Review on radiomic analysis in 18F-fluorodeoxyglucose positron emission tomography for prediction of melanoma outcomes.

Over the past decade, several strategies have revolutionized the clinical management of patients with cutaneous melanoma (CM), including immunotherapy and targeted tyrosine kinase inhibitor (TKI)-based therapies. Indeed, immune checkpoint inhibitors (ICIs), alone or in combination, represent the standard of care for patients with advanced disease without an actionable mutation. Notably BRAF combined with MEK inhibitors represent the therapeutic standard for disease disclosing BRAF mutation. At the same time, FDG PET/CT has become part of the routine staging and evaluation of patients with cutaneous melanoma. There is growing interest in using FDG PET/CT measurements to predict response to ICI therapy and/or target therapy. While semiquantitative values such as standardized uptake value (SUV) are limited for predicting outcome, new measures including tumor metabolic volume, total lesion glycolysis and radiomics seem promising as potential imaging biomarkers for nuclear medicine. The aim of this review, prepared by an interdisciplinary group of experts, is to take stock of the current literature on radiomics approaches that could improve outcomes in CM.

Clinical application of a population-based input function (PBIF) for a shortened dynamic whole-body FDG-PET/CT protocol in patients with metastatic melanoma treated by immunotherapy.

BACKGROUND: The aim was to investigate the feasibility of a shortened dynamic whole-body (dWB) FDG-PET/CT protocol and Patlak imaging using a population-based input function (PBIF), instead of an image-derived input function (IDIF) across the 60-min post-injection period, and study its effect on the FDG influx rate (Ki) quantification in patients with metastatic melanoma (MM) undergoing immunotherapy. METHODS: Thirty-seven patients were enrolled, including a PBIF modeling group (n = 17) and an independent validation cohort (n = 20) of MM from the ongoing prospective IMMUNOPET2 trial. All dWB-PET data were acquired on Vision 600 PET/CT systems. The PBIF was fitted using a Feng's 4-compartments model and scaled to the individual IDIF tail's section within the shortened acquisition time. The area under the curve (AUC) of PBIFs was compared to respective IDIFs AUC within 9 shortened time windows (TW) in terms of linear correlation (R2) and Bland-Altman tests. Ki metrics calculated with PBIF vs IDIF on 8 organs with physiological tracer uptake, 44 tumoral lesions of MM and 11 immune-induced inflammatory sites of pseudo-progression disease were also compared (Mann-Whitney test). RESULTS: The mean ± SD relative AUC bias was calculated at 0.5 ± 3.8% (R2 = 0.961, AUCPBIF = 1.007 × AUCIDIF). In terms of optimal use in routine practice and statistical results, the 5th-7th pass (R2 = 0.999 for both Ki mean and Ki max) and 5th-8th pass (mean ± SD bias = - 4.9 ± 6.5% for Ki mean and - 4.8% ± 5.6% for Ki max) windows were selected. There was no significant difference in Ki values from PBIF5_7 vs IDIF5_7 for physiological uptakes (p > 0.05) as well as for tumor lesions (mean ± SD Ki IDIF5_7 3.07 ± 3.27 vs Ki PBIF5_7 2.86 ± 2.96 100ml/ml/min, p = 0.586) and for inflammatory sites (mean ± SD Ki IDIF5_7 1.13 ± 0.59 vs Ki PBIF5_7 1.13 ± 0.55 100ml/ml/min, p = 0.98). CONCLUSION: Our study showed the feasibility of a shortened dWB-PET imaging protocol with a PBIF approach, allowing to reduce acquisition duration from 70 to 20 min with reasonable bias. These findings open perspectives for its clinical use in routine practice such as treatment response assessment in oncology.

Characteristics and treatment options of glucagonomas: a national study from the French Group of Endocrine Tumors and ENDOCAN-RENATEN network.

