Relation Between F-18 FDG Uptake of PET/CT and BRAFV600E Mutation in Papillary Thyroid Cancer

Significance of incidental focal fluorine-18 fluorodeoxyglucose uptake in colon/rectum, thyroid, and prostate: With a brief literature review

BACKGROUND

Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT), a functional imaging method, is usually performed on the entire torso, and regions of unexpected suspicious focal hypermetabolism are not infrequently observed. Among the regions, colon, thyroid, and prostate were found to be the common organs in a recent umbrella review. Some studies reported that a high rate of malignancy was shown in incidentally identified focal hypermetabolic regions and suggested that further examinations should not be ignored.

AIM

To investigate the malignancy rate of incidental focal FDG uptake, useful PET parameters and their cutoffs in discrimination between malignant and benign lesions.

METHODS

Retrospectively, the final reports of 16510 F-18 FDG PET/CT scans performed at our hospital between January 2016 and March 2022 were reviewed to identify incidentally observed FDG uptake in the colon/rectum, thyroid, and prostate. The scans of patients with current or prior malignancies at each corresponding location, without the final reports of histopathology or colonoscopy (for colon and rectum) for the corresponding hypermetabolic regions, or with diffuse (not focal) hypermetabolism were excluded. Finally, 88 regions of focal colorectal hypermetabolism in 85 patients (48 men and 37 women with mean age 67.0 ± 13.4 years and 63.4 ± 15.8 years, respectively), 48 focal thyroid uptakes in 48 patients (12 men and 36 women with mean age 62.2 ± 13.1 years and 60.8 ± 12.4 years, respectively), and 39 focal prostate uptakes in 39 patients (mean age 71.8 ± 7.5 years) were eligible for this study. For those unexpected focal hypermetabolic regions, rates of malignancy were calculated, PET parameters, such as standardized uptake value (SUV), capable of distinguishing between malignant and benign lesions were investigated, and the cutoffs of those PET parameters were determined by plotting receiver operating characteristic curves.

RESULTS

In the colon and rectum, 29.5% (26/88) were malignant and 33.0% (29/88) were premalignant lesions. Both SUVmax and SUVpeak differentiated malignant/premalignant from benign lesions, however, no parameters could distinguish malignant from premalignant lesions. Higher area under the curve was shown with SUVmax (0.752, 95%CI: 0.649-0.856, P < 0.001) and the cutoff was 7.6. In the thyroid, 60.4% (29/48) were malignant. The majority were well-differentiated thyroid cancers (89.7%, 26/29). The results of BRAF mutation tests were available for 20 of the 26 well-differentiated thyroid cancers and all 20 had the mutation. Solely SUVmax differentiated malignant from benign lesions and the cutoff was 6.9. In the prostate, 56.4% (22/39) were malignant. Only SUVmax differentiated malignant from benign lesions and the cutoff was 3.8. Overall, among the 175 focal hypermetabolic regions, 60.6% (106/175) were proven to be malignant and premalignant (in colon and rectum) lesions.

CONCLUSION

Approximately 60% of the incidentally observed focal F-18 FDG uptake in the colon/rectum, thyroid, and prostate were found to be malignant. Of the several PET parameters, SUVmax was superior to others in distinguishing between malignant/premalignant and benign lesions. Based on these findings, incidental focal hypermetabolism should not be ignored and lead physicians to conduct further investigations with greater confidence.

Characterization of focal hypermetabolic thyroid incidentaloma: An analysis with F-18 fluorodeoxyglucose positron emission tomography/computed tomography parameters

BACKGROUND

Incidentally found thyroid tumor (thyroid incidentaloma, TI) on F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is reported in 2.5%-5% of patients being investigated for non-thyroid purposes. Up to 50% of these cases have been diagnosed to be malignant by cytological/histological results. Ultrasonography (US) and fine-needle aspiration cytology are recommended for thyroid nodules with high FDG uptake (hypermetabolism) that are 1 cm or greater in size. It is important to accurately determine whether a suspicious hypermetabolic TI is malignant or benign.

AIM

To distinguish malignant hypermetabolic TIs from benign disease by analyzing F-18 FDG PET-CT parameters and to identify a cut-off value.

