Quantitative analyses at baseline and interim PET evaluation for response assessment and outcome definition in patients with malignant pleural mesothelioma

Comparison of the role of 18 F-fluorodeoxyglucose PET/computed tomography and 68 Ga-labeled FAP inhibitor-04 PET/CT in patients with malignant mesothelioma

OBJECTIVE

In this study, we aimed to compare the role of 68 Ga-labeled FAP inhibitor ( 68 Ga-FAPI)-04 PET/computed tomography (CT) and 18 F-fluorodeoxyglucose ( 18 F-FDG) PET/CT in the evaluation of primary tumor and metastases in patients diagnosed with malignant mesothelioma.

MATERIALS AND METHODS

Our prospective study included 21 patients with histopathological diagnosis of malignant mesothelioma who underwent both 68 Ga-FAPI-04 PET/CT and 18 F-FDG PET/CT imaging between April 2022 and September 2022. Maximum standardized uptake value (SUVmax), metabolic tumor volume, total lesion glycolysis, tumor-to-background ratio (TBR) and highest SUVpeak (HPeak) values and lesion numbers were calculated from primary and metastatic lesions on FDG and FAPI PET/CT images. Findings obtained from FAPI and FDG PET/CT were compared.

RESULTS

More lesions were detected in 68 Ga-FAPI-04 PET/CT compared to 18 F-FDG PET/CT in primary tumor and lymph node metastases. Statistically significantly higher SUVmax and TBR values were found with FAPI PET/CT (primary lesion SUVmax and TBR, P  = 0.001 and P  < 0.001, respectively; lymph node SUVmax and TBR, P  = 0.016 and P  = 0.005, respectively). With FAPI PET/CT, upstage was observed according to tumor-node-metastasis staging in a total of seven patients including three patients with pleural origin, three patients with peritoneal origin and one patient with pericardial origin.

CONCLUSION

In addition to the stage change with 68 Ga-FAPI-04 PET/CT in malignant mesothelioma patients, a statistically significant superiority was observed in SUVmax, TBR and volumetric parameters in primary tumors and metastases.

Prognostic value of 18F-FDG PET/CT in malignant pleural mesothelioma: a meta-analysis

BACKGROUND

Several FDG PET/CT parameters have been utilized to evaluate the prognosis in malignant pleural mesothelioma (MPM). However, there are still controversial results due to the low incidence of MPM.

PURPOSE

To assess the prognostic value of 18F-FDG PET/CT in MPM.

MATERIAL AND METHODS

A systematic literature search was performed in PubMed, Embase, Medline, and The Cochrane Library to identify eligible studies from inception to 12 February 2020. The pooled hazard ratios (HRs) and 95% confidence intervals (CIs) of several variables, such as maximum standardized uptake value (SUV_max), the reduction of SUV_max after treatment (ΔSUV_max), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and the reduction of TLG after treatment (ΔTLG), were calculated. Meta-regression with subsequent subgroup analyses were conducted to determine the heterogeneity of cutoff values, treatment regimen, study design, uptake time, and scanners across various studies.

RESULTS

In total, 19 eligible studies including 1819 patients were enrolled in the meta-analysis. The univariate analysis showed that the pooled HRs (95% CI) of SUV_max, ΔSUV_max, MTV, TLG, and ΔTLG were 1.29 (1.16-1.42), 1.12 (1.05-1.19), 1.15 (1.00-1.33), 1.47 (1.23-1.76), and 1.27 (1.12-1.45), respectively. The multivariate analysis showed that the pooled HRs (95% CI) of SUV_max, ΔSUV_max, MTV, and TLG for overall survival (OS) were 1.20 (1.08-1.33), 1.10 (1.02-1.19), 0.95 (0.81-1.11), and 1.13 (1.08-1.18), respectively.

CONCLUSION

SUV_max, ΔSUV_max, TLG, and ΔTLG are significant prognostic indicators for OS, while more clinical studies are needed to confirm the prognostic value of MTV in MPM.

The efficacy of 18F-FDG PET/CT in monitoring disease progression in malignant pleural mesothelioma

OBJECTIVE

In the event of suspicion of malignant pleural mesothelioma (MPM) progression, imaging plays an important role. We aimed to evaluate the efficacy of ¹⁸F-FDG PET/CT in monitoring disease progression by comparing it with CT, and estimate median overall survival (OS) according to progression status with CT and ¹⁸F-FDG PET/CT.

