitative parameters and the size and degree of 18F-fluorodeoxyglucose ([18F]FDG) uptake of malignant tumor lesions between Bayesian penalized-likelihood (BPL) and non-BPL reconstruction algorithms.MethodsPositron emission tomography/computed tomography images of 86 malignant tumor lesions were reconstructed using the algorithms of ordered subset expectation maximization (OSEM), OSEM + time of flight (TOF), OSEM + TOF + point spread function (PSF), and BPL. [18F]FDG parameters of maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume (MTV), total lesion glycolysis (TLG), and signal-to-background ratio (SBR) of these lesions were measured. Quantitative parameters between the different reconstruction algorithms were compared, and correlations between parameter variation and lesion size or the degree of [18F]FDG uptake were analyzed.ResultsAfter BPL reconstruction, SUVmax, SUVmean, and SBR were significantly increased, MTV was significantly decreased. The difference values of %ΔSUVmax, %ΔSUVmean, %ΔSBR, and the absolute value of %ΔMTV between BPL and OSEM + TOF were 40.00%, 38.50%, 33.60%, and 33.20%, respectively, which were significantly higher than those between BPL and OSEM + TOF + PSF. Similar results were observed in the comparison of OSEM and OSEM + TOF + PSF with BPL. The %ΔSUVmax, %ΔSUVmean, and %ΔSBR were all significantly negatively correlated with the size and degree of [18F]FDG uptake in the lesions, whereas significant positive correlations were observed for %ΔMTV and %ΔTLG.ConclusionThe BPL reconstruction algorithm significantly increased SUVmax, SUVmean, and SBR and decreased MTV of tumor lesions, especially in small or relatively hypometabolic lesions.

BackgroundHepatocellular carcinoma (HCC) is considered as one of the major causes of morbidity and mortality worldwide. Microwave ablation (MWA) is a widely used treatment option having less morbidity and complications as compared with surgery and liver transplantation. MRI is the most widely used modality in the assessment of treatment response after MWA. Currently, LI-RADS v2018 algorithm is considered the cornerstone in daily clinical practice for assessment of the treatment response after locoregional therapy. The aim of the study was to assess the role of dynamic MRI and diffusion imaging in the assessment of treatment response and detection of tumor viability following microwave ablation therapy of HCC according to LI-RADS v2018 treatment response algorithm.ResultsThis retrospective study was performed over 45 HCC lesions underwent MWA as the only therapeutic procedure and followed up by dynamic MRI with diffusion images and then classified according to the LI-RADS treatment response criteria into LR-TR viable and LR-TR nonviable groups. All the malignant lesions found in this study showed arterial phase hyperenhancment (APHE), whether in the early or late arterial phases. Delayed washout was found in all malignant lesions as well. In the diffusion analysis, the mean ADC value for the malignant lesions was 0.900 ± 0.126 × 10-3 mm2/s, while the mean ADC of the treatment-related specific benign parenchymal enhancement was 1.284 ± 0.129 × 10-3 mm2/s with a significant statistical difference in between (P = 0.0001) and a cutoff value of 1.11 × 10-3 mm2/s. Our findings showed that the dynamic MRI has 100% sensitivity, 93.5% specificity, 87.5% PPV, and 100% NPV in the detection of tumoral activity compared with 71.43% sensitivity, 93.55% specificity, 83.33% PPV, and 87.88% NPV for diffusion images.ConclusionLI-RADS 2018 provides a treatment response algorithm superior to the previously used assessment criteria. MRI with dynamic contrast-enhanced technique and diffusion imaging provide a powerful tool in the evaluation of treatment response after microwave ablation of hepatocellular carcinoma using the LI-RADS treatment response criteria and is considered a reliable method in differentiating between the recurrent or residual malignant lesions and the posttreatment benign liver changes.