METHODS

Totally, 12761 images of patients who underwent F-18 FDG PET-CT for non-thyroid purposes at our hospital between January 2016 and December 2020 were retrospectively reviewed, and 339 patients [185 men (mean age: 68 ± 11.2) and 154 women (mean age: 63 ± 15.0)] were found to have abnormal, either focal or diffuse, thyroid FDG uptake. After a thorough review of their medical records, US, and cytological/histological reports, 46 eligible patients with focal hypermetabolic TI were included in this study. The TIs were categorized as malignant and benign according to the cytological/histological reports, and four PET parameters [standardized uptake value (SUV)_max, SUV_peak, SUV_mean, and metabolic tumor volume (MTV)] were measured on FDG PET-CT. Total lesion glycolysis (TLG) was calculated by multiplying the SUV_mean by MTV. Both parametric and non-parametric methods were used to compare the five parameters between malignant and benign lesions. Receiver operating characteristic (ROC) curve analysis was performed to identify a cut-off value.

RESULTS

Each of the 46 patients [12 men (26.1%; mean age: 62 ± 13.1 years) and 34 women (73.9%; mean age: 60 ± 12.0 years)] with focal hypermetabolic TIs had one focal hypermetabolic TI. Among them, 26 (56.5%) were malignant and 20 (43.5%) were benign. SUV_max, SUV_peak, SUV_mean, and TLG were all higher in malignant lesions than benign ones, but the difference was statistically significant (P = 0.012) only for SUV_max. There was a positive linear correlation (r = 0.339) between SUV_max and the diagnosis of malignancy. ROC curve analysis for SUV_max revealed an area under the curve of 0.702 (P < 0.05, 95% confidence interval: 0.550-0.855) and SUV_max cut-off of 8.5 with a sensitivity of 0.615 and a specificity of 0.789.

CONCLUSION

More than half of focal hypermetabolic TIs on F-18 FDG PET-CT were revealed as malignant lesions, and SUV_max was the best parameter for discriminating between malignant and benign disease. Unexpected focal hypermetabolic TIs with the SUV_max above the cut-off value of 8.5 may have a greater than 70% chance of malignancy; therefore, further active assessment is required.

Relationship between clinicopathologic factors and FDG avidity in radioiodine-negative recurrent or metastatic differentiated thyroid carcinoma

BACKGROUND

In this study, we investigated the relationship between clinicopathologic factors, BRAFV600E mutation status and [18F] F-fluoro-2-deoxyglucose (FDG) avidity in patients with radioiodine (RAI)-negative recurrent or metastatic differentiated thyroid cancer (DTC).

METHODS

From 2015 to 2018 all patients with suspected recurrent or metastatic radioiodine-negative DTC patients who underwent FDG positron emission tomography/computed tomography (PET/CT) were retrospectively reviewed. Suspected lesions on FDG PET/CT were biopsied and underwent BRAFV600E mutation testing by immunohistochemistry and real-time PCR. Tumor size, recurrent versus metastatic disease, histopathologic features including classical type versus aggressive subtypes (poorly differentiated, tall cell, columnar cell, hobnail variants) and BRAFV600E mutation status were correlated with the SUVmax of highest hypermetabolic lesions on FDG PET/CT by the univariate analysis using logistic regression.

RESULTS

Sixty-three consecutive patients, 55 (87.3%) female, with median age of 48 (range 17-81) were included. The majority of patients had BRAFV600E mutation and classical subtype, 55/63 (87.3%) and 45/63(71.4%), respectively. Thyroglobulin at the time of suspected recurrence was 262.7 ng/ml (range 16.3-1000) and patients received a median 3 prior RAI treatments. Fifty-four patients (85.7%) had local recurrence. The majority of patients 58/63 (92.1%) had FDG-avid disease on PET/CT. On univariate analysis, tumor size aggressive histopathologic types and distant metastasis are the significant factors for predicting FDG uptake, p = 0.04, p = 0.001 and p = 0.004 respectively. Although FDG uptake of BRAFV600E bearing recurrent/metastatic RAIR DTC lesions was higher than those without the mutation, the difference did not reach statistical significance, SUVmax of 7.11 versus 4.91, respectively, p = 0.2.

CONCLUSION

The majority of recurrent or metastatic RAI-negative DTC have BRAFV600E mutation and detectable disease on FDG PET/CT. FDG avidity of the recurrent or metastatic RAI-negative DTC is independently associated with the aggressive histopathologic features.