MATERIALS AND METHODS

This was an observational, retrospective, single-institution study with MPM patients who had both ¹⁸F-FDG PET/CT and CT for monitoring disease progression from March 2009 to February 2020. Clinical features, radiological findings, and progression status according to CT [radiologic progression negative (RPN), radiologic progression positive (RPP)] and ¹⁸F-FDG PET/CT [metabolic progression negative (MPN), metabolic progression positive (MPP)] were recorded. The discrepancies and concordance between two methods were evaluated. The OS was estimated using the Kaplan-Meier method.

RESULTS

A total of 56 patients were included. There were thirty-one (55.3%) RPN and 25 (44.7%) RPP, while there were 26 (46.5%) MPN and 30 (53.5%) MPP. All RPP patients were also found to be MPP, however, among RPN, 5 patients (8.9% of all patients) were evaluated as MPP. The concordance between two methods in monitoring disease progression was very good (K = 0.423; p < 0.01). The OS was 26 ± 2.6 months in all patients. Kaplan-Meier curves between RPN and RPP, and between MPN and MPP did not show statistically significant differences (p = 0.56 and p = 0.25, respectively).

CONCLUSIONS

Both methods are equally acceptable in monitoring disease progression in MPM, even though ¹⁸F-FDG PET/CT detected more progression than CT did.

FDG PET/CT for Staging and Restaging Malignant Mesothelioma

Malignant mesothelioma is an aggressive tumor originating from the mesothelial cells and presenting in general with a very poor prognosis. The pleural localization represents the prevailing disease site, while peritoneal involvement is commonly rare. The WHO classifies mesotheliomas into epithelioid, biphasic, and sarcomatoid histotypes, having diverse outcome with the sarcomatoid or biphasic forms showing the poorest prognosis. Given the peculiar rind-like pattern of growth, mesothelioma assessment is rather challenging for medical imagers. Conventional imaging is principally based on contrast-enhanced CT, while the role of functional and metabolic imaging is regarded as complementary. By focusing essentially on the staging and restaging role of [18F]FDG PET/CT in malignant mesotheliomas, the present review will summarize the available data present in literature and provide some hints on alternative imaging and future perspectives. Given the prevailing incidence of pleural disease, the majority of the information will be addressed on malignant pleural mesothelioma, although a summary of principal characteristics and imaging findings in patients with peritoneal mesothelioma will be also provided.

A Role for PET/CT in response assessment of malignant pleural mesothelioma

Malignant pleural mesothelioma is a rare type of cancer, whose incidence, however, is increasing and will presumably continue to rise in the coming years. Key features of this disease comprise its mantle-shaped, pleura-associated, often multifocal growth, which cause diagnostic challenges. A growing number of mesotheliomas are being treated with novel immunotherapies for which no image derived general response criteria have been established. However, recent studies indicate that FDG-PET/CT could be superior for response assessment compared to CT-based criteria. This article aims at providing an overview of response assessment criteria dedicated to malignant pleural mesothelioma, such as mRECIST, iRECIST, and PERCIST. In addition, the potential future role of PET/CT in the management of malignant pleural mesothelioma will also be discussed.

The Prognostic Value of 18F-FDG PET Imaging at Staging in Patients with Malignant Pleural Mesothelioma: A Literature Review

Malignant pleural mesothelioma (MPM) is an aggressive malignancy, frequently diagnosed at locally-advanced/metastatic stages. Due to a very poor prognosis and limited treatment options, the need to identify new prognostic markers represents a great clinical challenge. The prognostic role of metabolic information derived from Positron Emission Tomography (PET) with ¹⁸F-Fluoro-deoxy-glucose (¹⁸F-FDG) has been investigated in different MPM settings, however with no definitive consensus. In this comprehensive review, the prognostic value of FDG-PET imaging exclusively performed at staging in MPM patients was evaluated, conducting a literature search on PubMed/MEDLINE from 2010 to 2020. From the 19 selected studies, despite heterogeneity in several aspects, staging FDG-PET imaging emerges as a valuable prognostic biomarker, with higher tumor uptake predictive of worse prognosis, and with volumetric metabolic parameters like Metabolic Tumor Volume, (MTV) and Total Lesion Glycolisis (TLG) performing better than SUVmax. However, PET uptake parameters were not always confirmed as independent prognostic factors, especially in patients previously treated with pleurodesis and with a non-epithelioid histotype. Future prospective studies in larger and clinically homogeneous populations, and using more standardized methods of PET images analysis, are needed to further validate the value of staging FDG-PET in the prognostic MPM stratification, with a potential impact on better patient-tailored treatment planning, in the perspective of personalized medicine.

