Focal Colonic FDG Activity with PET/CT: Guidelines for Recommendation of Colonoscopy

Predictive value of 18F-fluorodeoxyglucose PET/CT in histological grade of incidental colorectal adenoma

BACKGROUND

18F-fluorodeoxyglucose (18F-FDG) positron-emission tomography/computed tomography (PET/CT) as an imaging modality for the whole body has shown its value in detecting incidental colorectal adenoma. In clinical practice, adenomatous polyps can be divided into three groups: low-grade intraepithelial neoplasia (LGIN), high-grade intraepithelial neoplasia (HGIN) and cancer, which can lead to different clinical management. However, the relationship between the 18F-FDG PET/CT SUVmax and the histological grade of adenomatous polyps is still not established, which is a challenging but valuable task.

METHODS

This retrospective study included 255 patients with colorectal adenoma (CRA) or colorectal adenocarcinomas (AC) who had corresponding 18F-FDG uptake incidentally found on PET/CT. The correlations of SUVmax with pathological characteristics and tumor size were assessed. Neoplasms were divided into LGIN, HGIN, and AC according to histological grade. Receiver operating characteristic (ROC) analysis was applied to evaluate the predictive value of the SUVmax-only model and comprehensive models which were established with imaging and clinical predictors identified by univariate and multivariate analysis.

RESULTS

The SUVmax was positively correlated with histological grades (r=0.529, P<0.001). Univariate and multivariate analysis showed that SUVmax was an independent risk factor among all groups except between HGIN and AC. The area under the curves (AUCs) of the comprehensive model for distinguishing between AC and adenoma, LGIN and HIGN, LGIN and AC, and HGIN and AC were 0.886, 0.780, 0.945, 0.733, respectively, which is statistically higher than the AUCs of the SUVmax-only model with 0.812, 0.733, 0.863, and 0.688, respectively.

CONCLUSIONS

As an independent risk factor, SUVmax based on 18F-FDG PET/CT is highly associated with the histological grade of CRA. Thus, 18F-FDG PET/CT can serve as a noninvasive tool for precise diagnosis and assist in the preoperative formulation of treatment strategies for patients with incidental CRA.

Focal incidental colorectal fluorodeoxyglucose uptake: Should it be spotlighted?

Fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) has emerged as a cornerstone in cancer evaluation imaging, with a well-established history spanning several years. This imaging modality, encompassing the examination of the body from the base of the skull to the upper thighs, comprehensively covers the chest and abdominopelvic regions in a singular scan, allowing for a holistic assessment of nearly the entire body, including areas of marginal interest. The inherent advantage of this expansive scan range lies in its potential to unveil unexpected incidental abnormal hypermetabolic areas. The identification of incidental focal FDG uptake within colorectal regions during PET/CT scans is not an uncommon occurrence, albeit fraught with challenges associated with non-specific FDG uptake. The presence of benign colorectal lesions or physiological uptake poses a particular obstacle, as these may manifest with FDG uptake levels that mimic malignancy. Consequently, physicians are confronted with a diagnostic dilemma when encountering abnormal FDG uptake in unexpected colorectal areas. Existing studies have presented divergent results concerning these uptakes. Standardized uptake value and its derivatives have served as pivotal metrics in quantifying FDG uptake in PET images. In this article, we aim to succinctly explore the distinctive characteristics of FDG, delve into imaging findings, and elucidate the clinical significance of incidental focal colorectal uptake. This discussion aims to contribute valuable insights into the nuanced interpretation of such findings, fostering a comprehensive understanding.

A novel objective method for discriminating pathological and physiological colorectal uptake in the lower abdominal region using whole-body dynamic 18F-FDG-PET

OBJECTIVES

To investigate whether the center-of-mass shift distance (CMSD) analysis on whole-body dynamic positron emission tomography (WBD-PET) with continuous bed motion is an objective index for discriminating pathological and physiological uptake in the lower abdominal colon.