Clinical application and research advancement of positron emission tomography/computed tomography in colorectal cancer

Colorectal cancer is one of the most common malignant tumors of the digestive system. Early diagnosis and accurate staging and restaging of tumors are the preconditions for standardized treatment of colorectal cancer, which is conducive to the selection of treatment options and the evaluation of prognosis, as well as the improvement of patients' quality of life. With the popularization of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT), its value in the diagnosis, staging and restaging, treatment decision-making, and efficacy and prognosis assessment of colorectal cancer is becoming increasingly important. This review briefly introduces the application and advancement of PET/CT in the diagnosis and treatment of colorectal cancer, in the hope that clinicians can have a more comprehensive understanding of the significance of PET/CT in the diagnosis and treatment of colorectal cancer.

Prognostic and predictive value of nuclear imaging in endocrine oncology

In the last few years, the role and use of medical technologies in (neuro)endocrine oncology has greatly evolved allowing not only important diagnostic information but also prognostic stratification in different clinical situations. The terms "prognostic" and "predictive" are commonly used to describe the relationships between biomarkers and patients' clinical outcomes but have quite different meaning. The present work discusses the prognostic and predictive value of nuclear medicine imaging. It critically reviews the clinical significance and potential impact of molecular examinations on follow-up and therapeutic strategies in patients with neuroendocrine neoplasms, thyroid tumors, and adrenal malignancies.

Metabolic reprogramming and its clinical application in thyroid cancer

Warburg found that tumor cells exhibit high-level glycolysis, even under aerobic condition, which is known as the ‘Warburg effect’. As systemic changes in the entire metabolic network are gradually revealed, it is recognized that metabolic reprogramming has gone far beyond the imagination of Warburg. Metabolic reprogramming involves an active change in cancer cells to adapt to their biological characteristics. Thyroid cancer is a common endocrine malignant tumor whose metabolic characteristics have been studied in recent years. Some drugs targeting tumor metabolism are under clinical trial. This article reviews the metabolic changes and mechanisms in thyroid cancer, aiming to find metabolic-related molecules that could be potential markers to predict prognosis and metabolic pathways, or could serve as therapeutic targets. Our review indicates that knowledge in metabolic alteration has potential contributions in the diagnosis, treatment and prognostic evaluation of thyroid cancer, but further studies are needed for verification as well.

Risk factors for cervical lymph node metastasis in papillary thyroid microcarcinoma: a study of 1,587 patients

Objective

The purposes of this study were to identify risk factors for cervical lymph node metastasis and to examine the association between BRAF^V600E status and clinical features in papillary thyroid microcarcinoma (PTMC).

Methods

A total of 1,587 patients with PTMC, treated in Tianjin Medical University Cancer Institute and Hospital from January 2011 to March 2013, underwent retrospective analysis. We reviewed and analyzed factors including clinical results, pathology records, ultrasound results, and BRAF^V600E status.

Results

Multivariate logistic regression analyses demonstrated that gender (male) [odds ratio (OR) = 1.845, P = 0.000], age (< 45 years)(OR = 1.606,P = 0.000), tumor size (> 6 mm) (OR = 2.137,P = 0.000), bilateralism (OR = 2.011, P = 0.000) and extrathyroidal extension (OR = 1.555, P = 0.001) served as independent predictors of central lymph node metastasis (CLNM). Moreover, CLNM (OR = 29.354, P = 0.000) served as an independent predictor of lateral lymph node metastasis (LLNM). Among patients with a solitary primary tumor, those with tumor location in the lower third of the thyroid lobe or the isthmus were more likely to experience CLNM (P < 0.05). Univariate analyses indicated that CLNM, LLNM, extrathyroidal extension, and multifocality were not significantly associated with BRAF^V600E mutation.

Conclusions

The present study suggested that prophylactic neck dissection of the central compartment should be considered in patients with PTMC, particularly in men with tumor size greater than 6 mm, age less than 45 years, extrathyroidal extension, and tumor bilaterality. Among patients with PTMC, BRAF^V600E mutation is not significantly associated with prognostic factors. For a better understanding of surgical management of PTMC and the risk factors, we recommend multicenter research and long-term follow-up.