Histology of the pleural rind at [18F]FDG PET/CT hot and cold spots in mesothelioma patients after talc pleurodesis and neoadjuvant chemotherapy

The role of 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography/computed tomography ([¹⁸F]FDG PET/CT) in evaluating induction chemotherapy in pleural mesothelioma (PM) patients is debated. We compared histology at tumor sites with high versus low [¹⁸F]FDG uptake in order to define a morphologic correlate for persistent metabolic activity. Twenty PM patients with talc pleurodesis and induction chemotherapy followed by extrapleural pleuro-pneumonectomy (EPP, n = 17) or tumor debulking (n = 3) were included. All patients received a PET/CT scan prior to surgery. Orthogonal tissue sections of pleural rind (n total=86) were taken at areas of maximum standardized uptake value (SUV_max, n = 53) and of low [¹⁸F]FDG uptake (n = 33) and scored on hematoxylin-eosin and immunohistochemical stainings. Total metabolic activity was scored semiquantitatively. Mean SUV_max of hot and cold spots correlated with total metabolic activity per patient, but no correlation was found with ypT and tumor cells were present in both hot and cold areas. SUV_max of only hot spots and cold versus hot spots as well as cold versus hot patients correlated with increased thickness of total pleural rind and fibrosis reaction, but not thickness of vital tumor cells or giant cell reaction. They further correlated with increased expression of glucose transporter 1 (GLUT1) in giant cells but not mesothelioma amount, density, vitality or vascularization. Biphasic histology was associated with SUV_max in only hot spots and higher total metabolic activity (all p-values <0.05). Interpretation of [¹⁸F]FDG PET/CT in PM patients is difficult after talc pleurodesis and induction chemotherapy. High glucose turnover is mostly related to fibro-inflammatory remodeling of the pleural rind and GLUT1 transporter expression in giant cells. Response assessment using this technology should only be done to assess extra-thoracic lesions.

Is 18F-FDG PET/CT capable of differential diagnosis from tuberculous pleurisy from malignant mesothelioma?

AIM

18F-Fluorodeoxyglucose (FDG) PET/computerized tomography (CT) is a valuable method in the diagnosis of malignant pleural mesothelioma (MPM). But, some infections, particularly tuberculosis, are known to mimic cancer. We aimed to compare the FDG PET/CT findings of tuberculosis pleurisy (TP) and malignant mesothelioma and evaluate its role of differential diagnosis.

MATERIAL AND METHOD

We retrospectively reviewed the data from 85 patients (45 patients with MPM and 40 patients with TP) who underwent FDG PET/CT. All images were reevaluated and pleural thickening, maximum standardized uptake values (SUVmax), lymphatic uptake and accompanying parenchymal findings were noted.

RESULTS

There was no significant difference in age and sex between the two groups. Pleural thickening was more prominent in the MPM group. Mean pleural thickness was 21.4 ± 18.6 mm in the MPM group and 6.8 ± 3.5 mm in the TP group (P = 0.0). Besides pleural pathology, lymph nodes involvement in the thoracic (P = 0.0) and extrathoracic area (P = 0.34) and parenchymal findings were prominent in the TP group (P = 0.0). However, there was no significant difference in pleural SUVmax values between the two groups (P = 0.61).

CONCLUSION

Intense pleural FDG uptake can be observed in TP like malignant mesothelioma. For the evaluation of the pleural pathologies in the tuberculosis endemic countries, it should be considered that FDG PET/CT may have false-positive results. Evaluation of increased pleural FDG uptake together with the detected parenchymal findings and lymphatic involvement may help us to make more accurate interpretation of the diagnosis.

"PET/CT Variants and Pitfalls in Lung Cancer and Mesothelioma"

2-deoxy-2-[¹⁸F]fluoro-D-glucose [¹⁸F]FDG-PET/CT represents the metabolic imaging of choice in various cancer types. Used either at diagnosis or during treatment response assessment, the modality allows for a more accurate definition of tumor extent compared to morphological imaging and is able to predict the therapeutic benefit earlier in time. Due to the aspecific uptake property of [¹⁸F]FDG there is an overlap of its distribution in normal and pathological conditions, which can make the interpretation of the imaging challenging. Lung and pleural neoplasia are no exception to this, thus acknowledging of possible pitfalls and artifacts are mandatory for image interpretation. While most pitfalls and artifacts are common for all indications with metabolic imaging with [¹⁸F]FDG-PET/CT, there are specific variants and pitfalls in lung cancer and malignant pleural mesothelioma. The aim of the present article is to shed light on the most frequent and relevant variants and pitfalls in [¹⁸F]FDG-PET/CT imaging in lung cancer and malignant pleural mesothelioma.

