Performance of FDG PET/CT in postoperative colorectal cancer patients with a suspected recurrence and a normal CEA level. Nucl Med Commun. 2010;31:576-582. [PMID: 20216474 DOI: 10.1097/mnm.0b013e32833845b7]

Diagnostic Performance of F-18 FDG PET/CT in the Detection of Recurrent Colorectal Cancer: Correlation with Biochemical Markers and Conventional Imaging Modalities

Background/Objectives: Although the role of PET/CT imaging is well established in oncology, its diagnostic value in routine monitoring for recurrent colorectal cancer (CRC) is still controversial. The aim was to evaluate the diagnostic value of F-18 FDG PET/CT in detecting recurrent CRC in correlation with CEA, CA 19-9 levels, and conventional imaging modalities (CIM). Methods: Between 2009 and 2023, a retrospective study was performed including 134 CRC patients referred for PET/CT imaging on the suspicion of recurrence, based on elevated CEA and/or CA 19-9 and/or equivocal CIM findings. According to our institution's Tumor Board CRC protocol, after the initial treatment, which was dependent on the TNM stage (neoadjuvant therapy, primary resection, or adjuvant treatment), patients underwent a standard 5-year surveillance including CEA and CA 19-9 measurements, CIM, and colonoscopy, every six months. The statistics, including univariate and multivariate analyses were conducted using the IBM SPSS 20.0 statistical software. p-values < 0.05 were considered statistically significant. Results: Recurrent CRC was confirmed in 54/134 (40.3%) patients with elevated tumor markers. PET/CT showed high diagnostic performance in detecting recurrent CRC with sensitivity, specificity, PPV, NPV, and accuracy of 94.4%, 82.5%, 78.5%, 95.7%, and 87.3%, respectively. The CEA showed a high sensitivity of 98.1% but both low specificity and accuracy of 15% and 48.5%, respectively. The sensitivity, specificity, and accuracy for CA 19-9 and CIM for diagnosis of CRC recurrence were 44.4%, 67.5%, 58.2%, and 51.9%, 98.8%, 79.9%, respectively. The AUC for PET/CT, elevated CEA levels, CIM, and elevated CA 19-9 levels was 0.885 (95% CI: 0.824-0.946; p < 0.001), 0.844 (95% CI: 0.772-0.916; p < 0.001), 0.753 (95% CI: 0.612-0.844; p < 0.001), and 0.547 (95% CI: 0.442-0.652; p = 0.358), respectively. Univariate analysis showed that both PET/CT and CIM positive results were highly associated with CRC recurrence (p < 0.001 and p < 0.001, respectively). At the same time, gender, mucinous tumor type, presence of initial lymph node metastasis (N+), and presence of initial distant metastasis (M+) had no significance (p = 0.211, p = 0.158, p = 0.583, and p = 0.201, respectively). Our multivariate analysis showed that independent predictors for CRC recurrence are positive PET/CT scans (p < 0.001), positive CIM results (p = 0.001), and elevated CA 19-9 levels (p = 0.023). Although CA 19-9 was not detected as a statistically significant predictor in the univariate analysis (p = 0.358), in a multivariate analysis it was recognized as a significant predicting factor in detecting the CRC recurrence (p = 0.023). Conclusions: F-18 FDG PET/CT showed high diagnostic efficacy in CRC recurrence detection, in correlation with CEA levels, CA 19-9 levels, and CIM. This imaging modality should be routinely integrated into the post-operative follow-op in patients with elevated tumor markers.

Statistical Modeling of Relations Between PET/CT Parameters and CEA in Recurrent and Metastatic Colorectal Cancer

Background

Colorectal cancer (CRC) is a diverse disease with various clinical, pathological and molecular features that affect tumor biological behavior, treatment response and prognosis.

Objective

The aim of this study was to evaluate the correlation between metabolic 18F-FDG PET/CT parameters (SUVmax, MTV and TLG) and CEA in recurrent and metastatic CRC and to evaluate prognostic value of metabolic 18F-FDG PET/CT parameters in recurrent and metastatic CRC.