In recent years, various approaches to overcome the problems associated with iterative statistical image reconstruction methods have been investigated, including issues such as slow convergence rate, costly computational time and nonuniform correction efficiency. A multiscale Bayesian image reconstruction algorithm based on a 1-D wavelet technique is proposed. In this approach, the authors first apply a wavelet transform to the sinogram measurements, which yields a multiresolution object representation. The image is reconstructed at the corresponding grid by the Bayesian image reconstruction algorithm for each scale level in the frequency space; the backprojector is also modified to match each corresponding resolution scale. After the low-frequency components of the image have been recovered sufficiently on the coarser scale level, the resulted image is used as the starting point for the finer level at a new iteration. An important feature in the authors' new approach is that the wavelet decomposition is carried out in the sinogram space, while multiple grids are also used in the reconstructed image space.

Dual time point [18F]Flurodeoxyglucose (FDG) Positron Emission Tomography (PET)/Computed Tomography (CT) with water gastric distension in differentiation between malignant and benign gastric lesions

We present a Bayesian velocity field reconstruction algorithm that performs the reconstruction of the mass density field using only peculiar velocity data. Our method consistently accounts for the inhomogeneous Malmquist (IHM) bias using analytical integration along the line of sight. By testing our method on a simulation, we show that our method gives an unbiased reconstruction of the velocity field. We show that not accounting for the IHM bias can lead to significant biases in the Bayesian reconstructions. We applied our method to a peculiar velocity data set consisting of the SFI++ and 2MTF Tully–Fisher catalogues and the A2 supernovae compilation, thus obtaining a novel velocity reconstruction in the local Universe. Our velocity reconstructions have a cosmological power spectrum consistent with the theoretical expectation. Furthermore, we obtain a full description of the uncertainties on reconstruction through samples of the posterior distribution. We validate our velocity reconstruction of the local Universe by comparing it to an independent reconstruction using the 2M++ galaxy catalogue, obtaining good agreement between the two reconstructions. Using Bayesian model comparison, we find that our velocity model performs better than the adaptive kernel smoothed velocity with the same peculiar velocity data. However, our velocity model does not perform as well as the velocity reconstruction from the 2M++ galaxy catalogue, due to the sparse and noisy nature of the peculiar velocity tracer samples. The method presented here provides a way to include peculiar velocity data in initial condition reconstruction frameworks.

Block sequential regularized expectation maximization (BSREM) is a Bayesian penalized-likelihood reconstruction algorithm for PET, which reaches full convergence without the detriment of deteriorating the image quality by noise. Therefore, BSREM might have implications particularly for the detection of small lesions, which may be beneficial in melanoma patients. Our case of a 70-year-old man with metastasized malignant melanoma illustrates the impact of such a novel iterative PET reconstruction algorithm. Whereas the lymph node metastases are seen with the latest generation ordered subset expectation maximization reconstruction, the in-transit metastases are identified straightforward only with BSREM reconstruction.

PurposeQ.Clear is a block sequential regularized expectation maximization (BSREM) penalized-likelihood reconstruction algorithm for PET. It tries to improve image quality by controlling noise amplification during image reconstruction. In this study, the noise properties of this BSREM were compared to the ordered-subset expectation maximization (OSEM) algorithm for both phantom and patient data acquired on a state-of-the-art PET/CT.MethodsThe NEMA IQ phantom and a whole-body patient study were acquired on a GE DMI 3-rings system in list mode and different datasets with varying noise levels were generated. Phantom data was evaluated using four different contrast ratios. These were reconstructed using BSREM with different β-factors of 300–3000 and with a clinical setting used for OSEM including point spread function (PSF) and time-of-flight (TOF) information. Contrast recovery (CR), background noise levels (coefficient of variation, COV), and contrast-to-noise ratio (CNR) were used to determine the performance in the phantom data. Findings based on the phantom data were compared with clinical data. For the patient study, the SUV ratio, metabolic active tumor volumes (MATVs), and the signal-to-noise ratio (SNR) were evaluated using the liver as the background region.ResultsBased on the phantom data for the same count statistics, BSREM resulted in higher CR and CNR and lower COV than OSEM. The CR of OSEM matches to the CR of BSREM with β = 750 at high count statistics for 8:1. A similar trend was observed for the ratios 6:1 and 4:1. A dependence on sphere size, counting statistics, and contrast ratio was confirmed by the CNR of the ratio 2:1. BSREM with β = 750 for 2.5 and 1.0 min acquisition has comparable COV to the 10 and 5.0 min acquisitions using OSEM. This resulted in a noise reduction by a factor of 2–4 when using BSREM instead of OSEM. For the patient data, a similar trend was observed, and SNR was reduced by at least a factor of 2 while preserving contrast.ConclusionThe BSREM reconstruction algorithm allowed a noise reduction without a loss of contrast by a factor of 2–4 compared to OSEM reconstructions for all data evaluated. This reduction can be used to lower the injected dose or shorten the acquisition time.