PET/CT-Based Response Evaluation in Cancer-a Systematic Review of Design Issues

Positron emission tomography/x-ray computed tomography (PET/CT) has long been discussed as a promising modality for response evaluation in cancer. When designing respective clinical trials, several design issues have to be addressed, especially the number/timing of PET/CT scans, the approach for quantifying metabolic activity, and the final translation of measurements into a rule. It is unclear how well these issues have been tackled in quest of an optimised use of PET/CT in response evaluation. Medline via Ovid and Science Citation Index via Web of Science were systematically searched for articles from 2015 on cancer patients scanned with PET/CT before and during/after treatment. Reports were categorised as being either developmental or evaluative, i.e. focusing on either the establishment or the evaluation of a rule discriminating responders from non-responders. Of 124 included papers, 112 (90 %) were accuracy and/or prognostic studies; the remainder were response-curve studies. No randomised controlled trials were found. Most studies were prospective (62 %) and from single centres (85 %); median number of patients was 38.5 (range 5-354). Most (69 %) of the studies employed only one post-baseline scan. Quantification was mainly based on SUVmax (91 %), while change over time was most frequently used to combine measurements into a rule (79 %). Half of the reports were categorised as developmental, the other half evaluative. Most development studies assessed only one element (35/62, 56 %), most frequently the choice of cut-off points (25/62, 40 %). In summary, the majority of studies did not address the essential open issues in establishing PET/CT for response evaluation. Reasonably sized multicentre studies are needed to systematically compare the many different options when using PET/CT for response evaluation.

Exceptional Regression of Malignant Pleural Mesothelioma with Pembrolizumab Monotherapy

The lead author with clinical stage I malignant pleural mesothelioma, epithelioid type, highly programmed cell death ligand 1 (PD-L1) positive, and BAP1 negative, experienced a prompt and exceptionally favorable response to pembrolizumab monotherapy. After cessation of treatment due to immune-related endocrinopathies, complete metabolic response on interim PET/CT scan was achieved. Two years after initial diagnosis, unifocal tumor reactivation was addressed with successful pembrolizumab monotherapy rechallenge. Immunotherapy, typically not used as frontline treatment for malignant pleural mesothelioma, may provide an effective and durable response for some patients. Based on this single case study, epithelioid type tumors with strongly positive PD-L1 and BAP1-negative immunohistochemical markers may be well suited for treatment with immune checkpoint inhibitors such as pembrolizumab.

Predicting tumor response and outcome of second-look surgery with 18F-FDG PET/CT: insights from the GINECO CHIVA phase II trial of neoadjuvant chemotherapy plus nintedanib in stage IIIc-IV FIGO ovarian cancer

Background

This ancillary study aimed to evaluate ¹⁸F-FDG PET parameter changes after one cycle of treatment compared to baseline in patients receiving first-line neoadjuvant anti-angiogenic nintedanib combined to paclitaxel-carboplatin chemotherapy or chemotherapy plus placebo and to evaluate the ability of ¹⁸F-FDG PET parameters to predict progression-free survival (PFS), overall survival (OS), and success of second-look surgery.

Materials and methods

Central review was performed by two readers blinded to the received treatment and to the patients’ outcome, in consensus, by computing percentage change in PET metrics within a volume of interest encompassing the entire tumor burden. EORTC and PERCIST criteria were applied to classify patients as responders (partial metabolic response and complete metabolic response) or non-responders (stable metabolic disease and progressive metabolic disease). Also analyzed was the percentage change in metabolic active tumor volume (MATV) and total lesion glycolysis (TLG).

Results

Twenty-four patients were included in this ancillary study: 10 received chemotherapy + placebo and 14 chemotherapy + nintedanib. PERCIST and EORTC criteria showed similar discriminative power in predicting PSF and OS. Variation in MATV/TLG did not predict PFS or OS, and no optimal threshold could be found for MATV/TLG for predicting survival. Complete cytoreductive surgery (no residual disease versus residual disease < 0.25 cm/0.25–2.5 cm/> 2.5 cm) was more frequent in responders versus non-responders (P = 0.002 for PERCIST and P = 0.02 for EORTC criteria). No correlation was observed between the variation of PET data and the variation of CA-125 blood level between baseline sample and that performed contemporary to the interim PET, but a statistically significant correlation was observed between ΔSUL_peak and ΔCA-125 between baseline sample and that performed after the second cycle.

