Detection of incidental colorectal tumours with 18F-labelled 2-fluoro-2-deoxyglucose positron emission tomography/computed tomography scans: results of a prospective study

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.

The Clinical Significance of Incidental GIT Uptake on PET/CT: Radiologic, Endoscopic, and Pathologic Correlation

Incidental gastrointestinal tract (GIT) [18F]-Fluorodeoxyglucose (FDG) uptake in positron emission technology/computed tomography (PET/CT) is an unexpected and often complicated finding for clinicians. This retrospective study reviewed 8991 charts of patients who underwent PET/CT: 440 patients had incidental GIT uptake, of which 80 underwent endoscopy. Patient characteristics, imaging parameters, and endoscopic findings were studied. Of the 80 patients, 31 had cancer/pre-cancer lesions (16 carcinomas; 15 pre-malignant polyps). Compared to patients with benign/absent lesions, patients with cancer/pre-cancer lesions were significantly older (p = 0.01), underwent PET/CT for primary evaluation/staging of cancer (p = 0.03), had focal GIT uptake (p = 0.04), and had lower GIT uptake (p = 0.004). Among patients with focal uptake, an SUVmax of 9.2 had the highest sensitivity (0.76) and specificity (0.885) in detecting cancer/pre-cancerous lesions. Lower GIT uptake was most common in the sigmoid colon, and upper GIT uptake was most frequent in the stomach. In a bivariate analysis, predictors of cancer/pre-cancer were older age, PET/CT indicated for primary evaluation, focal uptake, uptake in the lower GIT, and higher SUVmax. Further endoscopic investigation is warranted for patients with incidental GIT uptake, especially in the elderly or those presenting for primary evaluation with PET/CT, with the following findings on imaging: lower GIT uptake, focal uptake, or high SUVmax.

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.

Radiologic Imaging Modalities for Colorectal Cancer

BACKGROUND

Studies reported various diagnostic value of radiologic imaging modalities for diagnosis and management of colorectal cancer (CRC).

AIMS

To summary the diagnosis and management of CRC using computed tomography colonography (CTC), magnetic resonance colonography (MRC), and positron emission tomography (PET)/computed tomography (CT).

METHODS

Comprehensive literature searches were conducted in PubMed, EmBase, and the Cochrane library for studies published before April 2021. The diagnostic performance of CTC, MRC, and PET/CT for CRC was summarized.

RESULTS

A total of 54 studies (17 studies for CTC, 8 studies for MRC, and 29 studies for PET/CT) were selected for final analysis. The sensitivity and specificity for CTC ranged from 27 to 100%, 88 to 100%, respectively, and the pooled sensitivity and specificity for CTC were 0.97 (95% CI 0.88-0.99) and 0.99 (95% CI 0.99-1.00). The sensitivity and specificity for MRC ranged from 48 to 100%, 60 to 100%, respectively, and the pooled sensitivity and specificity for MRC were 0.98 (95% C: 0.77-1.00) and 0.94 (95% CI 0.84-0.98). The sensitivity and specificity for PET/CT ranged from 84 to 100%, 33 to 100%, respectively, and the pooled sensitivity and specificity for PET/CT were 0.94 (95% CI 0.92-0.96) and 0.94 (95% CI 0.90-0.97). The area under the receiver operating characteristic curve for CTC, MRC, and PET/CT was 1.00 (95% CI 0.99-1.00), 0.99 (95% CI 0.98-1.00), and 0.97 (0.95% CI 0.95-0.98), respectively.

CONCLUSIONS

This study suggested both CTC and MRC with relative higher diagnostic value for diagnosing CRC, while PET/CT with higher diagnostic value in detecting local recurrence for patients with CRC.

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.

Assessment of incidental focal colorectal uptake by analysis of fluorine-18 fluorodeoxyglucose positron emission tomography parameters

BACKGROUND

Colon and rectal cancers are among the top five cancers worldwide in terms of their incidence and mortality rates. As the treatment options for cure include surgery even in specific advanced-stage cases, the early detection of lesions is important for applying active treatment methods. Fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) is an established imaging study for many types of cancers; however, physiologic uptake in the gastrointestinal tract is a frequent finding and may interfere with lesion identification. Nevertheless, as unexpectedly observed focal colorectal F-18 FDG uptake may harbor malignant lesions, further examination must not be avoided.

AIM

To assess the clinical implications of unexpected focal colorectal F-18 FDG uptake by analyzing FDG PET parameters.

METHODS

A total of 15143 F-18 FDG PET/CT scans performed at our hospital between January 2016 and September 2021 were retrospectively reviewed to identify incidentally observed focal colorectal FDG uptake. Finally, 83 regions showing focal colorectal FDG uptake with final histopathological reports from 80 patients (45 men and 35 women with mean ages of 66.9 ± 10.7 years and 63.7 ± 15.3 years, respectively) were eligible for inclusion in the present study. Each focal hypermetabolic colorectal region was classified as malignant, premalignant, or benign according to the histopathological report. PET parameters such as maximum and peak standardized uptake value (SUVmax and SUVpeak), metabolic tumor volume (MTV), mean SUV of the metabolic tumor volume (mSUVmtv), and total lesion glycolysis (TLG) were measured or calculated for the corresponding hypermetabolic regions. Parametric and non-parametric statistical comparisons of these parameters were performed among the three groups. Receiver operating characteristic curves were plotted to identify cut-off values.