MicroRNA-9-5p functions as a tumor suppressor in papillary thyroid cancer via targeting BRAF

MicroRNAs (miRNAs/miRs) are widely studied as key regulators of gene expression and are involved in various diseases by affecting the miRNA-mediated regulatory function. BRAF is an important oncogene in the regulation of cell proliferation and apoptosis. In the present study, reverse transcription-quantitative polymerase chain reaction was used to determine the expression levels of miR-9-5p and BRAF mRNA in patients with papillary thyroid cancer (PTC). Western blotting was used to detect BRAF protein level. A luciferase assay was used to verify the miR-9-5p target site in BRAF. Cell Counting Kit-8 and flow cytometry were used to assess cell proliferation, and apoptosis, respectively. In the present study, it was demonstrated that miR-9-5p is downregulated in malignant PTC. Using bioinformatics analysis, miR-9-5p was predicted to target the human BRAF 3'-untranslated region (3'-UTR). A dual-luciferase assay demonstrated that miR-9-5p downregulated BRAF expression by directly targeting its 3'-UTR. Mutations in the 3'-UTR of BRAF completely abolished its interaction with miR-9-5p. Expression of exogenous miRNA that mimics miR-9-5p miRNA decreased BRAF protein and mRNA levels, while suppression of endogenous miR-9-5p resulted in an increase in BRAF protein, and mRNA levels. Furthermore, regulation of miR-9-5p was observed to suppress the viability of PTC cells by inducing apoptosis. Consistently, downregulation of miR-9-5p promoted proliferation of PTC cells by inhibiting the apoptosis of cells. In conclusion, the present study demonstrated that miR-9-5p may perform an important role in PTC prognosis and therapy.

Relationship Between 18F-fluorodeoxyglucose Accumulation and the BRAF V600E Mutation in Papillary Thyroid Cancer

BACKGROUND

To determine whether ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG)-PET/CT is useful for predicting the BRAF ^V600E mutation status of a primary papillary thyroid carcinoma (PTC).

METHODS

A retrospective analysis was performed in 108 patients who underwent ¹⁸F-FDG positron emission tomography-computed tomography (PET/CT) for staging before thyroidectomy and BRAF analysis in biopsy-confirmed PTC. The maximum standardized uptake value (SUV_max) of the primary tumor was calculated according to FDG accumulation. Univariate and multivariate analyses were performed to assess the association between the SUV_max and clinicopathological variables.

RESULTS

The BRAF ^V600E mutation was detected in 71 of 108 (65.7%) patients. In all subjects, the tumor size and BRAF ^V600E mutation were independently related to the SUV_max according to multivariate analyses (P = 0.002 and 0.007, respectively). The SUV_max was significantly higher in tumors with the BRAF ^V600E mutation than in tumors with wild-type BRAF (10.24 ± 11.89 versus 4.02 ± 3.86; P = 0.007). In the tumor size >1 cm subgroup, the BRAF ^V600E mutation was the only factor significantly associated with the SUV_max (P = 0.016). A SUV_max cutoff level of 4.9 was determined to be significant for predicting the BRAF ^V600E mutation status (sensitivity 77.4%, specificity 100.0%, area under the curve 0.929; P < 0.0001) according to ROC curve analysis.

CONCLUSIONS

The BRAF ^V600E mutation is independently associated with high ¹⁸F-FDG uptake in PTC, especially in those with a tumor size >1 cm.

Radiomics in Oncological PET/CT: Clinical Applications

18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is widely used for staging, evaluating treatment response, and predicting prognosis in malignant diseases. FDG uptake and volumetric PET parameters such as metabolic tumor volume have been used and are still used as conventional PET parameters to assess biological characteristics of tumors. However, in recent years, additional features derived from PET images by computational processing have been found to reflect intratumoral heterogeneity, which is related to biological tumor features, and to provide additional predictive and prognostic information, which leads to the concept of radiomics. In this review, we focus on recent clinical studies of malignant diseases that investigated intratumoral heterogeneity on PET/CT, and we discuss its clinical role in various cancers.

Clinicopathological characteristics including BRAF V600E mutation status and PET/CT findings in papillary thyroid carcinoma

OBJECTIVE

We assessed the associations between FDG uptake in primary papillary thyroid carcinomas (PTCs) and clinicopathological features, including the BRAF V600E mutation, using quantitative and qualitative analyses of preoperative PET/CT data.

DESIGN AND PATIENTS

This was a retrospective review of 106 patients with PTC who underwent PET/CT scans between February 2009 and January 2011 before undergoing total thyroidectomy. Data collected from surgical specimens were compared with FDG uptake in the primary tumour using quantitative and qualitative analyses of preoperative PET/CT data. Clinicopathological data included the primary tumour size, subtype, capsular invasion, extrathyroid extension, multifocality, BRAF V600E mutation status, lymph node metastasis and distant metastasis.