METHODS

We retrospectively analyzed the CMSD in 39 patients who underwent delayed imaging to detect incidental focal uptake that was difficult to determine as pathological and physiological on a conventional early-PET (early) image reconstructed by 5-phase WBD-PET images. The CMSD between each phase of WBD-PET images and between conventional early and delayed (two-phase) PET images were classified into pathological and physiological uptake groups based on endoscopic histology or other imaging diagnostics. The diagnostic performance of CMSD analysis on WBD-PET images was evaluated by receiver operator characteristic (ROC) analysis and compared to that of two-phase PET images.

RESULTS

A total of 66 incidental focal uptake detected early image were classified into 19 and 47 pathological and physiological uptake groups, respectively. The CMSD on WBD-PET and two-phase PET images in the pathological uptake group was significantly lower than that in the physiological uptake group (p < 0.01), respectively. The sensitivity, specificity, and accuracy in CMSD analysis on WBD-PET images at the optimal cutoff of 5.2 mm estimated by the Youden index were 94.7%, 89.4%, and 89.4%, respectively, which were not significantly different (p = 0.74) from those of two-phase PET images.

CONCLUSIONS

The CMSD analysis on WBD-PET was useful in discriminating pathological and physiological colorectal uptake in the lower abdominal region, and its diagnostic performance was comparable to that of two-phase PET images. We suggested that CMSD analysis on WBD-PET images would be a novel objective method to omit unnecessary additional delayed imaging.

Prevalence and Clinical Significance of Incidental Focal 18F-FDG Uptake in Colon on PET/CT Imaging

Objectives:

The present study aimed to identify the prevalence of focal uptake in the colon on ¹⁸fluorine-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) studies performed for the evaluation of malignancies other than colon, to detect the rate of malignancy in incidental focal ¹⁸F-FDG avid colonic lesions and to investigate if any possible role of maximum standardized uptake value (SUV_max) values in the discrimination of malignant lesions from premalignant and benign ones exist.

Methods:

We retrospectively reviewed the files of 8,017 patients with known or suspected malignancy, who underwent whole-body ¹⁸F-FDG PET/CT at our institution during the period November 2017 to November 2019. Patients showing a single site of focally increased colonic ¹⁸F-FDG uptake that was more intense compared to liver uptake on ¹⁸F-FDG PET studies and referred to colonoscopy were enrolled in the study.

Results:

Fifty two patients (83.8%) had at least 1 corresponding lesion on colonoscopy, whereas in 10 patients no lesion was detected. Subsequent histopathological examinations revealed no corresponding lesion in 13 (13.7%), a benign lesion in 18 (18.9%), hyperplastic polyp in 10 (10.5%), low-grade polyp in 16 (16.8%), high-grade polyp in 29 (30.5%) and malignant lesion in 9 (9.5%) of the focal ¹⁸F-FDG uptake sites. According to histopathology results, statistically no significant difference was found between the SUV_max measurements of malignant and benign cases (p>0.05) but the average SUV_max measurements of malignant cases were found to be significantly higher than lower + high-grade cases (p<0.05) and hyperplastic polyp cases (p<0.01).

Conclusion:

In conclusion, any unexpected focal ¹⁸F-FDG uptake in ¹⁸F-FDG PET/CT studies is suspicious for malignancy and should be clarified by colonoscopy. The intensity of ¹⁸F-FDG uptake does not preclude the application of colonoscopy and histopathological verification of the lesion if there is any.

Diagnostic performance of 18 F-FDG-PET/CT in inflammation of unknown origin: A clinical series of 317 patients

BACKGROUND

Inflammation of unknown origin (IUO) is a challenging situation in internal medicine.

OBJECTIVES

To describe the final diagnoses in IUO and assess the helpfulness of ¹⁸ F-fluorodesoxyglucose positron emission tomography with computerized tomography (¹⁸ F-FDG-PET/CT) in the diagnosis strategy.

RESULTS

A total of 317 IUO patients with ¹⁸ F-FDG-PET/CT were enrolled. A diagnosis was reached in 228 patients: noninfectious inflammatory diseases (NIID) (37.5%), infectious diseases (18.6%), malignancies (7.9%), and non-systemic-inflammatory miscellaneous diseases (7.9%). The two leading causes of NIID were polymyalgia rheumatica and giant cell arteritis. ¹⁸ F-FDG-PET/CT results were classified as true positive in 49.8% of patients and contributory in 75.1% of overall IUO patients (after the complete investigation set and a prolonged follow-up). In multivariate analysis, only C-reactive protein minimum level (≥50 mg/L) was associated with the contributory status of ¹⁸ F-FDG-PET/CT.