RESULTS

The detection rate of incidental focal colorectal uptake was 0.53% (80/15,143). Of the 83 regions with unexpected focal colorectal hypermetabolism, 28.9% (24/83) were malignant, 32.5% (27/83) were premalignant, and 38.6% (32/83) were benign. Overall, 61.4% of the regions had malignant or premalignant lesions. SUVmax, SUVpeak, and mSUVmtv differentiated malignant and/or premalignant lesions from benign lesions with statistical significance (P < 0.05). mSUVmtv3.5 differentiated malignant from benign lesions, with the largest area under the curve (AUC) of 0.792 and a cut-off of 4.9. SUVmax showed the largest AUC of 0.758 with a cut-off value of 7.5 for distinguishing between premalignant and benign lesions. Overall, SUVmax with a cut-off value of 7.6 (AUC: 0.770, 95% confidence interval (CI): 0.668-0.872; sensitivity, 0.686; specificity, 0.688) was a superior parameter for distinguishing between malignant/premalignant and benign lesions or physiologic uptake. No parameters differentiated malignant from premalignant lesions. Moderate or weak positive correlations were observed between the long diameter of the malignant lesions and PET parameters such as SUVpeak and some mSUVmtv.

CONCLUSION

Approximately two-thirds (61.4%) of incidental focal hypermetabolic colorectal regions were malignant/premalignant lesions, for which SUVmax was an independent diagnostic parameter. Unexpected suspicious focal colorectal FDG uptake should not be avoided and consideration for further evaluation is strongly recommended not to miss the two-thirds.

Rectal operative bed: ?tumor? post-management changes … positron emission tomography/computed tomography (PET/CT) can answer

Background

Rectal cancer is a common malignancy that continues to have a highly variable outcome. Local pelvic recurrence following surgery is usually leading to incurable disease. Surgical resection with stage-appropriate combined-modality therapy is the mainstay in the treatment of rectal cancer. A difficulty has been reported in distinguishing the benign post-management findings from tumor recurrence. By adding the metabolic changes to the post-operative morphologic changes, combined positron emission tomography (PET) and computed tomography (CT) may offer clinically useful addition in operative bed evaluation.

Results

The study included 30 patients, 17 males (56.6%) and 13 females (43.3%). Suspicious operative bed findings included pre-sacral soft tissue density noted in 20 patients (66%), anastomotic site mural thickening in five patients (16.6%), and post-operative loco-regional nodes in five patients (16.6%). Moreover, pre-sacral soft tissue focal avid uptake was noted in 17 patients (17/20, 85%), and no uptake noted in three patients (3/20, 15%). Anastomotic site mural thickening was seen in five patients with positive uptake noted in three patients (3/5, 60%), and no uptake seen in two patients (2/5, 40%). Loco-regional nodes were seen in five patients with positive uptake in five patients. The most accurate SUV max cut-off value among studied cases was 3.5. Confirmation of PET/CT results was done by histopathological assessment in ten patients (33.3%) and by follow up after 6 months in 20 patients (66.6%) with recurrence noted in 15 patients (75%) and normal post-operative findings noted in five patients (25%).

Conclusion

PET/CT study is an effective tool for evaluation of suspicious colorectal oncologic operative bed findings noted in the routine CT studies. PET/CT fusion images affect the clinical management by guiding further procedures (surgery and radiation therapy).

Incidental 18F-FDG uptake in the colon: value of contrast-enhanced CT correlation with colonoscopic findings

OBJECTIVES

To evaluate the impact of morphological information derived from contrast-enhanced CT in the characterization of incidental focal colonic uptake in ¹⁸F-FDG PET/CT examinations.

METHODS

A total of 125 patients (female: n = 53, male: n = 72) that underwent colonoscopy secondary to contrast-enhanced, full-dose PET/CT without special bowel preparation were included in this retrospective study. PET/CT examinations were assessed for focal colonic tracer uptake in comparison with the background. Focal tracer uptake was correlated with morphological changes of the colonic wall in the contrast-enhanced CT images. Colonoscopy reports were evaluated for benign, inflammatory, polypoid, precancerous, and cancerous lesions verified by histopathology, serving as a reference standard. Sensitivity, specificity, PPV, NPV, and accuracy for detection of therapeutic relevant findings were calculated for (a) sole focal tracer uptake and (b) focal tracer uptake with correlating CT findings in contrast-enhanced CT.

RESULTS

In 38.4% (48/125) of the patients, a focal ¹⁸F-FDG uptake was observed within 67 lesions. Malignant lesions were endoscopically and histopathologically diagnosed in eleven patients, and nine of these were detected by focal ¹⁸F-FDG uptake. A total of 34 lesions with impact on short- or long-term patient management (either being pre- or malignant) were detected. Sensitivity, Specificity, PPV, NPV, and accuracy for sole ¹⁸F-FDG uptake for this combined group were 54%, 69%, 29%, 85%, and 65%. Corresponding results for focal ¹⁸F-FDG uptake with correlating CT findings were 38%, 90%, 50%, 86%, and 80%. This resulted in a statistically significant difference for diagnostic accuracy (p = 0.0001) CONCLUSION: By analyzing additional morphological changes in contrast-enhanced CT imaging, the specificity of focal colonic ¹⁸F-FDG uptake for precancerous and cancerous lesions can be increased but leads to a considerate loss of sensitivity. Therefore, every focal colonic uptake should be followed up by colonoscopy.

