Incidental colonic 18F-fluorodeoxyglucose uptake: do we need colonoscopy for patients with focal uptake confined to the left-sided colon?

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.

Assessment of water enema PET/CT: an effective imaging technique for the diagnosis of incidental colorectal 18F-FDG uptake

BACKGROUND

To validate the feasibility of water enema PET/CT (WE-PET/CT) in incidental colorectal 18F-FDG uptake and improve the accuracy of diagnosing colorectal neoplastic lesions.

METHODS

We retrospectively analysed the electronic records of 338 patients undergoing common PET/CT and WE-PET/CT at our hospital. PET/CT results were correlated with colonoscopy pathology and follow-up results. The ROC contrast curve was plotted to evaluate the accuracy of SUVmax on common PET/CT and WE-PET/CT for detecting neoplastic lesions. SUVmax and the median retention indexes (RIs) of cancerous, precancerous, and benign lesions and physiologic uptake were compared.

RESULTS

The sensitivity, specificity and accuracy of diagnosing neoplastic lesions with common PET/CT were 84.0%, 78.3% and 80.2%, respectively. The corresponding results with WE-PET/CT were 95.8%, 96.5% and 96.2%. The AUC of SUVmax on WE-PET/CT was significantly higher than that on common PET/CT (0.935 vs. 0.524, p < 0.001). The median SUVmax on WE-PET/CT was significantly higher than that on common PET/CT in cancerous and precancerous lesions, and significantly decreased in benign lesions and physiologic uptake (p < 0.001). The RI was significantly different between cancerous lesions and physiologic uptake, between precancerous lesions and physiologic uptake, between benign lesions and physiologic uptake, and between cancerous and benign lesions (p < 0.05).

CONCLUSIONS

WE-PET/CT is a noninvasive, well-tolerated and effective technique for diagnosing incidental colorectal 18F-FDG uptake. It is helpful for a timely colonoscopy and can effectively avoid an unnecessary colonoscopy for incidental colorectal 18F-FDG uptake.

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.

Clinically significant findings in patients with focal incidental colorectal abnormalities on positron emission tomography-CT scans

INTRODUCTION

The aim of this study was to determine the clinical significance of focal incidentally detected colorectal abnormalities on ¹⁸ F- Fluoro-2-Deoxy-D-Glucose (FDG) PET-CT scans.

METHODS

Retrospective audit of PET-CT scans performed at our institution between 2009 and 2014. Demographic and clinical details were retrieved from electronic patient records. An advanced adenoma was defined as: ≥1 cm in size, tubullo-villous histology, or displaying high grade dysplasia. A high-risk lesion (HRL) was defined as an advanced adenoma or colorectal cancer (CRC).

RESULTS

Of the 1911 PET-CT eligible scans, focal incidental colorectal FDG uptake was detected in 99 (5.2%) patients. Colonoscopy was undertaken in 43 (43.4%) patients and 45 FDG-avid sites were evaluated. The commonest site of abnormal FDG uptake was the rectosigmoid region, with 34 (75.6%) of the 45 foci being located in this area. Overall, 23 (53.5%) of these patients had clinically significant pathology. Of the 45 focal PET-CT abnormalities evaluated, 17 (37.8%) were adenomas, of which 11 (24.4%) were advanced adenomas, and six (13.3%) were cancers, with a total of 17 (37.8%) HRLs. Five of the six patients with CRC underwent surgical resection, whilst one had endoscopic resection. The overall survival for the entire cohort was 18 months (range 1-72 months) with those that underwent colonoscopy having higher overall survival compared to those that did not (38 vs. 13.5 months).

CONCLUSION

Incidental colorectal abnormalities on PET-CT scans are often clinically significant. However, careful selection for colonoscopy is important due to the poor survival in these patients related to the underlying primary malignancy.

Potential clinical value of quantitative fluorine-18-fluorodeoxyglucose-PET/computed tomography using a graph-based method analysis in evaluation of incidental lesions of gastrointestinal tract: correlation with endoscopic and histopathological findings

OBJECTIVES

To identify the clinical relevance of incidentally detected lesions (IDLs) in the gastrointestinal tract (GIT) with 18F-FDG PET/CT and to assess the potential benefit of using semiquantitative PET measures to discern malignant from benign lesions.