CONCLUSION

Within the wide spectrum of IUO underlying diseases, ¹⁸ F-FDG-PET/CT is helpful to make a diagnosis and to eliminate inflammatory diseases. Obese patients constitute a specific group needing further studies.

Increased Colonic Fluorodeoxyglucose Uptake in Melanosis Coli-A Case Series of Three Patients

We report 3 Japanese cases with increased colonic 18-fluorodeoxyglucose (FDG) uptake in association with melanosis coli. Case 1: A 56-year-old woman received 18-FDG positron emission tomography (PET) for comprehensive medical checkup. Case 2: A 79-year-old man received FDG-PET for follow-up evaluation for intestinal cancer. Case 3: A 51-year-old woman received FDG-PET for medical checkup. Each showed increased cecal and/or ascending colonic uptake without any colonic wall changes. Colonoscopy detected melanosis coli where FDG uptake was demonstrably increased. Neither malignancy nor inflammatory response was confirmed. Succeeding follow-ups showed neither malignant nor inflammatory lesions in any of the patients.

Correlation between incidental focal colorectal FDG uptake on PET/CT and colonoscopic and histopathological results

OBJECTIVE AND AIMS

The primary aim of this study was to evaluate the correlation between incidental focal colorectal foci on fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) with colonoscopic and histopathological results. The secondary aim was to determine to what extent these findings led to a change in patient management.

MATERIALS AND METHODS

A retrospective study was performed among 5850 patients who had an FDG-PT/CT scan from July 2015 to July 2018. Among these patients, we identified patients with a PET/CT description of incidental colorectal FDG uptake, and a colonoscopy within 90 days from the PET/CT scan. PET/CT findings were compared with colonoscopy-detected lesions and eventually histopathology on a per-lesion analysis and a per-person analysis.

RESULTS

A total of 145 patients were included in the study. A total of 180 foci of colorectal FDG uptake were detected on FDG-PET/CT. Of these, 86 foci corresponded to advanced colorectal neoplasia (ACRN), positive predictive value (PPV) 47.8%; 95% CI: 40.5-55.1%). On a per-patient analysis 81 patients had a least one ACRN at colonoscopy (PPV 55.9%; 95% CI: 47.6-63.8), this group included 20 patients (13.8%) diagnosed with cancer. There was a small positive correlation between focal FDG-uptake and the finding of ACRN at the same colonic segment at colonoscopy, which was statistically significant, rho = 0.2565, p = .002. The findings changed patient management in 67 (46.2%) cases.

CONCLUSIONS

Incidental focal colorectal FDG uptake on PET/CT is associated with a high risk of ACRN and is affecting subsequent patient management. Further evaluation with colonoscopy is recommended when the patient is considered suitable for further treatment.

Staging 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Changes Treatment Recommendation in Invasive Bladder Cancer

Given the high risk of systemic relapse following initial therapy for muscle-invasive bladder cancer (MIBC), improved pretreatment staging is needed. We evaluated the incremental value of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) after standard conventional staging, in the largest cohort of MIBC patients to date. This is a retrospective analysis of 711 consecutive patients with invasive urothelial bladder cancer who underwent staging contrast-enhanced CT (chest and abdomen) and FDG-PET/CT in a tertiary referral center between 2011 and 2020. We recorded the clinical stage before and after FDG-PET/CT and treatment recommendation based on the stage before and after FDG-PET/CT. Clinical stage changed after FDG-PET/CT in 184/711 (26%) patients. Consequently, the recommended treatment strategy based on imaging changed in 127/711 (18%) patients. In 65/711 (9.1%) patients, potential curative treatment changed to palliative treatment because of the detection of distant metastases by FDG-PET/CT. Fifty (7.0%) patients were selected for neoadjuvant/induction chemotherapy based on FDG-PET/CT. Moreover, FDG-PET/CT detected lesions suspicious for second primary tumors in 15%; a second primary malignancy was confirmed in 28/711 (3.9%), leading to treatment change in ten (1.4%) patients. Contrarily 57/711 (8.1%) had false positive secondary findings. In conclusion, FDG-PET/CT provides important incremental staging information, which potentially influences clinical management in 18% of MIBC patients, but leads to false positive results as well. PATIENT SUMMARY: In this report, we investigated the impact of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scanning on treatment of bladder cancer patients. We found that FDG-PET/CT potentially influences the treatment of almost one-fifth of patients. We therefore suggest performing FDG-PET/CT as part of bladder cancer staging.