Clinical-endoscopic relevance of incidental colorectal lesions detected by PET-CT

AIM

to determine the proportion of incidental colon lesions detected by PET-CT and their correlation with the endoscopic and histological findings. In addition, to determine the maximum standardized uptake value (SUVmax) that can discriminate between benign and malignant lesions in our series of cases.

METHODS

this was a retrospective study of 3,000 patients evaluated by PET-CT for staging or response to treatment of primary neoplasms, between 2011 and 2015. Patients with incidental uptake in the colon were included in the study. Exclusion criteria included an incomplete, poorly prepared or abandoned colonoscopy, inflammatory bowel disease and treatment with metformin.

RESULTS

the study cohort comprised 71 patients evaluated by PET-CT and subsequently analyzed by endoscopy; 69% were male with a mean age of 65.77 ± 11.2. The rate of incidental colon lesions found by PET-CT was 1.73%, with 52 incidental colonic uptakes reported in 50 patients. The location of the uptake was the rectum (19.23%), sigmoid colon (34.62%), descending colon (13.46%), transverse colon (1.9%), ascending colon (19.23%), cecum (9.62%) and ileocolic anastomosis (1.92%). Thirty-five pathological colonoscopies (71.15%) were identified: the findings included five neoplasms (13.51%), two inflammatory lesions (5.4%) and 30 adenomatous polyps (81.1%). Significant differences were found between neoplastic SUVmax (11.7 g/ml; p = 0.03) and polyps (9.26 g/ml; p = 0.04) in relation to inflammatory lesions and normal endoscopies (6.05 g/ml). There were no differences in terms of the size of the polyps, nor the presence or absence of high grade dysplasia (p = 0.12 and 0.33). Both PET-CT and endoscopy proved consistent for locating lesions (k 0.90; CI 95% 0.86-0.93).

CONCLUSION

there is a good correlation between the findings identified by PET-CT and the endoscopic study. In our study, a SUVmax > 11 g/ml suggests a malignant pathology, which aids the prioritization of an endoscopic study.

PET/CT incidental detection of second tumor in patients investigated for pancreatic neoplasms

BACKGROUND

Positron Emission Tomography/computed tomography (PET/CT) is an imaging technique which has a role in the detection and staging malignancies (both in first diagnosis and follow-up). The finding of an unexpected region of FDG (Fluorodeoxyglucose) uptake can occur when performing whole-body FDG-PET, raising the possibility of a second primary tumor. The aim of this study was to evaluate our experience of second primary cancer incidentally discovered during PET/CT examination performed for pancreatic diseases, during the initial work-up or follow-up after surgical resection.

METHODS

In this study, a retrospective evaluation of a prospectively collected data base was performed. Three hundred ninety- nine patients with pancreatic pathology were evaluated by whole body PET/CT imaging from January 2004 to December 2014. Among them, 348 patients were scanned before surgical resection and 51 during the course of their follow-up (pancreatic cancer). Median follow-up time was 29 months (range 14-124).

RESULTS

Fifty-six patients (14%) had incidental uptake of FDG in their organs: 31 patients had focal uptake and 25 showed diffuse with or without focal uptake. All patients with focal uptake were investigated, and invasive malignancy was diagnosed in 22 patients: 14 colon, 4 lung, 1 larynx, 1 urothelial, 1 breast cancer, and 1 colon metastasis from pancreatic cancer. Twenty patients underwent resection, and 6 endoscopic removal of colonic polyps. Three patients were not operated for advanced disease, and two patients did not show any pathology (PET/CT false positive). Of the 10 patients investigated for diffuse uptake, no malignancy was found; none of these patients developed a second cancer during the follow-up.

CONCLUSIONS

As in other malignancies, unexpected FDG uptake can occur in patients having PET/CT investigation for pancreatic diseases. Focal uptake is likely to be a malignancy and deserves further investigations, although the stage and the poor prognosis of primary pancreatic cancer should be kept in mind. Some selected patients may benefit from the aggressive treatment of incidental lesions and show survival benefit.

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.