RESULTS

The SUVmax of the primary tumour was significantly higher in patients with a primary tumour >1 cm, extrathyroid extension or the BRAF V600E mutation than in patients without these features (P<.001, .049 and <.001). Univariate analyses showed that primary tumour size, extrathyroid extension and BRAF V600E mutation status were associated with the SUVmax of the PTC. Multivariate analysis indicated that primary tumour size and the BRAF V600E mutation were associated with the SUVmax of the PTC. In a visual assessment, the primary tumour size was larger in FDG-avid than in non-FDG-avid PTCs (P<.001). There was no significant difference in the presence of multifocality, thyroid capsular invasion, extrathyroid extension, BRAF V600E mutation, lymph node metastasis or distant metastasis between FDG-avid and non-FDG-avid PTCs.

CONCLUSIONS

Primary tumour size and the BRAF V600E mutation are significant factors associated with the SUVmax on preoperative PET/CT in patients with PTC.

Correlation of BRAF mutation and SUVmax levels in thyroid cancer patients incidentally detected in 18F-fluorodeoxyglucose positron emission tomography

The prognostic importance of ¹⁸F-fluorodeoxyglucose avidity in primary thyroid tumor and molecular basis responsible for its mechanism has not yet been well characterized. In this study, we aimed to evaluate the correlation between the maximum standardized uptake levels and B-type Raf kinase mutation positivity in incidentally detected papillary thyroid cancer patients during ¹⁸F-fluorodeoxyglucose positron emission tomography examination. We retrospectively evaluated 6873 ¹⁸F-fluorodeoxyglucose-positron emission tomography scans of consecutive subjects from a database search for tumor staging in 2014 at our hospital Nuclear Medicine Center. In total, 135 patients had focal ¹⁸F-fluorodeoxyglucose uptake in the thyroid. Of these, 76 patients had fine-needle aspiration biopsy. ¹⁸F-fluorodeoxyglucose-maximum standardized uptake of the positron emission tomography-detected nodules was recorded. B-type Raf kinase (V600E) mutation and p53 protein expression were evaluated in papillary thyroid cancer patients. The incidence of thyroid incidentaloma in ¹⁸F-fluorodeoxyglucose-maximum standardized uptake scans was 2 % (135/6873). Of the 76 patients evaluated, 41 % (n = 31) were diagnosed papillary thyroid cancer. B-type Raf kinase mutation was positive in 51 % (17/30) of the papillary thyroid cancer patients. Maximum standardized uptake levels of the nodules (≥1 cm) were significantly higher in B-type Raf kinase-mutated papillary thyroid cancer patients than in non-mutated patients [16.6 (10.4-27.9) vs. 9.7 (6.8-11.1); P = 0.007]. Correlation analysis revealed that maximum standardized uptake was significantly associated with B-type Raf kinase mutation positivity (r = 0.519; P = 0.005). Logistic regression analysis showed an association between maximum standardized uptake and B-type Raf kinase mutation positivity even after adjustment for age and gender (P = 0.01). B-type Raf kinase mutation is closely related to ¹⁸F-fluorodeoxyglucose-positron emission tomography maximum standardized uptake levels in patients with incidentally detected papillary thyroid cancer.

Designing and Developing PET-Based Precision Model in Thyroid Carcinoma: The Potential Avenues for a Personalized Clinical Care