OBJECTIVE: Glucagonoma is a very rare functional pancreatic neuroendocrine tumor (PanNET). We aimed to provide data on the diagnosis, prognosis, and management of patients with glucagonoma. DESIGN AND METHODS: In this retrospective national cohort, we included all patients with glucagonoma, defined by at least 1 major criterion (necrolytic migratory erythema [NME] and/or recent-onset diabetes, and/or weight loss ≥ 5 kg) associated with either glucagonemia > 2 × upper limit of normal or positive glucagon immunostaining. Antisecretory efficacy was defined as partial/complete resolution of glucagonoma symptoms. Antitumor efficacy was assessed according to the time to next treatment (TTNT). RESULTS: Thirty-eight patients were included with median age 58.7 yo, primary PanNET located in the tail (68.4%), synchronous metastases (63.2%). Median Ki-67 index was 3%. Most frequent glucagonoma symptoms at diagnosis were NME (86.8%), weight loss (68.4%), and diabetes (50%). Surgery of the primary PanNET was performed in 76.3% of cases, mainly with curative intent (61.5%). After surgery, complete resolution of NME was seen in 93.8% (n = 15/16). The secretory response rates were 85.7%, 85.7%, 75%, and 60% with surgery of metastases (n = 6/7), chemotherapy (n = 6/7), liver-directed therapy (n = 6/8), and somatostatin analogs (n = 6/10), respectively. All lines combined, longer TTNT was reported with chemotherapy (20.2 months). Median overall survival (OS) was 17.3 years. The Ki-67 index > 3% was associated with shorter OS (hazard ratio 5.27, 95% CI [1.11-24.96], P = .036). CONCLUSION: Patients with glucagonoma had prolonged survival, even in the presence of metastases at diagnosis. Curative-intent surgery should always be considered. Chemotherapy, peptide receptor radionuclide therapy, or liver-directed therapy seems to provide both substantial antitumor and antisecretory efficacies.

Case Report: Long-term metabolic response of metastatic uveal melanoma to pembrolizumab on FDG-PET/CT despite a serial pseudoprogressions phenomenon.

Uveal melanoma (UV) is a rare and aggressive melanoma with poor 1-year survival. up to 50% of UV patients develop metastases, mainly to the liver. Here, the authors present a 2-deoxy-2-[18F] fluoro-D-glucose positron emission tomography (18F-FDG-PET) study of a very rare case of secondarily metastatic UV in an 81-year-old Caucasian with a dramatic response to pembrolizumab associated with serial pseudogression. 18F-FDG-PET associated with clinical status and peripheral blood derived neutrophil-to-lymphocyte ratio (dNLR) were performed to guide therapeutic strategy due to an atypical pseudoprogression phenomenon.

Genetic testing in prolactinomas: a cohort study.

BACKGROUND: Prolactinomas represent 46%-66% of pituitary adenomas, but the prevalence of germline mutations is largely unknown. We present here the first study focusing on hereditary predisposition to prolactinoma. OBJECTIVE: We studied the prevalence of germline mutations in a large cohort of patients with isolated prolactinomas. MATERIALS AND METHODS: A retrospective study was performed combining genetic and clinical data from patients referred for genetic testing of MEN1, AIP, and CDKN1B between 2003 and 2020. SF3B1 was Sanger sequenced in genetically negative patients. RESULTS: About 506 patients with a prolactinoma were included: 80 with microprolactinoma (15.9%), 378 with macroprolactinoma (74.7%), 48 unknown; 49/506 in a familial context (9.7%). Among these, 14 (2.8%) had a (likely) pathogenic variant (LPV) in MEN1 or AIP, and none in CDKN1B. All positive patients had developed a macroprolactinoma before age 30. The prevalence of germline mutations in patients with isolated macroprolactinoma under 30 was 4% (11/258) in a sporadic context and 15% (3/20) in a familial context. Prevalence in sporadic cases younger than 18 was 15% in men (5/33) and 7% in women (4/57). No R625H SF3B1 germline mutation was identified in 264 patients with macroprolactinomas. CONCLUSIONS: We did not identify any LPVs in patients over 30 years of age, either in a familial or in a sporadic context, and in a sporadic context in our series or the literature. Special attention should be paid to young patients and to familial context.