PET/CT Integrated With CT Colonography in Preoperative Obstructive Colorectal Cancer by Incomplete Optical Colonoscopy: A Prospective Study

AIM

The aim of this study was to evaluate if integrating whole-body PET/CT with CT colonography (PET/CTC) improves the preoperative diagnosis of obstructive colorectal cancer (CRC).

METHODS

We prospectively included 47 consecutive patients (18 women and 29 men; mean age, 71 ± 14 years) suspected of having CRC by optical colonoscopy, which was not completed due to obstructive masses. To perform PET/CTC, a small caliber Foley catheter was inserted to distend the colon with CO2 insufflations. Polyps measuring 10 mm or larger were considered as high risk of malignancy. All findings were histologically confirmed.

RESULTS

Colorectal cancer was localized in the sigmoid (n = 21), rectum (n = 7), rectosigmoid junction (n = 5), ascending (n = 7), descending (n = 5), and transverse (n = 2) colon. All tumors showed FDG uptake (mean ± SD SUVmax, 20.02 ± 9.9) including one synchronic tumor (SUVmax, 10.46). Forty-seven polyps were histologically confirmed as smaller than 10 mm (n = 35) and 10 mm or larger (n = 12). All 12 polyps 10 mm or larger showed FDG uptake (SUVmax range, 3.08-19.5), but only one smaller than 10 mm could be identified by PET. Pathological lymph nodes were diagnosed in 17/47 cases after surgical removal with a sensitivity and specificity for CTC and PET/CTC of 71% and 97% and 59% and 100%, respectively. Liver metastases were confirmed in 9 patients and in 4/9 along with lung metastases (n = 2) or implants (n = 2), showing a sensitivity and specificity for CTC of 89% and 100% and both 100% for PET/CTC.

CONCLUSIONS

PET/CTC is a reliable technique for staging CRC and diagnosing synchronous tumors. In this series, PET/CTC was not able to identify small polyps but showed potential use for ruling out 10 mm or larger polyps at high risk of malignancy.

Diagnostic accuracy of F-18 FDG PET/CT for characterization of colorectal focal FDG uptake: a systematic review and meta-analysis

INTRODUCTION

We aimed to explore the role of the diagnostic accuracy of F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) for characterization of incidental colorectal focal FDG uptake through a systematic review and meta-analysis.

METHODS

The MEDLINE, EMBASE, and Cochrane Library database, from the earliest available date of indexing through April 30, 2018, were searched for studies evaluating the diagnostic performance of F-18 FDG PET/CT for characterization of incidental colorectal focal FDG uptake. We determined the sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR-), and constructed summary receiver operating characteristic curves.

RESULTS

Across 8 studies (1451 patients), the pooled sensitivity for F-18 FDG PET/CT was 0.87 (95% CI 0.82-0.90) without heterogeneity (χ² = 10.84, p = 0.37) and a pooled specificity of 0.83 (95% CI 0.76-0.89) with heterogeneity (χ² = 130.1, p = 0.00). Likelihood ratio (LR) syntheses gave an overall positive likelihood ratio (LR+) of 5.2 (95% CI 3.6-7.4) and negative likelihood ratio (LR-) of 0.16 (95% CI 0.12-0.22). The pooled DOR was 32 (95% CI 20-51).