Conclusion

¹⁸F-FDG PET using EORTC or PERCIST criteria appeared to be a useful tool in ovarian cancer trials to analyze early tumor response, and predict second-look surgery outcome and survival. An advantage of PERCIST is the correlation of ΔSUL_peak and ΔCA-125, PET response preceding tumor markers response by 1 month. Neither MATV nor TLG was useful in predicting survival.

Trial registration

NCT01583322 ARCAGY/ GINECO GROUP GINECO-OV119, 24 April 2012

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-020-05092-3.

Volumetric PET Response Assessment Outperforms Conventional Criteria in Patients Receiving High-Dose Pembrolizumab for Malignant Mesothelioma

Fixed-dose pembrolizumab (200 mg absolute, day 1, every 3 wk) for the treatment of malignant pleural mesothelioma did not result in survival benefit in the phase 3 PROMISE-meso trial compared with second-line chemotherapy. Because of lack of validated imaging response criteria, responder subgroups with potential survival benefit have not yet been identified. Here, we administered high-dose pembrolizumab (10 mg/kg, day 1, every 2 wk) considering the KEYNOTE-028 trial and assessed the prognostic value of PET metabolic response in patients with chemotherapy-resistant malignant mesothelioma of the pleura or peritoneum. Methods: Data from 27 patients with baseline and follow-up ¹⁸F-FDG PET/CT imaging were retrospectively analyzed. RECIST, version 1.1; modified RECIST; and PERCIST using both tumor lesion metabolic activity in a 1 cm³ spheric region of interest of up to 5 target lesions (PERCIST_SULpeak) and metabolic tumor volume PERCIST (PERCIST_MTV) were applied separately to categorize responders in CT and PET imaging studies. Progression-free survival (PFS) and overall survival (OS) were compared between responders and nonresponders using Kaplan-Meier and log-rank analyses. Programmed cell death protein 1 ligand expression status was assessed, and its association with outcome was investigated. Results: Twenty-seven patients had ¹⁸F-FDG PET/CT imaging at baseline and after at least 4 cycles pembrolizumab. Median PFS and OS were 3.4 and 15.1 mo, respectively. Response rates were 7%, 7%, 30%, and 30% based on RECIST, modified RECIST, PERCIST_SULpeak, and PERCIST_MTV response criteria, respectively. Response according to PERCIST_MTV predicted prolonged OS or PFS (P < 0.01), whereas all other imaging criteria and programmed cell death protein 1 ligand expression did not. Conclusion: ¹⁸F-FDG PET metabolic volume response predicts survival in patients with malignant mesothelioma receiving high-dose pembrolizumab. These results should prompt inclusion of PET response assessment in future phase 3 clinical trials.

Comparison of modified Response Evaluation Criteria in Solid Tumors, European Organization for Research and Treatment of Cancer criteria, and PET Response Criteria in Solid Tumors for evaluation of tumor response to chemotherapy and prognosis prediction in patients with unresectable malignant pleural mesothelioma

OBJECTIVE

To compare modified RECIST (mRECIST), EORTC criteria, and PERCIST for response evaluation and prognosis prediction in advanced malignant pleural mesothelioma (MPM) patients treated with chemotherapy.

METHODS

Patients with MPM and not curative surgery candidates (n = 75) underwent standard chemotherapy with cisplatin and pemetrexed. CT and [F]fluorodeoxyglucose PET/CT scans were performed at baseline and after three chemotherapy cycles. Chemotherapeutic response was evaluated according to mRECIST, EORTC, and PERCIST, then concordance among those was assessed using Cohen's κ coefficient. PFS and OS were examined using log-rank and Cox methods.

RESULTS

With EORTC, 27 patients had PMD, 23 SMD, 17 PMR, and eight CMR, while with PERCIST those were 28, 22, 11, and 14, respectively. Using mRECIST, 28 had PD, 29 SD, 18 PR, and 0 CR. Although there was high concordance between EORTC and PERCIST (82.7% of patients; κ = 0.83), that between mRECIST and EORTC (38.7%; κ = 0.27) and mRECIST and PERCIST (36.0%; κ = 0.26) was low. According to both EORTC and PERCIST, patients with no progression (CMR/PMR/SMD) showed significantly longer PFS and OS than PMD patients (EORTC: P = 0.0024 and P = 0.039, respectively, PERCIST: P = 0.0012 and P = 0.024, respectively), while according to mRECIST, those who achieved no progression (PR/SD) showed significantly longer PFS than PD patients (P = 0.011), but not significantly longer OS (P = 0.11).