&lt;p dir="ltr"&gt;Pancreatic cancer remains one of the most lethal malignancies, largely due to late diagnosis, complex tumor biology, and limitations of conventional imaging in early detection, lesion characterization, and treatment response assessment. A defining biological feature of pancreatic ductal adenocarcinoma is its dense desmoplastic stroma, dominated by cancer-associated fibroblasts that express fibroblast activation protein. Targeting this stromal component offers a biologically distinct imaging signal compared with conventional morphologic or metabolic approaches and may improve biological lesion characterization in diagnostically challenging settings.&lt;/p&gt;&lt;p dir="ltr"&gt;The overall aim of this thesis was to evaluate the clinical utility of [68Ga]Ga-FAPI- 46 positron emission tomography/computed tomography (PET/CT) for imaging- based assessment of pancreatic cancer in selected clinically relevant decision- making contexts. Four substudies, embedded within a prospective Phase II clinical trial, investigated tumor characterization and diagnostic performance, temporal uptake behavior and differentiation from inflammatory disease, optimization of acquisition protocols and image quality, as well as evaluation of treatment response following neoadjuvant therapy.&lt;/p&gt;&lt;p dir="ltr"&gt;Paper I investigated the diagnostic accuracy of FAPI PET/CT in patients with suspected pancreatic or periampullary tumors scheduled for surgical exploration. FAPI PET/CT demonstrated high sensitivity and excellent lesion conspicuity for malignant disease, with particular value in cases where conventional imaging was equivocal. Quantitative uptake thresholds enabled reliable differentiation between malignant and benign pathology in this surgically verified cohort, supporting the role of stromal-targeted imaging as a complementary diagnostic tool in preoperative scenarios with high diagnostic uncertainty.&lt;/p&gt;&lt;p dir="ltr"&gt;Paper II addressed methodological optimization by evaluating whether PET acquisition time could be reduced without compromising image quality or quantitative reliability. Visual grading and quantitative analyses showed that three-minute acquisitions preserved diagnostic image quality, standardized uptake values, and lesion-to-background ratios, supporting the feasibility of streamlined protocols suitable for routine clinical implementation and advanced imaging strategies.&lt;/p&gt;&lt;p dir="ltr"&gt;Paper III explored temporal uptake patterns to improve differentiation between pancreatic cancer and chronic pancreatitis. While early single-time-point uptake demonstrated overlap between malignant and inflammatory lesions, relative changes in uptake over time provided superior discrimination. Relative SUVmax change achieved the highest diagnostic performance, with delayed imaging offering incremental value. A 60-minute relative change metric retained high discriminatory performance at a clinically practical and patient-convenient time point.&lt;/p&gt;&lt;p dir="ltr"&gt;Paper IV evaluated the role of post-neoadjuvant FAPI PET/CT for treatment response assessment and perivascular evaluation in a clinically responder- selected cohort. No significant associations were observed between whole- tumor FAPI uptake and histopathological TRG, reflecting both cohort characteristics and the biological persistence of stromal activation after therapy. However, exploratory vessel-level analyses demonstrated a directional relationship between perivascular FAPI uptake and histopathologic vascular involvement, suggesting potential complementary value in evaluating equivocal vascular findings after neoadjuvant treatment.&lt;/p&gt;&lt;p dir="ltr"&gt;In conclusion, [68Ga]Ga-FAPI-46 PET/CT provides high diagnostic sensitivity and conspicuity in untreated pancreatic cancer, particularly in cases where routine clinical imaging is inconclusive. Acquisition time optimization supports practical clinical implementation, and temporal imaging enhances lesion characterization where fibro-inflammatory overlap limits specificity. Conversely, isolated post- therapy FAPI PET snapshots may struggle to accurately reflect histopathologic regression, indicating the importance of baseline or longitudinal imaging strategies in response assessment. Together, the findings define clinically relevant contexts in which stromal-targeted PET adds value to current pancreatic cancer imaging pathways and establish a foundation for future prospective and longitudinal studies.&lt;/p&gt;&lt;h3 dir="ltr"&gt;List of scientific papers&lt;/h3&gt;&lt;p dir="ltr"&gt;I. &lt;b&gt;Rasinski P,&lt;/b&gt; af Buren S, Holstensson M, Nilsson T, Loizou L, Tran TA, Sparrelid E, Löhr JM, Axelsson R. Tumor Characterization by [68Ga]FAPI-46 PET/CT Can Improve Treatment Selection for Pancreatic Cancer Patients: An Interim Analysis of a Prospective Clinical Trial. J Nucl Med 2023; 64: 1232-1237. &lt;a href="https://doi.org/10.2967/jnumed.123.265481" rel="noreferrer" target="_blank"&gt;https://doi.org/10.2967/jnumed.123.265481&lt;/a&gt;&lt;/p&gt;&lt;p dir="ltr"&gt;II. Nilsson T, &lt;b&gt;Rasinski P,&lt;/b&gt; Smedby Ö, af Buren S, Sparrelid E, Löhr JM, Tran TA, Blomgren A, Tzortzakakis A, Axelsson R, Holstensson M. Acquisition Duration Optimization Using Visual Grading Regression in [68Ga]FAPI-46 PET Imaging of Oncologic Patients. J Nucl Med Technol 2024; 52: 221-228. &lt;a href="https://doi.org/10.2967/jnmt.123.267156" rel="noreferrer" target="_blank"&gt;https://doi.org/10.2967/jnmt.123.267156&lt;/a&gt;&lt;/p&gt;&lt;p dir="ltr"&gt;III. &lt;b&gt;Rasinski P,&lt;/b&gt; Nilsson T, Peillon A, Holstensson M, Tzortzakakis A, Moro CF, Tran TA, Sparrelid E, Löhr JM, Axelsson R. Timing is Everything: Unmasking Pancreatic Cancer with Dual and Multiple-Timepoint [68Ga]Ga-FAPI-46 PET Imaging [Submitted] &lt;/p&gt;&lt;p dir="ltr"&gt;IV. &lt;b&gt;Rasinski P,&lt;/b&gt; Loizou L, Molina Centelles MF, Tzortzakakis A, Peillon A, Søreide K, Sparrelid E, Axelsson R, Ghorbani P. Post-Neoadjuvant FAPI PET/CT in Pancreatic Cancer: Response Assessment and Perivascular Evaluation [Manuscript]&lt;/p&gt;