CONCLUSION

F-18 FDG PET/CT demonstrated good sensitivity and specificity for characterization of incidental colorectal focal FDG uptake. At present, the literature regarding the use of F-18 FDG PET/CT for characterization of incidental colorectal focal FDG uptake remains still limited; thus, further large multicenter studies would be necessary to substantiate the diagnostic accuracy of F-18 FDG PET/CT for characterization of incidental colorectal focal FDG uptake.

Efficacy of 18-fluoro deoxy glucose-positron emission tomography computed tomography for the detection of colonic neoplasia proximal to obstructing colorectal cancer

Identification of secondary colonic neoplasia proximal to obstructing colorectal cancer is essential for determining the range of colorectal resection.We examined the accuracy of 18-fluoro deoxy glucose-positron emission tomography (FDG-PET) for detection of colonic neoplasia.We recruited patients with obstructing colorectal cancer from our registry. Preoperative FDG-PET was performed, and the detection rate for colonic neoplasia was estimated. Preoperative colonoscopy or postoperative colonoscopy within a year after operation was employed as the indexed standard.Ninety-three patients were included in this study. Colonic neoplasia proximal to obstruction was confirmed in 83 cases. The sensitivity and positive predictive value of FDG-PET were 25.3% and 77.8%, respectively. The sensitivity was higher in larger lesions (3.2% for <5 mm, 29.4% for 6-10 mm, 45.5% for 11-20 mm, and 71.4% for >21 mm) and in higher pathological grade lesions (14.6% for low-grade adenoma, 38.5% for high-grade adenoma, 66.7% for carcinoma in situ, and 100% for invasive carcinoma). The round shape in PET images was a predictor for neoplasia, with an area under the curve of 0.75293 at an aspect ratio of 1.70.FDG-PET should be used as a screening modality for invasive colorectal cancer (CRC) proximal to obstructing colorectal cancer.

Incidental colorectal FDG uptake on PET/CT scan and lesions observed during subsequent colonoscopy: a systematic review

BACKGROUND

Incidental colorectal fluorodeoxyglucose (FDG) uptake can be observed during a positron emission tomography/computed tomography (PET/CT) scan. For clinical and/or histological assessment of the cause, a colonoscopy is then performed. A systematic review was conducted to investigate the relationship between incidental colorectal FDG uptake and lesions observed during a subsequent colonoscopy.

METHODS

A literature search was conducted using PubMed, Embase, and Web of Science with the keywords concerning PET/CT scan and colonoscopy. The studies were selected using inclusion criteria defined a priori and were described individually to examine the correlation between incidental colorectal FDG uptake and the lesions found at colonoscopy.

RESULTS

Twenty-six of 1606 studies found were included. In total, 108,578 patients underwent an FDG-PET/CT scan as part of a diagnostic work-up or cancer staging. In total, 2546 incidental colorectal FDG uptakes were described in 2121 patients (mean age 62.7 years SD ± 5.1), of which 2045 uptakes in 1635 patients were examined by colonoscopy, within a mean of 37 days (SD ± 28). The colonoscopic lesions included neoplasms (n = 1097; 322 cancers), benign lesions (n = 273), and inflammatory lesions (n = 71). Colonoscopies were normal in 604 patients. In total, 82% of lesions were located in the same location as the FDG uptakes. The positive predictive value was 70% (95% CI [68-72]).

CONCLUSIONS

Incidental colorectal FDG uptake, as evaluated by subsequent colonoscopy, often reveals neoplastic lesions. Predominantly, lesions were located at the same location as FDG uptake. Further investigation is warranted before recommending that incidental colorectal FDG uptake should always result in referral to diagnostic colonoscopy.

Clinicopathological analysis and risk factors of advanced colorectal neoplasms incidentally detected by 18F-FDG PET-CT

BACKGROUND

As the clinical use of fluorine-18-fluorodeoxyglucose PET-computed tomography (F-FDG PET-CT) has increased, the incidental finding of F-FDG uptake with subsequent diagnosis of advanced neoplasm at colorectum has increased. The aim of this study is to analyze the characteristics and risk factors of advanced colorectal neoplasm incidentally detected by F-FDG PET-CT.