CONCLUSION

EORTC and PERCIST are more accurate than mRECIST for evaluation of tumor response to chemotherapy and predicting prognosis in unresectable MPM patients.

18F-FDG PET Assessment of Malignant Pleural Mesothelioma: Total Lesion Volume and Total Lesion Glycolysis-The Central Role of Volume

Cancer survival is related to tumor volume. ¹⁸F-FDG PET measurement of tumor volume holds promise but is not yet a clinical tool. Measurements come in 2 forms: the first is total lesion volume (TLV) based on the number of voxels in the tumor, and the second is total lesion glycolysis (TLG), which is the TLV multiplied by the average SUL (i.e., SUV normalized for lean mass) of the tumor (SUL_average). In this study, we measured tumor volume in patients with malignant pleural mesothelioma (MPM). Methods: A threshold-based program in Interactive Data Language was developed to measure tumor volume in ¹⁸F-FDG PET images. Nineteen patients with MPM were studied before and after 2 cycles (6 wk) of chemoimmunotherapy. Measurements included TLV, TLG, the sum of the SULs in the tumor (SUL_total, a measure of total ¹⁸F-FDG uptake), and SUL_average Results: Baseline TLV ranged from 11 to 2,610 cm³ TLG ranged from 32 to 8,552 cm³ g/mL and correlated strongly with TLV. Although tumor volumes ranged over 3 orders of magnitude, SUL_average stayed within a narrow range of 2.4-5.3 units. Thus, TLV was the major component of TLG, whereas SUL_average was a minor component and was essentially constant. Further evaluation of SUL_average showed that in this cohort its 2 components, SUL_total and TLV, changed in parallel and were strongly correlated (r = 0.99, P < 0.01). Thus, whether the tumors were large or small, ¹⁸F-FDG uptake as measured by SUL_total was proportional to the TLV. Conclusion: TLG equals TLV multiplied by SUL_average, essentially TLV multiplied by a constant. Thus TLG, commonly considered a measure of metabolic activity in tumors, is also in this cohort a measure of tumor volume. The constancy of SUL_average is due to the fact that ¹⁸F-FDG uptake is proportional to tumor volume. Thus, in this study, ¹⁸F-FDG uptake was also a measure of volume.

Prognostic value of SUVmax on 18F-fluorodeoxyglucose PET/CT scan in patients with malignant pleural mesothelioma

Introduction

The maximum standardized uptake value (SUVmax) in ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) may be of prognostic significance for patients with malignant pleural mesothelioma (MPM). This retrospective study aimed to investigate the prognostic value of the SUVmax in patients with MPM.

Materials and methods

Medical records were retrospectively reviewed for the patients who were diagnosed with histopathologically proven MPM between 2009 and 2018 at Samsung Medical Center. For each patient, SUVmax was calculated for the primary lesion on PET/CT. To determine optimal cutoff values for predicting mortality, receiver operating characteristic curves were used.

Results

Among the 54 study patients, 34 (63.0%) had epithelioid subtype, 13 (24.1%) had sarcomatoid or biphasic subtype, and 7 (13.0%) had mesothelioma, not otherwise specified (NOS). The median overall survival (OS) was 8.7 months, and the median SUVmax was 9.9. The median values of SUVmax were 5.5 in patients with epithelioid subtype, 11.7 in those with sarcomatoid/biphasic subtype, and 13.3 in those with NOS subtype (P = 0.003). The optimal cutoff values of SUVmax to predict mortality were 10.1 in all patients, and 8.5 in patients with epithelioid subtype. In multivariate analysis, SUVmax was significantly associated with overall survival in all patients (P = 0.003) and in patients with epithelioid subtype (P = 0.012), but not in those with non-epithelioid subtype.

Conclusions

SUVmax in PET/CT is an independent prognostic factor in patients with MPM, especially those with epithelioid subtype. The histologic subtype of MPM should be considered when evaluating the prognostic significance of SUVmax.