Objective To evaluate the value of semi-quantitative indices of 68Ga-prostate specific membrane antigen (PSMA)-11 PET/CT in differentiating malignant and benign prostate lesions. Methods From November 2017 to June 2018, 30 patients (age: 52-86 years) who underwent 68Ga-PSMA-11 PET/CT imaging in the Third Affiliated Hospital of Sun Yat-sen University were retrospectively analyzed, and the serum total prostate specific antigen (tPSA) and free prostate specific antigen (fPSA) were examined within 1 week before PET/CT imaging. Semi-quantitative indices of 68Ga-PSMA-11 PET/CT on prostate lesions were measured by automatic segmentation algorithm method, including PSMA-related lesion volume (VPSMA), maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), peak standardized uptake value (SUVpeak) and total lesion uptake value of PSMA (TLUPSMA). The indices were compared between malignant and benign prostate lesions, and the optimal cut-off values for differentiating malignant and benign prostate lesions were obtained by receiver operating characteristic (ROC) curve analysis. Results According to the pathological results, 19 patients had malignant lesions and 11 were with benign diseases. The differences of tPSA, SUVmax, SUVmean, SUVpeak and TLUPSMA between malignant and benign prostate lesions were statistically significant (u values: 17.00-48.00, all P 0.05). The optimal cut-off value of tPSA was 18.30 μg/L for differentiating malignant and benign prostate lesions, with sensitivity of 13/17 (PSA of 2 patients were missing), specificity of 9/11 and area under curve (AUC) of 0.743. The optimal cut-off values of SUVmax, SUVmean and SUVpeak were 5.50, 3.09 and 3.56, respectively, with all corresponding sensitivity of 18/19, all specificity of 9/11, and AUC of 0.902, 0.907 and 0.919, respectively. The optimal cut-off value of TLUPSMA was 54.81 cm3, with sensitivity of 14/19, specificity of 9/11 and AUC of 0.804. Conclusion The semi-quantitative indices of 68Ga-PSMA-11 PET/CT are valuable for differentiating malignant and benign prostate lesions, in which SUVpeak is superior to other indices. Key words: Prostatic neoplasms; Prostate-specific membrane antigen; Isotope labeling; Gallium radioisotopes; Positron-emission tomography; Tomography, X-ray computed; Diagnosis, differential