Limited Identification of Dual-time-point Positron Emission Tomography/Computed Tomography in Advanced Colorectal Neoplasms

Objective We investigated whether dual-time-point 18-Fluorodeoxyglucose (¹⁸FDG) positron emission tomography/computed tomography (PET/CT) could improve the positive predictive value for detecting advanced colorectal neoplasms (cancer, adenoma ≥10 mm or adenoma with high-grade dysplasia). Methods We retrospectively searched for consecutive patients with a known primary cancer, who had a colonic ¹⁸FDG uptake incidentally found by PET/CT, followed by colonoscopy between January 2013 and August 2014. The clinical characteristics including the maximum standardized uptake value (SUVmax) were compared between advanced colorectal neoplasms and non-advanced lesions. Results Forty-eight patients had 51 foci with an incidental focal colorectal uptake of ¹⁸FDG. Among these 51 foci, 28 foci were judged as being advanced neoplasms, whereas 23 foci identified as non-advanced lesions. Four cases were missed by PET/CT: two laterally spreading tumors (LSTs) with intramucosal cancer and two severe adenomas (<10 mm). The positive predictive value for the detection of advanced neoplasms was 55%. The per-spot performance of PET/CT showed that SUVmax was significantly higher in advanced neoplasms than in non-advanced lesions for the early-phase (10.1±4.9 vs. 6.5±3.2, p=0.029) and the delayed-phase (12.0±6.0 vs. 7.4±4.0, p=0.022). However, more importantly, there was a significant overlap of the SUVmax and no significant difference was found in the retention index (19.2±20.1 vs. 16.6±29.4, p=0.767). Conclusion Dual-time-point PET/CT was found to have limited impact for identifying advanced colorectal neoplasms in spite of its high sensitivity and it might therefore not be able to identify either LSTs or small advanced neoplasms.

Clinical significance of incidental [18 F]FDG uptake in the gastrointestinal tract on PET/CT imaging: a retrospective cohort study

Background

The frequency and clinically important characteristics of incidental (18)F-fluorodeoxyglucose ([18 F]FDG) positron emission tomography (PET) uptake in the gastrointestinal tract (GIT) on PET/CT imaging in adults remain elusive.

Methods

All PET/CT reports from 1/1/2000 to 12/31/2009 at a single tertiary referral center were reviewed; clinical information was obtained from cases with incidental (18)F-FDG uptake in the GIT, with follow-up through October, 2012.

Results

Of the 41,538 PET/CT scans performed during the study period, 303 (0.7 %) had incidental GIT uptake. The most common indication for the PET/CT order was cancer staging (226 cases, 75 %), with 74 % for solid and 26 % for hematologic malignancies. Of those with solid malignancy, only 51 (17 %) had known metastatic disease. The most common site of GIT uptake was the colon, and of the 240 cases with colonic uptake, the most common areas of uptake were cecum (n = 65), sigmoid (n = 60), and ascending colon (n = 50). Investigations were pursued for the GIT uptake in 147 cases (49 %), whereas 51 % did not undergo additional studies, largely due to advanced disease. There were 73 premalignant colonic lesions diagnosed in 56 cases (tubular adenoma, n = 36; tubulovillous adenoma with low grade dysplasia, n = 27; sessile serrated adenoma, n = 4; tubulovillous adenoma with high grade dysplasia, n = 3; villous adenoma, n = 3), and 20 cases with newly diagnosed primary colon cancer. All 20 (100 %) patients with malignant colonic lesions had a focal pattern of [18 F]FDG uptake. Among cases with a known pattern of [18 F]FDG uptake, 98 % of those with premalignant lesions had focal [18 F]FDG uptake. Eighteen (90 %) of the cases with newly diagnosed colon cancer were not known to have metastatic disease of their primary tumor. Areas of incidental uptake in the ascending colon had the greatest chance (42 %) of being malignant and premalignant lesions than in any other area.

Conclusion

Focality of uptake is highly sensitive for malignant and premalignant lesions of the GIT. In patients without metastatic disease, incidental focal [18]FDG uptake in the GIT on PET/CT imaging warrants further evaluation.

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.

Retrospektive Analyse von Zufallsbefunden, die bei Patienten mit kutanem malignen Malignom durch (18) F-Fluordeoxyglucose-PET/CT erhoben wurden

HINTERGRUND UND ZIELE

Bei der (18) F-Fluordeoxyglucose-Positronenemissionstomographie/Computertomographie (FDG-PET/CT) ergeben sich häufig Zufallsbefunde. In der vorliegenden Studie konzentrierten wir uns auf mittels FDG-PET/CT erhaltene Zufallsbefunde bei Patienten mit kutanem Melanom und überprüften deren Relevanz hinsichtlich weiterer diagnostischer Maßnahmen und Interventionen.

PATIENTEN UND METHODEN

Die Krankenakten von 181 konsekutiven Melanom-Patienten wurden retrospektiv ausgewertet, um das Management von Zufallsbefunden zu dokumentieren. Der Schwerpunkt lag dabei auf den histologischen Befunden.

ERGEBNISSE

Bei 33 von 181 (18 %) Patienten lagen 39 relevante Zufallsbefunde vor, und zwar im Kolorektalbereich (n = 15 Patienten), in der Schilddrüse (n = 8), der Prostata (n = 2), dem Bewegungsapparat (n = 2), in Lymphknoten (n = 2), der Parotis (n = 1), den Mandeln (n = 1), den Nieren (n = 1) und der Gallenblase (n = 1). Bei 25 Patienten schlossen sich weitere diagnostische Verfahren an, wobei in 21 Fällen ein klinisches Korrelat nachgewiesen wurde. Bei 16 von 21 Patienten ergab sich eine Neoplasie, darunter fünf maligne Läsionen (vier Kolonkarzinome und ein Prostatakarzinom). Die Malignome wurden frühzeitig diagnostiziert und in der Mehrzahl der Fälle erfolgreich entfernt.