Radiologic Considerations and Standardization of Malignant Pleural Mesothelioma Imaging Within Clinical Trials: Consensus Statement from the NCI Thoracic Malignancy Steering Committee - International Association for the Study of Lung Cancer - Mesothelioma Applied Research Foundation Clinical Trials Planning Meeting

Detailed guidelines pertaining to radiological assessment of malignant pleural mesothelioma are currently lacking due to the rarity of the disease, complex morphology, propensity to invade multiple planes simultaneously, and lack of specific recommendations within the radiology community about assessment, reporting, and follow-up. In March 2017, a multidisciplinary meeting of mesothelioma experts was co-sponsored by the National Cancer Institute Thoracic Malignancy Steering Committee, International Association for the Study of Lung Cancer, and the Mesothelioma Applied Research Foundation. One of the outcomes of this conference was the foundation of detailed, multidisciplinary consensus imaging and management guidelines. Here, we present the recommendations for radiologic assessment of malignant pleural mesothelioma in the setting of clinical trial enrollment. We discuss optimization of imaging parameters across modalities, standardized reporting, and response assessment within clinical trials.

Prognostic and predictive role of [18 F]fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with unresectable malignant pleural mesothelioma (MPM) treated with up-front pemetrexed-based chemotherapy

The aim of this study was to evaluate the role of metabolic parameters analyzed at baseline and at interim FDG‐PET in predicting disease outcome in unresectable MPM patients receiving pemetrexed‐based chemotherapy. A consecutive series of MPM patients treated between February 2004 and July 2013 with first‐line pemetrexed‐based chemotherapy, and evaluated by FDG‐PET and CT scan at baseline and after two cycles of chemotherapy, was reviewed. Best CT scan response was assessed according to modified RECIST criteria. Progression‐free survival (PFS) and overall survival (OS) were correlated with FDG‐PET parameters, such as maximum standardized uptake value (SUV_max), total lesion glycolysis (TLG), and percentage changes in SUV_max (∆SUV) and TLG (∆TLG). Overall, 142 patients were enrolled; 77 (54%) received talc pleurodesis before chemotherapy. Baseline SUV_max and TLG showed a statistically significant correlation with PFS and OS (P < 0.05) in both group of patients (treated and untreated with pleurodesis). In 65 patients not receiving pleurodesis, SUV_max reduction ≥25% (∆SUV ≥ 25%) and TLG reduction ≥30% (∆TLG ≥ 30%) were significantly associated with longer PFS (P < 0.05). Patients showing both ∆SUV ≥ 25% and ∆TLG ≥ 30% responses had a significant reduction in the risk of disease progression (HR:0.31, P < 0.001) and death (HR:0.52, P = 0.044). Neither ∆SUV nor ∆TLG showed similar association with survival outcomes in patients treated with pleurodesis. Our study confirmed the prognostic role of baseline FDG‐PET in a large series of MPM patients treated with first‐line pemetrexed‐based chemotherapy. Moreover, use of ∆SUV ≥ 25% and ∆TLG ≥ 30% as cut‐off values to define early metabolic response supported the role of FDG‐PET in predicting disease outcome and treatment response in patients not receiving pleurodesis.

State-of-the-art: Radiological investigation of pleural disease

Pleural disease is common. Radiological investigation of pleural effusion, thickening, masses, and pneumothorax is key in diagnosing and determining management. Conventional chest radiograph (CXR) remains as the initial investigation of choice for patients with suspected pleural disease. When abnormalities are detected, thoracic ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) can each play important roles in further investigation, but appropriate modality selection is critical. US adds significant value in the identification of pleural fluid and pleural nodularity, guiding pleural procedures and, increasingly, as "point of care" assessment for pneumothorax, but is highly operator dependent. CT scan is the modality of choice for further assessment of pleural disease: Characterising pleural thickening, some pleural effusions and demonstration of homogeneity of pleural masses and areas of fatty attenuation or calcification. MRI has specific utility for soft tissue abnormalities and may have a role for younger patients requiring follow-up serial imaging. MRI and PET/CT may provide additional information in malignant pleural disease regarding prognosis and response to therapy. This article summarises existing techniques, highlighting the benefits and applications of these different imaging modalities and provides an up to date review of the evidence.

Value of volume-based early metabolic response in patients with unresectable thymic epithelial tumor

OBJECTIVE

We conducted this study to investigate the value of early metabolic responses assessed by (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) in predicting prognosis and monitoring treatment response in patients with unresectable thymic epithelial tumors (TETs).

PATIENTS AND METHODS

Study subjects were selected from the prospective dataset of a phase II clinical trial for cisplatin plus Cremorphor EL-free paclitaxel. A total of thirty patients with unresectable TETs who underwent baseline and early post treatment scan after two cycles of chemotherapy were enrolled (22 Male; mean age 55.0±15.0years). Metabolic parameters including metabolic tumor volume (MTV) and total lesion glycolysis (TLG) of the tumor lesions were measured.