To evaluate the role of fluorine-18-labeled fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) in various rheumatic diseases and its potential in the early assessment of treatment response in a limited number of patients. This study involved 28 newly diagnosed patients, of these 17 had rheumatoid arthritis (RA) and 11 had seronegative spondyloarthropathy (SSA). In the SSA group, 7 patients had ankylosing spondylitis, 3 had psoriatic arthritis, and one had non-specific SSA. Patients with RA were selected as per the American College of Rheumatology criteria. One hour after FDG injection, a whole body PET scan was performed from the skull vertex to below the knee joints using a GE Advance dedicated PET scanner. Separate scans were acquired for both upper and lower limbs. Post-treatment scans were performed in 9 patients in the RA group (at 6-9 wk from baseline) and in 1 patient with psoriatic arthropathy. The pattern of FDG uptake was analysed visually and quantified as maximum standardized uptake value (SUVmax) in a standard region of interest. Metabolic response on the scan was assessed qualitatively and quantitatively and was correlated with clinical assessment. The qualitative FDG uptake was in agreement with the clinically involved joints, erythrocyte sedimentation rate, C-reactive protein values and the clinical assessment by the rheumatologist. All 17 patients in the RA group showed the highest FDG avidity in painful/swollen/tender joints. The uptake pattern was homogeneous, intense and poly-articular in distribution. Hypermetabolism in the regional nodes (axillary nodes in the case of upper limb joint involvement and inguinal nodes in lower limb joints) was a constant feature in patients with RA. Multiple other extra-articular lesions were also observed including thyroid glands (in associated thyroiditis) and in the subcutaneous nodules. Treatment response was better appreciated using SUVmax values than visual interpretation, when compared with clinical evaluation. Four patients showed a favourable response, while 3 had stable disease and 2 showed disease progression. The resolution of regional nodal uptake (axillary or inguinal nodes based on site of joint involvement) in RA following disease modifying anti-rheumatoid drugs was noteworthy, which could be regarded as an additional parameter for identifying responding patients. In the SSA group, uptake in the affected joint was heterogeneous, low grade and non-symmetrical. In particular, there was intense tendon and muscular uptake corresponding to symptomatic joints. The patients with psoriatic arthritis showed intense FDG uptake in the joints and soft tissue. (18)F-FDG PET accurately delineates the ongoing inflammatory activity in various rheumatic diseases (both at articular and extra-articular sites) and relates well to clinical symptoms. Different metabolic patterns on FDG-PET scanning in RA and SSA can have important implications for their diagnosis and management in the future with the support of larger studies. FDG-PET molecular imaging is also a sensitive tool in the early assessment of treatment response, especially when using quantitative information. With these benefits, FDG-PET could play a pivotal clinical role in the management of inflammatory joint disorders in the future.