Risk factors for hypothyroidism following hemithyroidectomy.

OBJECTIVE: Hypothyroidism is the most common complication of hemithyroidectomy for thyroid nodules. This retrospective cohort study investigated the prognostic factors for hypothyroidism following hemithyroidectomy. METHODS: We included patients who underwent hemithyroidectomy between 2016 and 2017, excluding those with history of preoperative hypothyroidism or malignancy on histopathological examination. The primary endpoint was development of hypothyroidism during follow-up (TSH≥2 above normal). RESULTS: Twenty-six of the 128 included patients (20%) developed postoperative hypothyroidism. The following independent prognostic factors were found: preoperative TSH level>1.5 mIU/L (OR 2.11; P=0.013), and remaining thyroid volume adjusted for body surface area<4.0mL/m2 (OR 1.77; P=0.015). Twenty-one patients (81%) had first TSH values above the upper limit of normal. Postoperatively, first TSH level correlated significantly with the preoperative value (R=0.5779, P<0.001). Levothyroxine was prescribed to 16% of patients, with a mean dose of 0.92µg/kg/day. CONCLUSION: Patients with TSH>1.5 mIU/or remaining thyroid volume adjusted for body surface area<4.0mL/m2 should have intensified clinical and biological follow-up in the first year after surgery.

Prognostic value of pre-therapeutic FDG-PET radiomic analysis in gastro-esophageal junction cancer.

The main aim of this study was to evaluate the prognostic value of radiomic approach in pre-therapeutic 18F-fluorodeoxyglucose positron-emission tomography (FDG-PET/CT) in a large cohort of patients with gastro-esophageal junction cancer (GEJC). This was a retrospective monocenter study including 97 consecutive patients with GEJC who underwent a pre-therapeutic FDG-PET and were followed up for 3 years. Standard first-order radiomic PET indices including SUVmax, SUVmean, SUVpeak, MTV and TLG and 32 textural features (TFs) were calculated using LIFEx software on PET imaging. Prognostic significance of these parameters was assessed in univariate and multivariate analysis. Relapse-free survival (RFS) and overall survival (OS) were respectively chosen as primary and secondary endpoints. An internal validation cohort was used by randomly drawing one-third of included patients. The main characteristics of this cohort were: median age of 65 years [41-88], sex ratio H/F = 83/14, 81.5% of patients with a histopathology of adenocarcinoma and 43.3% with a stage IV disease. The median follow-up was 28.5 months [4.2-108.5]. Seventy-seven (79.4%) patients had locoregional or distant progression or recurrence and 71 (73.2%) died. In univariate analysis, SUVmean, Histogram-Entropy and 2 TFs (GLCM-Homogeneity and GLCM-Energy) were significantly correlated with RFS and OS, as well as 2 others TFs (GLRLM-LRE and GLRLM-GLNU) with OS only. In multivariate analysis, Histogram-Entropy remained an independent prognostic factor of both RFS and OS whereas SUVmean was an independent prognostic factor of OS only. These results were partially confirmed in our internal validation cohort of 33 patients. Our results suggest that radiomic approach reveals independent prognostic factors for survival in patients with GEJC.

SFE-AFCE-SFMN 2022 Consensus on the management of thyroid nodules : What is the role of functional imaging and isotopic treatment?

The SFE-AFCE-SFMN 2022 consensus deals with the management of thyroid nodules, a condition that is a frequent reason for consultation in endocrinology. In more than 90% of cases, patients are euthyroid, with benign non-progressive nodules that do not warrant specific treatment. The clinician's objective is to detect malignant thyroid nodules at risk of recurrence and death, toxic nodules responsible for hyperthyroidism or compressive nodules warranting treatment. The diagnosis and treatment of thyroid nodules requires close collaboration between endocrinologists, nuclear medicine physicians and surgeons, but also involves other specialists. Therefore, this consensus statement was established jointly by 3 societies: the French Society of Endocrinology (SFE), French Association of Endocrine Surgery (AFCE) and French Society of Nuclear Medicine (SFMN); the various working groups included experts from other specialties (pathologists, radiologists, pediatricians, biologists, etc.). This section deals with the role of thyroid scintigraphy in the diagnosis of autonomous thyroid nodules, nuclear medicine in nodules with indeterminate cytology and iodine treatment for autonomous thyroid nodules.