SCHLUSSFOLGERUNGEN

Der Einsatz der FDG-PET/CT als Routine-Diagnostik wird in den Leitlinien empfohlen und ist indiziert bei malignem Melanom ab Stadium IIC. In dieser Studie wurden auf effektive Weise ansonsten nicht erkannte Krebserkrankungen, insbesondere Kolonkarzinome, detektiert. In den meisten Fällen war eine frühe Intervention möglich. Zufallsbefunde durch FDG-PET/CT sollten, unter Berücksichtigung des Zustands und der Wünsche des Patienten, mit den geeigneten diagnostischen Maßnahmen abgeklärt werden.

What approach should we take for the incidental finding of increased 18F-FDG uptake foci in the colon on PET/CT?

INTRODUCTION

F-Fluorodeoxyglucose (F-FDG) PET/CT represents an imaging modality that is gaining increasingly more prominence in screening, staging, and therapeutic monitoring of malignant diseases. An incidental focus of uptake in different regions of the body is not an uncommon finding during PET/CT imaging. Patients with incidental gastrointestinal tract findings comprise ∼3% of the overall patient group. The aim of the current study was to provide contributory information in relation to the answer on the most appropriate approach in cases with incidental colonic F-FDG uptake.

PATIENTS AND METHODS

A retrospective examination was performed on PET/CT results of 5258 patients. Of these, 152 were recommended to undergo colonoscopy because of the presence of suspicious foci and 31 underwent colonoscopy within 60 days with biopsy from all visible lesions. These dates were also examined.

RESULTS

Of the 24 patients undergoing colonoscopy with a suspicion of malignancy, five (20.83%) had no pathological findings. Of the 19 (79.17%) cases with a pathological finding in endoscopy, histopathology showed a benign lesion in five (20.83%), premalignant lesion in seven (29.17%), and a malignant lesion in seven (29.17%). Among seven patients undergoing colonoscopy because of a suspicion of inflammatory bowel disease, five were free of pathological signs and two patients with pathological endoscopy findings had nonspecific inflammation as documented by histopathological examination.

CONCLUSION

Colonoscopic and histopathological examination of the increased foci of colonic F-FDG uptake incidentally detected at PET/CT seems to be a plausible approach.

Correlation of Ki-67 proliferation index and 18-fluorodeoxyglucose uptake in colorectal incidental lesions detected by positron emission tomography-computed tomography

BACKGROUND/AIM

To investigate whether focal high maximum standardized uptake value (SUVmax) determined by 18-fluorodeoxyglucose (FDG) positron emission tomography (PET)-computed tomography (CT) imaging is correlated with proliferation index in the colorectal region.

MATERIALS AND METHODS

SUVmax values of 31 colorectal neoplasms that were incidentally detected during PET-CT examination were compared to dysplasia degree, histopathologic diagnosis, and immunohistochemical expression of the Ki-67 proliferation marker.

RESULTS

Statistically significant correlations were found between SUVmax and Ki-67 proliferation index, dysplasia degree, and histopathologic diagnosis. Median SUVmax value was found to be significantly higher in high-risk lesions than low-risk lesions.

CONCLUSION

The Ki-67 proliferation index is an indicator of SUVmax in colorectal tract. SUVmax values can predict malignancy and prognosis in this region. Colonoscopy and biopsy should always be performed whenever a focal high FDG uptake is determined incidentally in a patient.

Personalized Clinical Decision Making in Gastrointestinal Malignancies: The Role of PET

Gastrointestinal malignancies comprise a heterogeneous group of diseases that include both common and rare diseases with very different presentations and prognoses. The mainstay of treatment is surgery in combination with preoperative and adjuvant chemotherapy depending on clinical presentation and initial stages. This article outlines the potential use of fluorodeoxyglucose-PET/CT in clinical decision making with special regard to preoperative evaluation and response assessment in gastric cancer (including the gastroesophageal junction), pancreatic cancer (excluding neuroendocrine tumors), colorectal cancer, and gastrointestinal stromal tumors.

Focal colorectal uptake in (18)FDG-PET/CT: maximum standard uptake value as a trigger in a semi-automated screening setting

BACKGROUND

Focal colorectal uptake in (18)FDG-PET/CT may be associated with a malignancy and can be quantified. This provides the basis for an automatic trigger threshold above which cases are flagged for colonoscopic evaluation and below which for individual assessment.

PURPOSE

To determine the lowest maximum standard uptake (SUVmax) in colorectal cancer that could be used as a threshold to trigger endoscopic evaluation and to evaluate whether the SUVmax needs to be further normalised to a priori known extrinsic factors.

METHODS

The SUVmax was measured in 54 colorectal carcinomas and correlated with gender, age, blood glucose level, injected activity, body mass index and time to scan using t test or correlation coefficients (Pearson or Spearman, according to distribution).

RESULTS

There was no correlation between SUVmax and any of the extrinsic factors mentioned above. The lowest SUVmax value was 5 [mean ± SD (range): 11.1 ± 4.8 (5.0-24.6)].