Methods

A descriptive study of 100 patients with previously detected and surgically treated CRC referred to PET/CT with a suspicion of recurrent or metastatic CRC. CEA was measured within three months from the imaging. A low-dose PET/CT was performed per institutional protocol. For each hypermetabolic lesion, metabolic PET/CT parameters (SUVmax, MTV, TLG) were calculated semiautomatically. Pathohistology or clinical data from the follow-up were used as the gold standard. Sensitivity, specificity, PPV and NPV for 18F-FDG PET/CT and CEA in detection of recurrent or metastatic CRC were calculated. Correlation between CEA and SUVmax, MTV and TLG was calculated, separately. To assess the prognostic values of metabolic parameters in CRC, survival analysis with 18-month progression-free survival (PFS) as an endpoint was performed. Microsoft Excel sheets, ROC and Kaplan-Meier curves were used to present the data. Logrank and Tarone-Ware test and Cox model of proportional hazards were used to compare the groups.

Results

Study included 100 patients, 45 males and 55 females, age range 36-81 years, mean age 61,4 years. Cancer site was colon in 56% and rectum in 44%. Sensitivity, specificity, PPV and NPV of 18F-FDG PET/CT in detection of recurrent or metastatic CRC was 95%, 73%, 70% and 95%, respectively. Sensitivity, specificity, PPV and NPV of CEA in detection of recurrent or metastatic CRC was 58%, 96%, 91% and 78%, respectively. SUVmax, MTV and TLG positively correlated with CEA, but only CEA-TLG correlation was considered significant (r=0,67). The regression model analysis revealed: SUVmax (HR=0,63, 95%CI=0,28-1,41, p=0,214), MTV (0,59, 95%CI=0,28-1,22, p=0,111) and TLG (HR=0,45 95%CI=0,21-0,99, p=0,028), and the prognostic role in CRC was proven for TLG only.

Conclusion

Metabolic 18F-FDG PET/CT parameters may have the prognostic value in CRC, but further multicentric prospective studies are required for validation.

Comparison of 18FDG-PET/CT and conventional follow-up methods in colorectal cancer: A randomised prospective study

BACKGROUND

A surveillance program was performed in colorectal cancer (CRC) patients after surgery, to diagnose asymptomatic recurrence.

AIMS

To assess whether 18-FDG positron emission tomography/CT (PET/CT) improved the detection of recurrence during a 3-year follow-up.

METHODS

A multicentre, two-arm randomised prospective trial comparing different 36-month follow-up strategies. Complete colonoscopy was performed at baseline and after 3 years and clinical exams with imaging every 3 months. The conventional arm (A) received carcinoembryonic antigen, liver echography, and alternated between lung radiography and computed tomography (CT) scans. The experimental arm (B) received PET/CT.

RESULTS

A total of 365 patients with colon (79.4%) or rectal cancer (20.6%), stages II (48.2%) or III (50.8%), were enroled in this study. At 36 months, intention-to-treat analysis revealed recurrence in 31 (17.2%) patients in arm A and 47 (25.4%) in arm B (p = 0.063). At 3 years, 7 of 31 relapses (22.5%) in arm A were surgically treated with curative intent, compared to 17 of 47 (36.2%) in arm B (p = 0.25). The rates of recurrence and new cancers were higher in arm B than arm A (p = 0.038).

CONCLUSIONS

PET/CT follow-up every 6 months did not increase the rate of recurrence at 3 years or the rate of surgically treated recurrence compared with conventional follow-up.

Accuracy of 18F-FDG PET/CT in monitoring therapeutic response and detection of loco-regional recurrence and metastatic deposits of colorectal cancer in comparison to CT

Background

The study shows the role of PET/CT in monitoring response to therapy in colorectal cancer as well as detection of loco-regional recurrence and metastatic deposits hence guiding the clinician to the proper management strategy. Sixty patients (41male and 19 female) were included in our study. All patients are pathologically proven colorectal cancer. They had undergone 18F-FDG PET/CT for follow up post-therapeutic (operative, and/or chemotherapy and/or radiotherapy) follow up for metastatic or recurrent colorectal cancer during the period from September 2015 to August 2017.

Results

Our study demonstrated that FDG PET/CT is highly sensitive and specific in assessing local recurrence and distant metastasis in patient with pathologically proved colorectal cancer, with sensitivity 95.45%, specificity 97.3%, and accuracy 96.7% in detection of local recurrence; and sensitivity, specificity, and accuracy of 100% in detection of hepatic metastasis as well as in detection of nodal metastasis.

Conclusion

FDG PET/CT is an accurate modality in the treatment plan of cancer colon in monitoring therapeutic response as well as defining their local extent and distant metastatic disease thus provides valuable information that is very helpful in the clinical decision-making process.