Smoking and diabetes interplay: A comprehensive review and joint statement.

Evidence shows that smoking increases the risk of pre-diabetes and diabetes in the general population. Among persons with diabetes, smoking has been found to increase the risk of all-cause mortality and aggravate chronic diabetic complications and glycemic control. The current paper, which is a joint position statement by the French-Speaking Society on Tobacco (Société Francophone de Tabacologie) and the French-Speaking Society of Diabetes (Société Francophone du Diabète), summarizes the data available on the association between smoking and diabetes and on the impact of smoking and smoking cessation among individuals with type 1, type 2, and gestational diabetes mellitus. It also provides evidence-based information about the pharmacological and behavioral strategies for smoking cessation in these patients.

Differences in perceived clinical knowledge uptake among health profession students and licensed clinicians receiving buprenorphine waiver training in Oregon.

Background: Addressing the opioid crisis requires an understanding of how to train both health professional students and practicing clinicians on medications for opioid use disorder (mOUD). We designed a robust evaluation instrument to assess the impact of training on perceived clinical knowledge in these different categories of learners. Methods: We enrolled 3rd and 4th year medical, physician assistant (PA), and nurse practitioner (NP) students, as well as practicing PAs, NPs, and physicians to undertake the Drug Addiction Treatment Act (DATA) Waiver Training for mOUD. We designed and implemented a cross-sectional survey to assess perceived change in clinical knowledge as a result of training in opioid use disorder and satisfaction with training. Results: Twenty-one MD/DO and 45 NP/PA students, and 24 practicing MD/DO and 27 NP/PAs completed the survey. Among health professional students (n = 66) and practicing clinicians (n =51), perceived clinical knowledge scores increased significantly (p < 0.001) for all 13 variables. Program evaluation scores for the buprenorphine waiver training were high with no statistical differences between students and practicing clinicians. Overall, the majority of participants indicated they would recommend the training to a colleague (Students' score = 4.84; practicing clinician scores = 4.53; scale = strongly disagree = 1 to strongly agree = 5). Conclusions: Our novel instrument allowed us to determine that the implementation of buprenorphine waiver trainings for health professional students and practicing clinicians leads to significant increases in perceived knowledge, interest and confidence in diagnosing and treating OUD. Although the buprenorphine waiver can now be obtained without training, many waivered providers still do not prescribe buprenorphine; integrating training into medical, NP, and PA curriculum for students and offering the training to practicing clinicians may increase confidence and uptake of mOUD.

Prevention of exercise-induced hypoglycemia in 12 patients with type 1 diabetes running the Paris Marathon using continuous glucose monitoring: A prospective, single-center observational study.

OBJECTIVE: To investigate the glycemic balance before, during and after the 2016 Paris Marathon using a real-time continuous glucose monitoring (RT-CGM) system in patients with type 1 diabetes mellitus in a prospective single-center observational study. METHODS: Inclusion criteria were as follows: type 1 diabetes mellitus; age ≥18 years; HbA1c < 9%. Participants performed two 2h-preparatory races (PR) before the Marathon and were monitored with RT-CGM 24h before, during and 72h after each race. Hypoglycemic events were prevented via carbohydrate intake / insulin dose adjustments. The primary outcome was area under the curve (AUC) < 70 and > 200 mg/dl and percentage of time spent in euglycemia, hypoglycemia, and hyperglycemia during the races. RESULTS: Twelve patients (2F/10M; median HbA1c=6.8%) were included and completed the study. Median AUC < 70 and time spent in hypoglycemia (< 70 mg/dl) during the PRs and Marathon were equal to 0. However, no hypoglycemic episodes occurred during Marathon, while two patients experienced hypoglycemia during PR1 and PR2. There was a significant increase in AUC > 200 mg/dl during races between PR2 and Marathon (P = 0.009) although the median time spent > 200mg/dl was not statistically different in Marathon versus PR2 (48.4% versus 18.4%; P = 0.09). Median time spent in euglycemia (70-200 mg/dl) was lower in Marathon versus PR2 (51.6 versus 58%; P = 0.03). CONCLUSION: Our study proposes a medical support protocol for extreme endurance physical activity in patients with type 1 diabetes mellitus. Our results suggest that RT-CGM, coupled with adjustments in carbohydrate intake and insulin doses, appears to be effective to prevent hypoglycemia during and after exercise.