CONCLUSION

In contrast to most other screening techniques, semi-automation in colorectal screening seems possible with PET/CT. This opens the door for further study into the feasibility of automated screening. Independent from extrinsic factors, an SUVmax ≥5.0 in a focal colorectal uptake in (18)FDG-PET/CT should automatically trigger for endoscopic evaluation, if not contraindicated. Cases with SUVmax <5 should be assessed individually before referral for endoscopy. Thus, more interpretation time could be spent on those cases with a lower uptake and more ambiguous diagnosis.

The preoperative SUVmax for (18)F-FDG uptake predicts survival in patients with colorectal cancer

Background

The study was to investigate whether ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake, analyzed by positron emission tomography (PET), can be used preoperatively to predict survival in Chinese patients with colorectal carcinoma.

Methods

A prospectively maintained colorectal cancer database was retrospectively reviewed between June 2009 and December 2011. All included patients had been newly diagnosed with colorectal cancer (of various stages) and evaluated by ¹⁸F-FDG-PET/computed tomography (CT) within the 2 weeks preceding surgery. Univariate and multivariate analyses were used to determine whether the maximal standardized uptake value (SUVmax) and various clinicopathological and immunohistochemical factors were correlated with survival. Receiver operating characteristics (ROC) curve and Kaplan-Meier survival curve analyses were used to explore whether SUVmax could predict survival in these patients.

Results

A total of 107 patients were enrolled in the study (mean age, 59.26 ± 12.66 years; 66.35 % males), with 77 surviving to the end of follow-up (average 60 months). Univariate analysis indicated that tumor size, TNM stage, nodal metastasis, the ratio of metastasized nodes to retrieved nodes, cyclin D1 immunostaining and SUVmax correlated with survival (P < 0.05). Multivariate analysis showed that only TNM stage and SUVmax were associated with survival (P < 0.05). ROC curve analysis determined the optimal SUVmax cutoff for predicting survival to be 11.85 (sensitivity, 73.3 %; specificity, 75.3 %). Survival was significantly longer in patients with preoperative SUVmax ≤11.85 (P < 0.001, log-rank test).

Conclusions

SUVmax, measured by ¹⁸F-FDG-PET/CT, provides a useful preoperative prognostic factor for patients with colorectal cancer.

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.

Incidental colonic focal FDG uptake on PET/CT: can the maximum standardized uptake value (SUVmax) guide us in the timing of colonoscopy?

PURPOSE

In patients undergoing (18)F-FDG PET/CT, incidental colonic focal lesions can be indicative of inflammatory, premalignant or malignant lesions. The maximum standardized uptake value (SUVmax) of these lesions, representing the FDG uptake intensity, might be helpful in differentiating malignant from benign lesions, and thereby be helpful in determining the urgency of colonoscopy. The aim of our study was to assess the incidence and underlying pathology of incidental PET-positive colonic lesions in a large cohort of patients, and to determine the usefulness of the SUVmax in differentiating benign from malignant pathology.

METHODS

The electronic records of all patients who underwent FDG PET/CT from January 2010 to March 2013 in our hospital were retrospectively reviewed. The main indications for PET/CT were: characterization of an indeterminate mass on radiological imaging, suspicion or staging of malignancy, and suspicion of inflammation. In patients with incidental focal FDG uptake in the large bowel, data regarding subsequent colonoscopy were retrieved, if performed within 120 days. The final diagnosis was defined using colonoscopy findings, combined with additional histopathological assessment of the lesion, if applicable.

RESULTS

Of 7,318 patients analysed, 359 (5 %) had 404 foci of unexpected colonic FDG uptake. In 242 of these 404 lesions (60 %), colonoscopy follow-up data were available. Final diagnoses were: adenocarcinoma in 25 (10 %), adenoma in 90 (37 %), and benign in 127 (53 %). The median [IQR] SUVmax was significantly higher in adenocarcinoma (16.6 [12 - 20.8]) than in benign lesions (8.2 [5.9 - 10.1]; p < 0.0001), non-advanced adenoma (8.3 [6.1 - 10.5]; p < 0.0001) and advanced adenoma (9.7 [7.2 - 12.6]; p < 0.001). The receiver operating characteristic curve of SUVmax for malignant versus nonmalignant lesions had an area under the curve of 0.868 (SD ± 0.038), the optimal cut-off value being 11.4 (sensitivity 80 %, specificity 82 %, positive predictive value 34 %, negative predictive value 98 %).

CONCLUSION

In these patients with incidental colonic focal activity undergoing PET/CT (the largest series published to date), malignancies had significantly higher SUVmax values than all other types of lesions. However, SUVmax could not distinguish between benign lesions and adenomas. In conclusion, all incidental findings in the colon should be further evaluated and lesions with SUVmax ≥11.4 should be evaluated without delay.

[18F]Fluorodeoxyglucose PET/Computed Tomography in Gastrointestinal Malignancies

This article discusses the current state-of-the-art application of 2-deoxy-2-[(18)F]fluoro-d-glucose (FDG)-PET and FDG-PET/computed tomography (CT) in the management of patients with gastrointestinal malignancies. Gastrointestinal malignancies include many different cell types, several common malignancies of which may be imaged by FDG-PET/CT. This review focuses on gastric carcinoma, pancreatic carcinoma, hepatocellular carcinoma, cholangiocarcinoma, colorectal carcinoma, and stroma cell tumors. The role of FDG-PET/CT in staging these malignancies is discussed, in addition to (re)staging, detection of recurrent disease, patient selection/prognostication, and response assessment, using the currently available literature.