METHODS

Forty-one patients who underwent F-FDG PET/CT scans during the oncologic follow-up, revealing abnormal incidental 18F-FDG accumulations in the GIT were included in this retrospective analysis. Incidental PET/CT findings were correlated with endoscopic and histological findings. Semiquantitative PET values (SUVmax, SUVmean, SULpeak, and TLG) were evaluated by using a new graph-based method. Two sample t-test analysis has been performed to evaluate the differences of PET parameters between precancerous or cancerous lesions and inflammatory disease.

RESULTS

Nine of the 41 patients had an IDL of the GIT on F-FDG PET/CT (detection rate 22%). Endoscopic examination and biopsy have confirmed the presence of precancerous or cancerous lesions as follow: colonic adenoma with high-grade dysplasia (N = 2), colonic adenoma with low-grade dysplasia (N =3), colonic metastatic lesion from primary breast cancer (N =1), gastric carcinoma (N=3). Precancerous or cancerous lesions showed a higher SUVmax, SUVmean, SULpeak, and TLG with a mean value of 10.6 (range, 5.3- 16.7), 6.2 (range, 2.1-10.6), 5.2 (2.7-11), and 66.6 (range, 7.4-164), than patients with inflammatory and endoscopically negative lesions. Two sample t-test analysis showed that SUVmean (P = 0.03), SULpeak (P = 0.05) were statistically different between the two subgroups.

CONCLUSION

The use of new semiquantitative PET parameters may increase the diagnostic yield of FDG PET in the case of abnormal incidental F-FDG accumulations.

Intraoperative colonoscopy in laparoscopic colorectal surgery: A review of recent publications

INTRODUCTION

Laparoscopic colorectal resection is becoming the gold standard for treating colorectal cancers because it offers superior short-term and comparable long-time outcomes compared to open surgery. Intraoperative colonoscopy (IOC) is increasingly performed for tumor localization and mucosal assessment. The aim of this report was to review the safety and efficacy of IOC in laparoscopic colorectal surgery.

METHOD

A MEDLINE search of studies of IOC in laparoscopic colorectal surgery was performed. We focused on three aspects of IOC use: (i) IOC for intraoperative tumor localization; (ii) colonic irrigation and IOC for obstructive left-sided colorectal cancers; and (iii) IOC for assessing colorectal anastomosis.

RESULTS

During laparoscopic colorectal surgery, IOC enables accurate localization of early mucosal tumors, detection of lesions in the proximal unexamined colon for obstructive left-sided cancer, and visual assessment of anastomosis. Additionally, IOC allows for proper surgical resection, management of concomitant lesions, immediate maintenance of hemostasis, suture repair of leaks, and the creation of a protective stoma as necessary.

CONCLUSIONS

Intraoperative colonoscopy is beneficial in laparoscopic colorectal surgery. Experienced surgical endoscopists should be trained to safely perform IOC.

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.

Incidental detection of colorectal lesions by FDG PET/CT scans in melanoma patients

BACKGROUND

Increased use of PET/CT scans in oncology patients has raised detection of Colorectal incidentalomas (CIs). The frequency and diagnostic outcomes of identifying these lesions in melanoma patients have not previously been studied. This studies primary objective was to determine the prevalence of CIs found on PET/CT scans in melanoma patients. The secondary objectives were to correlate the PET/CT findings with the pathology found at colonoscopy, and identify which patients were referred for colonoscopy.

METHODS

A retrospective analysis of patients identified from the prospectively collected research database of Melanoma Institute Australia. 2509 patients with melanoma underwent PET/CT scans between 2001 and 2013. The prevalence of CIs, the correlation of lesions, and the survival of patients who underwent colonoscopy versus patients who did not were analyzed.

RESULTS

The prevalence of CIs in melanoma patients who had PET/CT scans was 3.2%. Forty-five of the 81 (56%) patients with CIs underwent colonoscopy. Of these, premalignant or malignant disease was found in 58%. Patients with previous metastatic melanoma were significantly less likely to be referred for colonoscopy. Patients undergoing colonoscopy had significantly better survival, as did those without previous distant metastases before the CIs were found, and those without any metastases at the time the CIs were found. These factors were not significant on multivariate analysis.

CONCLUSION

The prevalence of incidental colorectal lesions identified on PET/CT scans in melanoma patients was found to be equivalent to that in the general cancer population. Patients undergoing colonoscopy had better survival than those who did not.