Case report: Eosinophilic fasciitis induced by pembrolizumab with high FDG uptake on 18F-FDG-PET/CT.

Eosinophilic fasciitis (EF) is a rare connective tissue disorder causing inflammation and fibrosing of fascia. In this study, we present a very rare case of an immune checkpoint inhibitor (ICI)-induced EF revealed by 18F-fluorodesoxyglucose positron emission tomography (FDG-PET/CT) 20 months after the initiation of Pembrolizumab treatment of a relapsed non-small cell lung cancer (NSCLC). This study presents a 52-year-old Caucasian woman clinically presenting asthenia, inflammatory muscle, and joint pain associated with subcutaneous nodules and symmetrical edema of the lower limbs. Iterative 18FDG-PET/CT scans allow us to guide the therapeutic strategy due to this atypical ICI adverse event.

Prognostic Value of Whole-Body PET Volumetric Parameters Extracted from 68Ga-DOTATOC PET/CT in Well-Differentiated Neuroendocrine Tumors.

Our objective was to evaluate the prognostic value of somatostatin receptor tumor burden on 68Ga-DOTATOC PET/CT in patients with well-differentiated (WD) neuroendocrine tumors (NETs). Methods: We retrospectively analyzed the 68Ga-DOTATOC PET/CT scans of 84 patients with histologically confirmed WD NETs (51 grade 1, 30 grade 2, and 3 grade 3). For each PET/CT scan, all 68Ga-DOTATOC-avid lesions were independently segmented by 2 operators using a customized threshold based on the healthy liver SUVmax (LIFEx, version 5.1). Somatostatin receptor-expressing tumor volume (SRETV) and total lesion somatostatin receptor expression (TLSRE = SRETV × SUVmean) were extracted for each lesion, and then whole-body SRETV and TLSRE (SRETVwb and TLSREwb, respectively) were defined as the sum of SRETV and TLSRE, respectively, for all segmented lesions in each patient. Time to progression (TTP) was defined as the combination of disease-free survival in patients undergoing curative surgery (n = 10) and progression-free survival for patients with unresectable or metastatic disease (n = 74). TTP and overall survival were calculated by Kaplan-Meier analysis, log-rank testing, and the Cox proportional-hazards regression model. Results: After a median follow-up of 15.5 mo, disease progression was confirmed in 35 patients (41.7%) and 14 patients died. A higher SRETVwb (>39.1 cm3) and TLSREwb (>306.8 g) correlated significantly with a shorter median TTP (12 mo vs. not reached; P < 0.001). In multivariate analysis, SRETVwb (P = 0.005) was the only independent predictor of TTP regardless of histopathologic grade and TNM staging. Conclusion: According to our results, SRETVwb and TLSREwb extracted from 68Ga-DOTATOC PET/CT could predict TTP or overall survival and might have important clinical utility in the management of patients with WD NETs.

Sex disparities in COVID-19 outcomes of inpatients with diabetes: insights from the CORONADO study.