Thyroid incidentalomas (TIs) detected on 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) are associated with an increased risk of malignancy, particularly in the presence of focal FDG uptake. While quantitative PET/CT parameters, such as the maximum standardized uptake value (SUVmax), have been extensively studied, current management guidelines primarily rely on nodule size and ultrasonographic features. This study aimed to evaluate whether PET/CT-derived radiological parameters provide additional information for malignancy in FDG-avid TIs. This retrospective single-center study included patients with focal FDG-avid thyroid incidentalomas detected on PET/CT who underwent ultrasonographic evaluation and cytological and/or histopathological confirmation. Demographic characteristics, metabolic parameters derived from PET/CT scans, ultrasonographic findings and anatomical localization were documented. Benign and malignant lesions were compared. Receiver operating characteristic (ROC) analysis was conducted to determine the optimal SUVmax cut-off value and logistic regression analyses were employed to identify variables independently associated with malignancy. A total of 53 patients were included, with 13 (24.5%) having malignant thyroid lesions. Malignant nodules demonstrated significantly higher SUVmax values than benign nodules (p=0.008). ROC analysis established a SUVmax cut-off value of 5.8 for discrimination between benign and malignant nodules (AUC: 0.748). Isthmus localization also remained significant in multivariate analysis (p=0.037). No other morphologic or ultrasonographic parameters were significant. In cases of focal FDG-avid TIs, an SUVmax value of ≥5.8 is associated with an increased risk of malignancy and may provide complementary information in risk stratification. However, SUVmax should be interpreted alongside clinical and ultrasonographic findings, not as a standalone decision-making tool.

BackgroundEarly treatment responses are important prognostic factors in childhood T-cell acute lymphoblastic leukemia (T-ALL) patients. The predictive values of early treatment responses in Chinese childhood T-ALL patients were still unknown.MethodsFrom January 2003 to December 2012, 74 consecutive patients aged ≤15 years with newly diagnosed T-ALL were treated with BCH-2003 protocol or CCLG-2008 protocol in the Department of Pediatric, Institute of Hematology and Blood Diseases Hospital in China. Predictive values of early treatment responses, including prednisone response, bone marrow morphology at day 15 and day 33 during induction chemotherapy, and minimal residual disease (MRD) monitored by flow cytometry after induction therapy (time point 1, TP1) and before consolidation therapy (time point 2, TP2), were analyzed.ResultsThe 5-year event free survival (EFS) and overall survival (OS) rates for these patients were 62.5 % (SE, 6.4) and 62.7 % (SE, 6.6), respectively. Prednisone poor responder was strongly associated with increased chance of induction failure (14.8 %) and decreased survival rate (5 year EFS rate, 51.1 % (SE, 10.5)). Patients with ≥25 % blast cells in bone marrow at day 15 were more likely to have an inferior outcome. 93.2 % of the T-ALL patients achieved complete remission at day 33 while patients with resistant disease all died of disease progression. MRD ≥10−2 at TP1 or MRD ≥10−3 at TP2 was significantly related to dismal prognosis. Risk groups classified by MRD at two time points could stratify patients into different groups: 29.0 % of the patients were MRD standard risk (MRD < 10−4 at both time points) with 3-year EFS rate of 100 %, 29.0 % were MRD high risk (MRD ≥10−2 at TP1 or MRD ≥10−2 at TP2) with 3-year EFS rate of 55.6 % (SE, 16.6) , and the rest of patients were defined as MRD intermediate risk with 3-year EFS rate of 85.7 % (SE, 13.2).ConclusionOur study demonstrated that MRD was the most powerful predictor of treatment outcome in childhood T-ALL patients and conventional morphological assessments of treatment response still played important roles in predicting treatment outcome and tailoring treatment intensity especially in countries with inadequate skills or financial resources for MRD monitoring.Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-015-0390-z) contains supplementary material, which is available to authorized users.

The goal of this prospective study was to compare the value of both conventional MRI and O-(2-18F-fluoroethyl)-L-tyrosine (FET) PET for response evaluation in glioblastoma patients treated with bevacizumab plus lomustine (BEV/LOM) at first progression. After chemoradiation with concomitant and adjuvant temozolomide, 21 IDH wild-type glioblastoma patients at first progression (age range, 33-75years; MGMT promoter unmethylated, 81%) were treated with BEV/LOM. Contrast-enhanced MRI and FET-PET scans were performed at baseline and after 8-10weeks. We obtained FET metabolic tumor volumes (MTV) and tumor/brain ratios. Threshold values of FET-PET parameters for treatment response were established by ROC analyses using the post-progression overall survival (OS) ≤/>9months as the reference. MRI response assessment was based on RANO criteria. The predictive ability of FET-PET thresholds and MRI changes on early response assessment was evaluated subsequently concerning OS using uni- and multivariate survival estimates. Early treatment response as assessed by RANO criteria was not predictive for an OS>9months (P = 0.203), whereas relative reductions of all FET-PET parameters significantly predicted an OS>9months (P < 0.05). The absolute MTV at follow-up enabled the most significant OS prediction (sensitivity, 85%; specificity, 88%; P = 0.001). Patients with an absolute MTV below 5ml at follow-up survived significantly longer (12 vs. 6months, P< 0.001), whereas early responders defined by RANO criteria lived only insignificantly longer (9 vs. 6months; P = 0.072). The absolute MTV at follow-up remained significant in the multivariate survival analysis (P = 0.006). FET-PET appears to be useful for identifying responders to BEV/LOM early after treatment initiation.