RESULTS

Multivariate analysis using Cox proportional hazards regression model showed that percent decrease of MTV (HR=0.995 by 1% decrease, P=0.037) and TLG (HR=0.996 by 1% decrease, P=0.044) were significant predictors of progression-free survival (PFS). Receiver operating characteristic curve identified an 88.0% decrease in MTV and a 92.0% decrease in TLG as the optimal cut-off value for disease progression. Responders with ≥88% of ΔMTV and ≥92% of Δ TLG had significantly longer PFS than non-responders (P=0.012, 0.026, respectively).

CONCLUSION

The percent decrease in MTV and TLG of tumor lesions measured by early post treatment FDG PET/CT significantly associated with disease progression in this study. Early metabolic response based on these volumetric parameters has the potential to monitor treatment response and predict prognosis in patients with unresectable TETs.

The potential value of volume-based quantitative PET parameters and increased bone marrow uptake for the prediction of survival in patients with malignant pleural mesothelioma

PURPOSE

The aim of this study was to investigate the relationship between volume-based quantitative PET parameters and survival in patients with malignant pleural mesothelioma (MPM) and to evaluate the potential value of bone marrow (BM) uptake in predicting prognosis.

MATERIALS AND METHODS

We retrospectively reviewed the data of 51 patients with MPM who underwent initial staging by fluorine-18-fluorodeoxyglucose (F-FDG) PET/computerized tomography (PET/CT). F-FDG-PET images were visually and quantitatively re-evaluated and maximum standardized uptake values (SUVmax), mean standardized uptake values (SUVmean), metabolic tumor volume (MTV), total lesion glycolysis of primary tumors, and pleural thickening were calculated. In addition, BM and liver uptakes were measured; also, the degree of BM uptake was scored visually. BM/liver ratio and visual BM uptake score were noted. The correlations between quantitative PET parameters, BM uptake, and overall survival were analyzed.

RESULTS

F-FDG-PET scans upstaged 6 (11.8%) of 51 patients because of detection of previously unknown distant metastasis. On univariate analysis, advanced disease stage, high leukocyte count (≥10×10/ml), pleural thickening greater than 13 mm, SUVmax, SUVmean, MTV, total lesion glycolysis, BM/liver greater than 1.01, and visual score 1 and 2 were negative prognostic factors (P<0.05). In multivariate analysis, SUVmax greater than 8.6 [P=0.027, hazard ratio (HR): 2.961], MTV greater than 112 (P=0.001, HR: 4.861), and visual score 2 (P=0.035, HR: 3.827) were associated independently with a poor prognosis.

CONCLUSION

The presence of distant metastasis is more predictive of survival than PET nodal status in MPM patients. PET/CT has the potential to provide prognostic information in MPM patients and there was a good correlation between overall survival and volume-based PET parameters. Determination of BM uptake may contribute toward the prediction of patient outcome with other quantitative PET parameters.

Present and future roles of FDG-PET/CT imaging in the management of malignant pleural mesothelioma

Positron emission tomography/computed tomography (PET/CT) integrated with 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)F-FDG) has emerged as a powerful tool for combined metabolic and anatomic evaluations in clinical oncologic imaging. This review discusses the utility of (18)F-FDG PET/CT as a tool to manage patients with malignant pleural mesothelioma. We discuss different stages of patient management in malignant pleural mesothelioma, including diagnosis, initial staging, therapy planning, early treatment response assessment, re-staging, and prognosis.

Malignant pleural mesothelioma: initial experience in integrated (18)F-FDG PET/MR imaging

PURPOSE

This study aims to compare staging results of (18)F-FDG PET/computed tomography (CT) and integrated PET/magnetic resonance (MR) in malignant pleural mesothelioma (MPM) patients and to investigate a potential apparent diffusion coefficient (ADC)/SUV correlation.

MATERIALS AND METHODS

Six patients with MPM underwent (18)F-FDG PET/CT and PET/MR including diffusion-weighted imaging. Thoracic TNM staging was performed for both modalities. SUV and ADC were assessed in therapy-naive pleural lesions.

RESULTS

In thoracic TNM staging, no differences were found between PET/CT and PET/MR. An inverse correlation was observed between SUVmean and ADCmin (r=-0.63, P=.002).

CONCLUSION

MPM can be staged using PET/MR. The inverse correlation ADC/SUV indicates that future research on multiparametric therapy response evaluation may be warranted.