OBJECTIVE: Male sex is one of the determinants of severe coronavirus diseas-e-2019 (COVID-19). We aimed to characterize sex differences in severe outcomes in adults with diabetes hospitalized for COVID-19. METHODS: We performed a sex-stratified analysis of clinical and biological features and outcomes (i.e. invasive mechanical ventilation (IMV), death, intensive care unit (ICU) admission and home discharge at day 7 (D7) or day 28 (D28)) in 2380 patients with diabetes hospitalized for COVID-19 and included in the nationwide CORONADO observational study (NCT04324736). RESULTS: The study population was predominantly male (63.5%). After multiple adjustments, female sex was negatively associated with the primary outcome (IMV and/or death, OR: 0.66 (0.49-0.88)), death (OR: 0.49 (0.30-0.79)) and ICU admission (OR: 0.57 (0.43-0.77)) at D7 but only with ICU admission (OR: 0.58 (0.43-0.77)) at D28. Older age and a history of microvascular complications were predictors of death at D28 in both sexes, while chronic obstructive pulmonary disease (COPD) was predictive of death in women only. At admission, C-reactive protein (CRP), aspartate amino transferase (AST) and estimated glomerular filtration rate (eGFR), according to the CKD-EPI formula predicted death in both sexes. Lymphocytopenia was an independent predictor of death in women only, while thrombocytopenia and elevated plasma glucose concentration were predictors of death in men only. CONCLUSIONS: In patients with diabetes admitted for COVID-19, female sex was associated with lower incidence of early severe outcomes, but did not influence the overall in-hospital mortality, suggesting that diabetes mitigates the female protection from COVID-19 severity. Sex-associated biological determinants may be useful to optimize COVID-19 prevention and management in women and men.

Incidental Finding of a Parotid Basal Cell Adenoma With High Tracer Uptake on 68Ga-DOTATOC PET/CT.

ABSTRACT: A 67-year-old man was referred to our department to undergo a 68Ga-DOTATOC PET/CT during the systematic follow-up of a small intestine neuroendocrine tumor. PET revealed an incidental focal increased uptake of 68Ga-DOTATOC matching with a left intraparotid lesion on the combined contrast-enhanced CT, suggestive of a benign salivary tumor. An MRI was performed to characterize this lesion, and finally, the patient underwent surgery. Histological analysis confirmed the presence of a basal cell adenoma.

Diagnostic Value of Conventional PET Parameters and Radiomic Features Extracted from 18F-FDG-PET/CT for Histologic Subtype Classification and Characterization of Lung Neuroendocrine Neoplasms.

AIM: To evaluate if conventional Positron emission tomography (PET) parameters and radiomic features (RFs) extracted by 18F-FDG-PET/CT can differentiate among different histological subtypes of lung neuroendocrine neoplasms (Lu-NENs). METHODS: Forty-four naïve-treatment patients on whom 18F-FDG-PET/CT was performed for histologically confirmed Lu-NEN (n = 46) were retrospectively included. Manual segmentation was performed by two operators allowing for extraction of four conventional PET parameters (SUVmax, SUVmean, metabolic tumor volume (MTV), and total lesion glycolysis (TLG)) and 41 RFs. Lu-NENs were classified into two groups: lung neuroendocrine tumors (Lu-NETs) vs. lung neuroendocrine carcinomas (Lu-NECs). Lu-NETs were classified according to histological subtypes (typical (TC)/atypical carcinoid (AC)), Ki67-level, and TNM staging. The least absolute shrink age and selection operator (LASSO) method was used to select the most predictive RFs for classification and Pearson correlation analysis was performed between conventional PET parameters and selected RFs. RESULTS: PET parameters, in particular, SUVmax (area under the curve (AUC) = 0.91; cut-off = 5.16) were higher in Lu-NECs vs. Lu-NETs (p < 0.001). Among RFs, HISTO_Entropy_log10 was the most predictive (AUC = 0.90), but correlated with SUVmax/SUVmean (r = 0.95/r = 0.94, respectively). No statistical differences were found between conventional PET parameters and RFs (p > 0.05) and TC vs. AC classification. Conventional PET parameters were correlated with N+ status in Lu-NETs. CONCLUSION: In our study, conventional PET parameters were able to distinguish Lu-NECs from Lu-NETs, but not TC from AC. RFs did not provide additional information.