Background: Follicular lymphoma (FL) is the second most common NHL. It is generally associated with an indolent course, but a subgroup of patients has worse outcome, lower progression-free-survival (PFS) and higher risk of histological transformation (HT). Since Lugano classification, the Deauville criteria using the 5-point scale (D5PS) is validated as the interpretation method for response assessment PET scans in HL and NHL. Nevertheless, the prognostic value of D5PS in the interim evaluation in FL (PETINT) is not well stablished. Additionally, the quantitative value of SUVmax parameter in the response assessment is almost not studied. Aims: The aim of this study is to evaluate the prognostic value of PETINT evaluation and quantitative mid-induction SUVmax parameter in a cohort of FL patients followed and treated in a single, academic centre with chemo-immunotherapy. Methods: 179 consecutive FL patients were newly diagnosed between 2011 and 2020. 40 patients that did not require systemic treatment and 68 that did not have a PETINT evaluation were excluded. As well, patients with HT (9) and FL grade 3B (4) were excluded. From the 58 remaining patients, clinical, laboratory and PET examinations data was recorded. All patients were Ann-Arbor stage III-IV and were treated with chemo-immunotherapy. PET/CT examinations were acquired at baseline, mid-induction (after 4 cycles of treatment) and end of treatment (EOT). PET positive was considered when Deauville score (DS) was 4 or 5. Statistical analysis was performed with SPSS® using Cox regression, Kaplan-Meier survival curves and log-rank test. Results: The median age at diagnosis was 64 years (26-95) and 29 (50%) patients were female. 33/58 (57%) patients had a high risk FLIPI and 18/55 (33%) had a high risk PRIMA-PI. 37 (64%) patients were treated with R-CHOP and 21 with R-bendamustine. 44 (76%) patients received maintenance with rituximab. After a median follow-up of 43 months, 20 (34%) patients had progression. On PETINT, 19 (32%) patients were PET(+), and 10 of them remained PETEOT(+). Only one patient with PETINT(-), became PETEOT(+). PETINT(+) patients had a median PFS of 31 months compared with a median PFS of 88 months in PETINT(-) (p < 0.001), Figure 1. 38.2% PETINT(+) presented progression of disease in less than 24 months (POD24) vs 5.2% on those who were in PETINT(-), with a p<0.001. PETINT(-) presented a negative predictive value of 95%. No differences in OS was observed. 3/19 (16%) patients with PETINT(+) presented HT vs 1/39 (2%) with PETINT(-). Transformation-free survival was lower in patients with PETINT(+), with a trend towards significance (p= 0.057). Similar PFS results were obtained independently of prognostic index, treatment or maintenance received. Analysing the prognostic value of quantitative SUVmax, patients with SUVmax< 3,8 (28/58; 48%) presented better outcomes, with larger PFS (p < 0.001) and less HT (p= 0.004). Figure 2. Additionally, PET/CT findings at EOT were predictive of relapse, with a median PFS of 30 months in PETEOF (+) vs 88 months in PETEOT(-) (p = 0.005). PETEOT (+) presented a higher risk of HT (p= 0.004). Figure 3. Image:Summary/Conclusion: This study suggests that response assessment by PET at mid-induction is predictive of relapse in advanced stage FL patients treated with 1st line chemo-immunotherapy. With previous conflicting results, further studies are needed to confirm this preliminary data. Probably, new laboratory tests such as MRD monitored by liquid biopsy could improve the detection of this subgroup of high risk patients and help to develop a response-adapted precision therapy.