This communication enumerates the current uses and potential areas where PET could be clinically utilized for developing "precision medicine" type model in thyroid carcinoma. (1) In routine clinics, PET imaging (with fluorodeoxyglucose [FDG]) is utilized to investigate patients of differentiated thyroid carcinoma (DTC) with high thyroglobulin and negative iodine scintigraphy (TENIS) and in medullary carcinoma thyroid (MCT) when the tumor markers (eg, calcitonin and carcino embryonic antigen [CEA]) are raised postoperatively (PET with FDG, ⁶⁸Ga-DOTA-NOC/TATE, FDOPA). Both are examples of management personalization, where PET-computed tomography (CT) has been found substantially useful in detecting sites of metastatic disease and making decision with regard to feasibility and planning of surgery on an individual patient basis. (2) The next important area of management personalization is in patients of TENIS with metastatic disease not amenable to surgery through examining FDG-PET findings in tandem with radio iodine scan and ⁶⁸Ga-DOTA-TATE/NOC PET/CT. Heterogeneous behavior of the metastatic lesions is frequently observed clinically: analyzing the findings of three studies aids in sub-segmenting patients into subgroups and thereby deciding upon the best approach (observation with LT4 suppression vs PRRT vs tyrosine kinase inhibitors) that could be individualized in a given case. (3) In metastatic/inoperable MCT, ⁶⁸Ga-DOTA-TATE/NOC PET-CT helps in deciding upon feasibility of targeted PRRT in an individual patient and helps in follow-up and response evaluation. (4) Disease prognostification with FDG-PET is evolving both in DTC and MCT, where FDG avidity would indicate an aggressive biology, though the implication of this from treatment viewpoint is unclear at this point. Conversely, a negative FDG-PET in DTC and TENIS would suggest a favorable prognosis in an individual. (5) Iodine-124 PET/CT has the added potential of obtaining lesional dosimetry compared to the SPECT approach, and could help in selecting appropriate doses on an individual basis.

Papillary thyroid microcarcinoma: time to shift from surgery to active surveillance?

The incidence of differentiated thyroid cancer is increasing greatly in high-income countries. Roughly 50% of this increase is attributable to the identification of intrathyroidal papillary thyroid microcarcinomas. Since mortality associated with these tumours remains low and stable, the increasing diagnosis has led to concerns about overdiagnosis and overtreatment. Management of papillary thyroid microcarcinomas should take into account the reported absence of mortality when diagnosed in the absence of lymph node metastases and distant metastases, as shown even in recent studies promoting active surveillance; a low recurrence rate of 1-5%; and the risk of permanent complications from surgery that cannot be decreased to less than 1-3%, even in high-volume tertiary care centres with experienced surgeons. On the basis of these data, active surveillance with curative intent, in which active treatment is delayed until the cancer shows signs of significant progression to avoid side-effects of treatment, should be considered in properly selected patients.

(18)F-FDG PET/CT imaging in rectal cancer: relationship with the RAS mutational status

OBJECTIVE

Treating metastatic colorectal cancer with anti-EGFR monoclonal antibodies is recommended only for patients whose tumour does not harbour mutations of KRAS or NRAS. The aim of this study was to investigate the biology of rectal cancers and specifically to evaluate the relationship between fluorine-18 fludeoxyglucose ((18)F-FDG) positron emission tomography (PET) intensity and heterogeneity parameters and their mutational status.

METHODS

151 patients with newly diagnosed rectal cancer were included in this retrospective study. All patients underwent a baseline (18)F-FDG PET/CT within a median time interval of 27 days of tumour tissue sampling, which was performed before any treatment. Standardized uptake values (SUVs), volume-based parameters and texture analysis were studied. We retrospectively performed KRAS genotyping on codons 12, 13, 61, 117 and 146, NRAS genotyping on codons 12, 13 and 61 and BRAF on codon 600. Associations between PET/CT parameters and the mutational status were assessed using univariate and multivariate analysis.

RESULTS

83 (55%) patients had an RAS mutation: 74 KRAS and 9 NRAS, while 68 patients had no mutation (wild-type tumours). No patient had BRAF mutation. First-order features based on intensity histogram analysis were significantly associated with RAS mutations: maximum SUV (SUVmax) (p-value = 0.002), mean SUV (p-value = 0.006), skewness (p-value = 0.049), SUV standard deviation (p-value = 0.001) and SUV coefficient of variation (SUVcov) (p-value = 0.001). Both SUVcov and SUVmax showed an area under the curve of 0.65 with sensitivity of 56% and 69%, respectively, and specificity of 64% and 52%, respectively. None of the volume-based (metabolic tumour volume and total lesion glycolysis), nor local or regional textural features were associated with the presence of RAS mutations.

CONCLUSION

Although rectal cancers with KRAS or NRAS mutations display a significantly higher glucose metabolism than wild-type cancers, the accuracy of the currently proposed quantitative metrics extracted from (18)F-FDG PET/CT is not sufficiently high for playing a meaningful clinical role.

ADVANCES IN KNOWLEDGE

RAS-mutated rectal cancers have a significantly higher glucose metabolism. However, the accuracy of (18)F-FDG PET/CT quantitative metrics is not as such as the technique could play a clinical role.