PATIENTS AND METHODS

Patients who underwent colonoscopy because of an incidental finding of F-FDG uptake at the colorectum from January 2006 to January 2015 at Yeungnam University Hospital were reviewed retrospectively. Advanced neoplasm was defined as adenoma of at least 10 mm, adenoma with serrated or villous component, high-grade dysplasia, and adenocarcinoma.

RESULTS

Of the 19 798 candidates, 180 patients with incidental colorectal F-FDG uptake were included in this study. The indications of PET-CT were metastasis work-up, health screening, and others. The male to female ratio was 1.6 : 1 and the mean age was 62.7±11.4 years. A total of 156 lesions were detected in the colorectum and 86 (47.8%) were diagnosed as advanced neoplasms. Of the 86 patients with advanced neoplasms, 34 (39.5%) underwent an operation, 34 (39.5%) underwent endoscopic resection, and 18 (20.9%) underwent chemotherapy or conservative treatments. In univariate analysis, age of 62.5 years or older, carcinoembryonic antigen (CEA) of at least 3.4 ng/ml, maximum standardized uptake value (SUVmax) of at least 8.0, hypertension, F-FDG uptake on the rectosigmoid, and PET-CT for metastasis work-up showed a significant association with advanced neoplasm. In multivariate analysis, CEA (P=0.028), SUVmax (P<0.001) and an indication of PET-CT for metastasis work-up (P=0.008) were independent predictors of advanced neoplasm.

CONCLUSION

Colonoscopy should be recommended in case of F-FDG uptake at the colorectum, particularly in patients with CEA of at least 3.4 ng/ml, SUVmax of at least 8.0, or metastasis work-up of malignancy.

Detection of incidental colorectal pathology on positron emission tomography/computed tomography

BACKGROUND

Positron emission tomography/computed tomography (PET/CT) is an important modality in cancer imaging. With its increasing availability and use, it is not uncommon to detect incidental focal colorectal ¹⁸ F-FDG uptake which poses a diagnostic challenge, as they may be associated with malignant or pre-malignant colorectal lesions. The aim of our study is to determine the proportion of these findings which represents true pathology.

METHODS

Patients with incidental focal colorectal ¹⁸ F-FDG uptake on PET/CT who subsequently underwent colonoscopy between January 2002 to September 2013 were identified from a prospective database in a tertiary referral centre. PET/CT results were correlated with colonoscopy and pathology results in these patients. Positive predictive values (PPVs) and 95% confidence intervals (CIs) of PET/CT in the detection of incidental colorectal pathology were calculated.

RESULTS

A total of 148 patients (92 men and 56 women), with a mean age 73 years (range of 36 to 93 years) were included in the study. A total of 170 foci of colorectal ¹⁸ F-FDG uptake were detected on PET/CT. Of these, 101 foci corresponded to a malignant or pre-malignant lesion (PPV 59%; 95% CI: 52-67%). On a per-patient analysis, 93 patients had at least one focus of colorectal ¹⁸ F-FDG uptake which corresponded to a pre-malignant or malignant lesion (PPV 63%; 95% CI: 54-71%).

CONCLUSION

Focal colorectal ¹⁸ F-FDG uptake on PET/CT is associated with a significant proportion of malignant or pre-malignant lesions. Further evaluation with colonoscopy is recommended.

Circulating cell-free nucleic acids as biomarkers in colorectal cancer screening and diagnosis

Screening methods for the most frequent diagnosed malignant tumor, colorectal cancer (CRC), have limitations. Circulating cell-free DNA (cfDNA) analysis came into focus as a potential screening test for CRC. Detection of epigenetic and genetic alterations of cfDNA as DNA methylation or DNA mutations and related ribonucleic acids may improve cancer detection based on unique, CRC-specific patterns. In this review the authors summarize the CRC-specific nucleic acid biomarkers measured in peripheral blood and their potential as screening markers. Detection of DNA mutation has inadequate sensitivity; however, methylated DNA can be established with higher sensitivity from CRC plasma samples. The ribonucleic acid based miRNA studies represented higher sensitivity for CRC as compared with mRNA studies. Recently, isolation of cfDNA has become automated, highly reproducible and a high throughput method. With automated possible diagnostic tools, a new approach may be available for CRC screening as liquid biopsy.