Prospective study of dynamic whole-body 68Ga-DOTATOC-PET/CT acquisition in patients with well-differentiated neuroendocrine tumors.

To present the feasibility of a dynamic whole-body (DWB) 68Ga-DOTATOC-PET/CT acquisition in patients with well-differentiated neuroendocrine tumors (WD-NETs). Sixty-one patients who underwent a DWB 68Ga-DOTATOC-PET/CT for a histologically proven/highly suspected WD-NET were prospectively included. The acquisition consisted in single-bed dynamic acquisition centered on the heart, followed by the DWB and static acquisitions. For liver, spleen and tumor (1-5/patient), Ki values (in ml/min/100 ml) were calculated according to Patlak's analysis and tumor-to-liver (TLR-Ki) and tumor-to-spleen ratios (TSR-Ki) were recorded. Ki-based parameters were compared to static parameters (SUVmax/SUVmean, TLR/TSRmean, according to liver/spleen SUVmean), in the whole-cohort and according to the PET system (analog/digital). A correlation analysis between SUVmean/Ki was performed using linear and non-linear regressions. Ki-liver was not influenced by the PET system used, unlike SUVmax/SUVmean. The regression analysis showed a non-linear relation between Ki/SUVmean (R2 = 0.55,0.68 and 0.71 for liver, spleen and tumor uptake, respectively) and a linear relation between TLRmean/TLR-Ki (R2 = 0.75). These results were not affected by the PET system, on the contrary of the relation between TSRmean/TSR-Ki (R2 = 0.94 and 0.73 using linear and non-linear regressions in digital and analog systems, respectively). Our study is the first showing the feasibility of a DWB 68Ga-DOTATOC-PET/CT acquisition in WD-NETs.

Impact of segmentation and discretization on radiomic features in 68Ga-DOTA-TOC PET/CT images of neuroendocrine tumor.

OBJECTIVE: To identify the impact of segmentation methods and intensity discretization on radiomic features (RFs) extraction from 68Ga-DOTA-TOC PET images in patients with neuroendocrine tumors. METHODS: Forty-nine patients were retrospectively analyzed. Tumor contouring was performed manually by four different operators and with a semi-automatic edge-based segmentation (SAEB) algorithm. Three SUVmax fixed thresholds (20, 30, 40%) were applied. Fifty-one RFs were extracted applying two different intensity rescale factors for gray-level discretization: one absolute (AR60 = SUV from 0 to 60) and one relative (RR = min-max of the VOI SUV). Dice similarity coefficient (DSC) was calculated to quantify segmentation agreement between different segmentation methods. The impact of segmentation and discretization on RFs was assessed by intra-class correlation coefficients (ICC) and the coefficient of variance (COVL). The RFs' correlation with volume and SUVmax was analyzed by calculating Pearson's correlation coefficients. RESULTS: DSC mean value was 0.75 ± 0.11 (0.45-0.92) between SAEB and operators and 0.78 ± 0.09 (0.36-0.97), among the four manual segmentations. The study showed high robustness (ICC > 0.9): (a) in 64.7% of RFs for segmentation methods using AR60, improved by applying SUVmax threshold of 40% (86.5%); (b) in 50.9% of RFs for different SUVmax thresholds using AR60; and (c) in 37% of RFs for discretization settings using different segmentation methods. Several RFs were not correlated with volume and SUVmax. CONCLUSIONS: RFs robustness to manual segmentation resulted higher in NET 68Ga-DOTA-TOC images compared to 18F-FDG PET/CT images. Forty percent SUVmax thresholds yield superior RFs stability among operators, however leading to a possible loss of biological information. SAEB segmentation appears to be an optimal alternative to manual segmentation, but further validations are needed. Finally, discretization settings highly impacted on RFs robustness and should always be stated.