Prevalence and malignancy risk of focal colorectal incidental uptake detected by (18)F-FDG-PET or PET/CT: a meta-analysis

Background

The aim of the study was to meta-analyze published data about prevalence and malignancy risk of focal colorectal incidentalomas (FCIs) detected by Fluorine-18-Fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography (¹⁸F-FDG-PET or PET/CT).

Methods

A comprehensive computer literature search of studies published through July 31^st 2012 regarding FCIs detected by ¹⁸F-FDG-PET or PET/CT was performed. Pooled prevalence of patients with FCIs and risk of malignant or premalignant FCIs after colonoscopy or histopathology verification were calculated. Furthermore, separate calculations for geographic areas were performed. Finally, average standardized uptake values (SUV) in malignant, premalignant and benign FCIs were reported.

Results

Thirty-two studies comprising 89,061 patients evaluated by ¹⁸F-FDG-PET or PET/CT were included. The pooled prevalence of FCIs detected by ¹⁸F-FDG-PET or PET/CT was 3.6% (95% confidence interval [95% CI]: 2.6–4.7%). Overall, 1,044 FCIs detected by ¹⁸F-FDG-PET or PET/CT underwent colonoscopy or histopathology evaluation. Pooled risk of malignant or premalignant lesions was 68% (95% CI: 60–75%). Risk of malignant and premalignant FCIs in Asia-Oceania was lower compared to that of Europe and America. A significant overlap in average SUV was found between malignant, premalignant and benign FCIs.

Conclusions

FCIs are observed in a not negligible number of patients who undergo ¹⁸F-FDG-PET or PET/CT studies with a high risk of malignant or premalignant lesions. SUV is not reliable as a tool to differentiate between malignant, premalignant and benign FCIs. Further investigation is warranted whenever FCIs are detected by ¹⁸F-FDG-PET or PET/CT.

Correlation between incidental FDG PET/CT colorectal observations and endoscopic and histopathological results

Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is used in the imaging workup of various malignancies. Incidental gastrointestinal observations on FDG PET/CT may be of clinical significance. The aim of the present study was to evaluate endoscopic and histopathological observations in patients referred for colonoscopy due to incidental FDG colonic uptake on a PET/CT study. Fifty-six patients with incidental colonic findings on FDG PET/CT underwent colonoscopy. Normal colonoscopies were observed in 63% of the patients. In 37% of the colonoscopies, we identified an endoscopic observation, including 67% with benign adenomatous polyps, 3% with hyperplastic polyps, 20% with advanced histological lesions and 10% with a malignancy.

A comparison of positron emission tomography and colonoscopy for the detection of advanced colorectal neoplasms in subjects undergoing a health check-up

Background & Aims

There is no agreement as to whether F-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) screening for advanced colorectal neoplasms is meaningful. This retrospective study was undertaken to determine whether FDG PET/CT may be a valuable screening tool for the detection of advanced colorectal neoplasms.

Methods

A retrospective review of the records of 1,109 FDG PET/CT scans acquired from January 2007 to December 2011 was performed. Colonoscopy and FDG PET/CT imaging were performed within two days of each other. The results of colonoscopy were taken as the gold standard, either with or without the results of the histopathological examination. An advanced neoplasm was defined as the presence of a malignant tumor, an adenoma ≥1 cm, or histological evidence of high-grade dysplasia or significant villous components.

Results

A total of 36 subjects had advanced colorectal neoplasms detected by colonoscopy (totaling 38 neoplasms). Six of the 38 neoplasms were also detected by FDG PET/CT. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of FDG PET/CT in the detection of advanced colorectal neoplasms were 15.8% (6/38), 99.1% (1063/1073), 37.5% (6/16), 97.1% (1063/1095), and 96.2% (1069/1111) respectively. The presence of lesions with an endoscopic size ≤1.5 cm (P<0.001) and low-grade dysplasia (P<0.001) were the main predictors of false-negative FDG PET/CT findings.

Conclusions

We conclude that FDG PET/CT screening of advanced colorectal neoplasms is unwarranted, especially in the presence of lesions with an endoscopic size ≤1.5 cm or low-grade dysplasia.

Etiology and significance of incidentally detected focal colonic uptake on FDG PET/CT

BACKGROUND

Incidental colonic uptake of 18F-flurodeoxyglucose (FDG) is not an infrequent finding encountered during whole body positron emission tomography (PET) imaging. Almost all studies on this topic are in Western populations, which have a markedly different epidemiological profile for colorectal premalignant and malignant conditions as compared to that of the Indian subcontinent.

AIM

The purpose of this study was to assess the etiology of incidentally detected focal FDG uptake in the colon by comparing it with colonoscopy and histopathology.