Incidental colorectal focal 18 F-FDG uptake: a novel indication for colonoscopy

BACKGROUND AND STUDY AIMS

 The relevance of incidental colorectal focal ¹⁸ F-FDG PET/CT uptake is debatable. All patients who were referred for colonoscopy because of incidental colonic focal FDG uptake were included in this retrospective study.

PATIENTS AND METHODS

 PET/CT imaging characteristics were reviewed by a nuclear physician who was blinded to endoscopic and histopathological findings to determine the location of FDG uptake sites and to measure the maximum standardized uptake values (SUVmax) and metabolic volume (MV). Endoscopic findings were categorized as malignant lesions (ML), high-risk polyps (HRP), low-risk polyps (LRP) or other non-neoplastic lesions (NNL).

RESULTS

 Seventy patients with 84 foci of FDG uptake were included. The proportions of true-positive (lesions found at colonoscopy at the same location) and false-positive (no lesion at colonoscopy) PET/CT findings were 65.5 % (n = 55) and 34.5 % (n = 29). Median SUVmax values did not differ between true-positive and false-positive findings ( P  = 0.27). Median MV30 values differed significantly between true-positive (5.5 cm ³ , [3.3 - 10.9 cm ³ ]) and false-positive (9.7 cm ³ , [5.2 - 40.8 cm ³ ]) findings ( P  = 0.015). Among the 55 true-positive FDG uptake sites, there were 14 (25.5 %) malignant lesions, 30 (54.5 %) HRP, 4 (7.3 %) LRP, and 7 (12.7 %) NNL. Median MV30 values differed significantly between advanced neoplasia (5.0 cm ³ , [2.9 - 9.7 cm ³ ]) and other endoscopic findings (9.4 cm ³ , [5.2 - 39.8 cm ³ ]) ( P  = 0.001); the AUROC was 0.71. By per-colonic segment analysis, the distribution of true-positive, false-negative, false-positive, and true-negative FDG PET/CT findings was as follows: 21.5 %, 14.2 %, 11.5 %, and 52.8 %, respectively.

CONCLUSION

 Our study demonstrates that follow-up complete colonoscopy is mandatory in all patients with incidental colorectal focal ¹⁸ F-FDG PET/CT uptake.

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.

Characteristics and outcomes of endoscopically resected colorectal cancers that arose from sessile serrated adenomas and traditional serrated adenomas

Background/Aims

The efficacy and safety of endoscopic resection of colorectal cancer derived from sessile serrated adenomas or traditional serrated adenomas are still unknown. The aims of this study were to verify the characteristics and outcomes of endoscopically resected early colorectal cancers developed from serrated polyps.

Methods

Among patients who received endoscopic resection of early colorectal cancers from 2008 to 2011, cancers with documented pre-existing lesions were included. They were classified as adenoma, sessile serrated adenoma, or traditional serrated adenoma according to the baseline lesions. Clinical characteristics, pathologic diagnosis, and outcomes were reviewed.

Results

Overall, 208 colorectal cancers detected from 198 patients were included: 198 with adenoma, five with sessile serrated adenoma, and five with traditional serrated adenoma. The sessile serrated adenoma group had a higher prevalence of high-grade dysplasia (40.0% vs. 25.8%, P<0.001) than the adenoma group. During follow-up, local recurrence did not occur after endoscopic resection of early colorectal cancers developed from serrated polyps. In contrast, two cases of metachronous recurrence were detected within a short follow-up period.

Conclusions

Cautious observation and early endoscopic resection are recommended when colorectal cancer from serrated polyp is suspected. Colorectal cancers from serrated polyp can be treated successfully with endoscopy.

Incidental gastrointestinal 18F-Fluorodeoxyglucose uptake associated with lung cancer

BACKGROUND

F-Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is increasingly used for the initial staging and restaging of lung cancer. Incidental gastrointestinal findings are often observed on (18)F-FDG PET/CT. The objective of this study was to assess incidental 18F-FDG uptake by the gastrointestinal tract (GIT) in patients with lung cancer.

METHODS

Two hundred thirty consecutive 18F-FDG PET/CT examinations performed for lung cancer over a 3-year period were retrospectively reviewed for the presence of incidental FDG uptake in the GIT. The charts of patients with positive FDG uptake were then reviewed and analysed to determine the GIT uptake sites, the standardized uptake value (SUV) max and the final clinical diagnosis.

