Management of patients following detection of unsuspected colon lesions by PET imaging

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.

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.

Incidental detection of colorectal lesions on 18 F-FDG-PET/CT is associated with high proportion of malignancy: A study in 549 patients

Background and study aims  Further diagnostics of incidental colorectal lesions on ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is questionable. Therefore, we aimed to evaluate the clinical importance of incidentally detected colorectal lesions on FDG-PET/CT. Patients and methods  In the North Denmark Region, a retrospective study was performed among 19,987 patients who had an FDG-PET/CT from January 2006 to December 2015. Among these patients, we identified patients with a colonoscopy within 12 months from the PET/CT scan and a description of incidental colorectal PET-avid lesions on the PET/CT. PET findings were compared with colonoscopy-detected lesions and eventually histopathology. Results  Incidental PET-avid lesions were observed in 549 patients. Colonoscopy revealed lesions in 457 (83 %), among whom 338 patients had a final histopathological diagnosis. Malignant and premalignant lesions were found in 297 patients (54 % among patients with a PET-avid lesion). The lesions were cancer in 76 patients and adenoma in 221 patients of whom 30 had high-grade and 191 low-grade adenomas. The findings changed patient management in 166 cases (30 % of all patients with a PET-avid lesion). A colonoscopy-based surveillance program was initiated for 80 % of patients with high-grade adenoma. No patients with PET-avid lesions but normal colonoscopy developed colorectal cancer during 3 years of observation (median observation time 7 years). Conclusions  Incidental colorectal FDG uptake was infrequently observed, but when present, it was associated with a high rate of malignant or premalignant lesions. Our results indicate that patients with incidental colorectal FDG uptake should be referred to diagnostic work-up including 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.

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.

Can positron emission tomography detect colorectal adenomas and cancers?

BACKGROUND AND AIM

Fluorine-18 2-fluoro-2-deoxy-d-glucose positron emission tomography (PET) is effective and less invasive than other modalities used to diagnose tumors, including colorectal cancer (CRC). However, the detectability of adenomas and CRCs, especially in the early stages, is unclear.

METHODS

We evaluated the records of 2323 consecutive eligible patients who underwent both a total colonoscopy (TCS) and PET between October 2002 and September 2012 at a tertiary cancer center. The PET findings were verified by TCS performed independently within 1 year. Target lesions were defined as CRCs and adenomas that were 6 mm or larger in size.

RESULTS

Total colonoscopy detected 532 target lesions ≥ 6 mm in size: 56 T2-T4 CRCs, 39 T1 CRCs, 223 advanced adenomas, and 214 low-grade adenomas. Of the 532 lesions, 216 (40.6%) were PET positive. Of the 369 cases with positive uptakes, PET detected target lesions in the matched segments for 58.5% (216/369). Sensitivity of PET to T2-T4 CRCs, T1 CRCs, advanced adenomas, and low-grade adenomas was 92.9%, 79.5%, 50.7%, and 9.3%, respectively. PET could detect 76.5% (13/17) of T1 CRCs whose size is 10 to 19 mm and 85.0% (17/20) of T1 CRCs equal or larger than 20 mm. The multivariate analysis excluding T2-T4 CRCs showed malignant histology, larger size, protruded lesions, villous histology, and lesions in distal colon were significant factors.

CONCLUSIONS

Sensitivity of PET for detecting T2-T4 and even T1 cancers are promising. However, sensitivity of PET to adenomas, even advanced adenomas, is limited.

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.

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.

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.

Optimizing the role of FDG PET-CT for potentially operable metastatic colorectal cancer

Recent treatment advances now allow a realistic chance of cure in selected patients with metastatic colorectal carcinoma (CRC). Accurate pre-treatment staging is crucial to ensure appropriate management by identification of patients with more advanced disease who will not benefit from surgery. (18)Fluorine 2-fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography (PET-CT) has a firmly established role in staging, restaging, and recurrence detection of a range of tumors. This article will review the role of PET-CT in patients with CRC with a particular emphasis on optimizing the technique in patients with potentially operable metastatic disease.

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

BACKGROUND/AIMS

Although access to [18F]2-fluoro-2-deoxyglucose (18F-FDG) positron emission tomography and computed axial tomography (PET/CT) for patients with malignancy has increased, little information is available on the suitability of PET/CT for diagnosis of advanced colonic neoplasms in oncology patients and on the clinical significance of incidental 18F-FDG focal uptake confined to the left-sided colon.

METHODS

Patients who underwent 18F-FDG PET/CT followed, within 90 days, by colonoscopy were identified. Case-control analysis was undertaken to determine whether focal 18F-FDG uptake confined to the left-sided colon was associated with advanced neoplasms in the right-sided colon.

RESULTS

One hundred ninety-five patients with colonic 18F-FDG uptake and 561 without colonic (18)F-FDG uptake were identified. Of the 195 patients with focal colonic 18F-FDG activity, 103 patients (52.8%) had 145 advanced colonic neoplasms, including 58 colon cancers and 11 metastatic cancers. In the detection of advanced colonic neoplasms, the sensitivity, specificity, positive predictive value, and negative predictive value of PET/CT were 54.4, 82.4, 46.9, and 86.3%, respectively. Overall accuracy was 76.2%. Ten (8.0%) of the 125 patients with focal 18F-FDG uptake confined to the left-sided colon had three colon cancers and seven advanced adenomas in the right-sided colon. Case-control analysis revealed that focal 18F-FDG uptake confined to the left-sided colon was associated with an advanced neoplasms in the right-sided colon (OR, 3.02; 95% CI, 1.12-8.13; P = 0.023).

CONCLUSIONS

Colonic focal (18)F-FDG uptake by oncology patients warrants endoscopic verification. Complete colon evaluation by colonoscopy is required, even for patients with focal 18F-FDG uptake confined to the left-sided colon.

The management impact of clinically significant incidental lesions detected on staging FDG PET-CT in patients with non-small cell lung cancer (NSCLC): an analysis of 649 cases

To evaluate FDG PET-CT in the detection of unexpected pre-malignancy or second malignancy at the initial staging of patients with histologically proven non-small cell lung cancer (NSCLC) and its impact on management.

METHODS

Staging FDG PET-CT scans acquired between February 2006 and July 2010 in 649 patients (M=389; F=260) with NSCLC were reviewed for the presence of unexpected pre-malignancy or second primary. A "True-Positive" lesion represented a second primary or pre-malignant lesion. A "False-Positive" lesion was due to benign causes or an atypical site of metastasis from NSCLC.

RESULTS

77 (12%) patients were identified on PET-CT as having a potential pre-malignancy or second primary. 39 out of 77 (51%) patients had diagnostic verification where histopathology served as reference standard in 33 patients (85%) and the rest had endoscopy and progress PET-CT scans. 20 patients (3.1%) had a second primary (n=11) or pre-malignant lesions comprising dysplastic colorectal polyps (n=9), and additional therapy and/or management change for the index tumour was instigated in 17 patients (85%). In patients with a second primary, 3 (27%) patients had a high impact change in management from an initial curative intent to palliative.

CONCLUSION

Staging FDG PET-CT is highly valuable in identifying second primary cancers or pre-malignant lesions in patients with NSCLC. When a second primary is detected on PET-CT, there is a high impact change in management in 27% of patients.