MATERIALS AND METHODS

Electronic medical records of patients who underwent FDG PET/computed tomography (CT) at our institution for a 2½-year period from January 2009 to July 2011 were reviewed. There were 32 out of 9000 (0.35%) patients whose PET/CT reports mentioned incidental focal colonic FDG uptake, of which 24 patients subsequently underwent colonoscopy. Lesions which appeared neoplastic on colonoscopy were confirmed with histopathology obtained after biopsy or surgery. Colonoscopy and pathology findings were considered as gold standard.

RESULTS

Among the 24 patients who underwent a colonoscopy, 3 patients had normal findings (12.5%). A positive colonoscopy was noted in 21 patients (87.5%) with the lesion coinciding with the location described in the PET/CT report. Adenomatous polyps were detected in 12 patients (37.5%), whereas in 8 patients (25%) malignant lesions were confirmed [adenocarcinoma n = 5, non-Hodgkin's lymphoma (NHL) n = 2, malignant melanoma n = 1]. In one patient, colonic uptake was diagnosed as inflammatory. The mean standardized uptake valuemax (SUVmax) for the 12 premalignant lesions was 16.9 ± 9.6 (range 7.5-37.4) and the mean SUVmax for the 8 malignant lesions was 12.9 ± 5.5 (range 6.7-21.6). The difference in SUVmax between the premalignant adenomatous polyps and the malignant lesions was not statistically significant (P = 0.316).

CONCLUSIONS

Our study shows that a significant proportion of patients (62.5%, 20/32) showing an incidental focal FDG uptake will harbor premalignant (adenomatous polyps) or malignant lesions, and further evaluation with colonoscopy and biopsy is warranted in such cases.

Incidental focal colorectal 18F-fluorodeoxyglucose uptake on positron emission tomography/computed tomography

AIM: To assess the clinical significance of incidental focal colorectal ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake on ¹⁸F-FDG-positron emission tomography/computed tomography (PET/CT).

METHODS: The records of all the cases which had undergone colonoscopy after PET/CT within a two weeks interval were reviewed. Adenomas were considered advanced when they were villous, ≥ 10 mm in size, or had high-grade dysplasia. Colorectal cancers and advanced adenomas are collectively referred to as advanced colorectal neoplasms. Receiver-operating characteristic curve analysis was used to determine the significant predictive maximum standardized uptake value (SUVmax) cutoff value for advanced colorectal neoplasms and cancer.

RESULTS: Ninety-five colorectal lesions matched the site of incidental focal colorectal ¹⁸F-FDG uptake on PET/CT and 146 did not. Colonoscopy showed advanced colorectal neoplasms corresponding to the site of ¹⁸F-FDG uptake in 49 of the 95 (51.5%) lesions with incidental uptake. Of the lesions without incidental uptake, only 6 of 146 (4.1%) had advanced colorectal neoplasms on colonoscopy, indicating a statistically significant difference between the two groups (P < 0.001). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of incidental focal ¹⁸F-FDG uptake in identifying advanced colorectal neoplasms were 89.1%, 75.3%, 51.6%, 95.9%, and 78.4%, respectively. In detecting only CRC, these values were 89.2%, 69.6%, 34.7%, 97.3%, and 72.6%, respectively. The significant SUVmax cutoff value for advanced colorectal neoplasms (area under the curve 0.755, P < 0.001) was 4.35, with a sensitivity, specificity, PPV, NPV, and accuracy of 75.5%, 65.2%, 69.8%, 71.4% and 70.5%, respectively. For CRC, 5.05 was the significant SUVmax cutoff value (area under the curve 0.817, P < 0.001), with a sensitivity, specificity, PPV, NPV, and accuracy of 84.8%, 71.0%, 80.9%, 89.8%, and 75.8%, respectively.

CONCLUSION: The presence of incidental focal colorectal ¹⁸F-FDG uptake on PET/CT with a SUVmax ≥ 4.35 increases the likelihood of an advanced colorectal neoplasm.

The use and importance of liposomes in positron emission tomography

Among different imaging modalities, Positron Emission Tomography (PET) gained importance in routine hospital practice depending on ability to diagnose diseases in early stages and tracing of therapy by obtaining metabolic information. The combination of PET with Computed Tomography (CT) forms hybrid imaging modality that gives chance to obtain better images having higher resolution by fusing both functional and anatomical images in the same imaging modality at the same time. Therefore, better contrast agents are essentially needed. The advance in research about developing drug delivery systems as specific nanosized targeted systems gained an additional importance for obtaining better diagnosis and therapy of different diseases. Liposomes appear to be more attractive drug delivery systems in delivering either drugs or imaging ligands to target tissue or organ of diseases with higher accumulation by producing in nano-scale, long circulating by stealth effect and specific targeting by modifying with specific ligands or markers. The combination of positron emitting radionuclides with liposomes are commonly in research level nowadays and there is no commercially available liposome formulation for PET imaging. However by conjugating positron emitter radionuclide with liposomes can form promising diagnostic agents for improved diagnosis and following up treatments by increasing image signal/contrast in the target tissue in lower concentrations by specific targeting as the most important advantage of liposomes. More accurate and earlier diagnosis of several diseases can be obtained even in molecular level with the use of stable and effectively radiolabeled molecular target specific nano sized liposomes with longer half-lived positron emitting radionuclides.