RESULTS

Fifty-two patients (52/230, 23%) demonstrated incidental FDG uptake in the GIT. Thirty-three patients (63.5%) had diffuse uptake (oesophagus, n = 2, colon, n = 31) and 19 patients (36.5%) had focal uptake (oesophagus, n = 1, small bowel, n = 1, ascending colon, n = 5, descending colon, n = 4, sigmoid, n = 4, rectum, n = 3, and anal margin, n = 1). Twelve of the 52 patients with GIT uptake were further investigated, revealing, a diagnosis of malignancy in 4 patients with focal FDG uptake. No significant differences in mean SUVmax were observed between patients with malignant and benign GIT diseases.

CONCLUSION

This study demonstrates a high incidence of FDG uptake in the GIT associated with lung cancer. Focal GIT uptake was frequently associated with malignant disease. These results suggest that further GIT investigations should be performed in patients with focal GIT uptake.

Colonoscopic Findings in Patients With Incidental Colonic Focal FDG Uptake

OBJECTIVE

The purpose of this study was to investigate the nature of FDG-avid and non-FDG-avid lesions detected at colonoscopy in patients presenting with incidental focal colonic FDG uptake at PET/CT.

MATERIALS AND METHODS

Among 9073 patients who underwent PET/CT over a 4-year period, 82 patients without a history of colonic disease had focal colonic FDG uptake and underwent colonoscopy. In consensus, a radiologist and a nuclear physician read images from these PET/CT examinations. They recorded the location of focal FDG uptake in the colon and associated CT abnormalities and measured maximum standardized uptake value (SUVmax) and metabolic volume (MV). Readings were performed twice--first without and second with knowledge of lesion location at colonoscopy. The final diagnosis was based on colonoscopic findings and histopathologic results categorized into benign, premalignant, or malignant.

RESULTS

One hundred seven foci of colonic FDG uptake at PET/CT and 150 lesions at colonoscopy were detected. Among 107 foci of FDG uptake, 65 (61%) corresponded to a lesion at colonoscopy (true-positive findings), and 42 (39%) did not (false-positive findings). Among 150 lesions found at colonoscopy, 85 (57%) were not FDG avid (false-negative findings). The MV of true-positive findings was lower than that of false-positive findings (4.0 ± 0.4 cm(3) vs 6.2 ± 0.7 cm(3); p = 0.006), but SUVmax did not differ (7.4 ± 0.5 vs 7.7 ± 0.5; p = 0.649). Considering the histopathologic categories of the lesions and the false-positive findings, there was no difference in SUVmax (p = 0.103), but MV was lower in premalignant lesions than in false-positive findings (p = 0.005).

CONCLUSION

Focal colonic FDG uptake may indicate the presence of a benign, pre-malignant, or malignant lesion. Subsequent colonoscopy should not be restricted to the colonic site of FDG uptake.

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

Focal (18)F-fluorodeoxyglucose (FDG) colonic activity can be incidentally seen in positron emission tomography/computed tomography (PET/CT) scans. Its clinical significance is still unclear. The purpose of this study was to assess the significance of focal FDG activity in PET/CT scans by correlating the imaging findings to colonoscopy results, and come up with some guidelines for recommendation of follow-up colonoscopy. A total of 133 patients who underwent both (18)F-FDG PET/CT for different oncological indications and colonoscopy within 3 months were retrospectively studied. Imaging, colonoscopy and pathology results were analyzed. Of the 133 FDG-PET/CT scans, 109/133 (82%) did not show focal colonic FDG activity, and 24/133 (18%) did. Of the 109/133 PET/CTs without focal colonic FDG activity, 109/109 (100%) did not have evidence of colon cancer after colonoscopy and histology. Of the 24/133 PET/CTs with focal colonic FDG activity, 10/24 (42%) had pathologic confirmation of colon cancer and 14/24 (58%) did not have evidence of colon cancer after colonoscopy and histological analysis. Sensitivity was 10/10 (100%), specificity 109/123 (89%), positive predictive value (PPV) 10/24 (42%) and negative predictive value (NPV) 109/109 (100%). Incidental focal (18)FDG activity in PET/CT imaging shows a high sensitivity, specificity and NPV for malignancy, with a not so high PPV of 42%. Although some people would argue that a 42% chance of malignancy justifies colonoscopy, this maybe is not possible in all cases. However, the high sensitivity of the test does not allow these studies to be overlooked. We provide our recommendations as per when to send patients with focal FDG colonic activity to have further characterization with colonoscopy.