Pitfalls and value of organ specific approach in evaluating indeterminate lesions detected on CT in colorectal cancer by [F18] FDG PET/CT

Objective

The objective of this study is to evaluate the value of FDG PET/CT for different involved organs showing Indeterminate/ equivocal / suspicious lesions detected on IV contrasted CT during surveillance follow up for colorectal cancer.

Materials and methods

A total of 67 patients with colorectal cancer how are on regular surveillance follow up by IV contrasted CT scans revealing indeterminate lesions were studied. Subsequent FDG PET/CT evaluation was performed as a problem solving modality. PET/CT results were statistically characterized when compared to biopsy results or to follow/up results. Also Statistical parameters were calculated for each organ involved. The evaluation of all CT indeterminate lesions by FDG PET/CT showed overall sensitivity of 93%, Specificity of 81%, Negative predictive value of 94%, Positive predictive value 80% and accuracy of 87%. However in an organ specific approach the highest accuracy was for lymph nodes with results showing a 100% accuracy and the lowest accuracy was for local disease at a value of 80%. Probable explanations for the falsely characterized lesions resulting in the pitfalls seen and in the imperfect accuracy were provided.

Conclusion

Study shows that FDG PET/CT is an excellent tool in characterizing CT indeterminate lesions during surveillance of colorectal cancer, However different organs showed variable accuracy results with the highest accuracy for our study was for lymph node status (100%) and the lowest accuracy being for local disease at the original site of primary tumor (80%).

FDG-PET/CT in the Postoperative Period: Utility, Expected Findings, Complications, and Pitfalls

FDG-PET/CT as a modality is increasingly used for detection of recurrence and for restaging in patients with clinical suspicion of malignancy, as well as in patients with elevated tumor markers. However, there are many pitfalls in the interpretation of these scans when the studies are performed after some treatment. Some of these are attributed to normal physiological distribution and are compounded when there are inflammatory changes occurring after surgery. The body's inherent response to the surgical insult results in this inflammation. In addition, there are also complications that can happen following surgery, causing increased FDG uptake. Despite various fallacies, FDG-PET/CT provides valuable information in evaluation of residual and recurrent malignant disease. In this article, we aim to describe some of these postsurgical changes secondary to inflammation, common surgical complications, and finally, the utility of FDG-PET/CT in these patients to detect recurrent disease, even in the background of postsurgical changes.

Characteristics of 18F-fluorodeoxyglucose uptake in anastomotic sinus and fistula following rectal cancer surgery

PURPOSE

To assess the characteristics of 18F-fluorodeoxyglucose (FDG) uptake in persisting anastomotic sinus and fistula following rectal cancer surgery.

METHODS

Eight patients with anastomotic sinus and fistula were retrospectively studied.

RESULTS

A total of 13 anastomotic sinuses (n=11) and fistulas (n=2) were observed. Sixteen FDG-positron emission tomography/computed tomography studies for 13 lesions performed and 26 uptake patterns were evaluated. Twenty-one lesions were found to have diffuse increased uptake, whereas four lesions had focal uptake. There was only one lesion without FDG uptake.

CONCLUSIONS

Increased FDG uptake is frequently observed in anastomotic sinus and fistula, which should be known to avoid making wrong diagnosis.

FDG PET/CT in the management of colorectal and anal cancers

OBJECTIVE

CT remains the imaging modality of choice in the diagnosis of colorectal cancer (CRC) and anal cancer. However, advances in imaging have expanded the role of MRI and PET/CT. This article focuses on the evolving role of FDG PET/CT in the diagnosis, radiation therapy planning, therapy assessment, and posttherapy monitoring of CRC and anal cancer.

CONCLUSION

FDG PET/CT is a valuable imaging modality that impacts the clinical management of patients with CRC and those with anal cancer.

Value of 18F-FDG PET-CT in surveillance of postoperative colorectal cancer patients with various carcinoembryonic antigen concentrations

AIM: To evaluate the value of positron emission tomography (PET)/computerized tomography (CT) in surveillance of colorectal cancer (CRC) patients with different carcinoembryonic antigen (CEA) concentrations.

METHODS: One hundred and six postoperative CRC patients who had suspected recurrence or metastasis and received fluorodeoxyglucose (FDG) PET/CT within one week were included in this study. The final diagnosis was confirmed by histological examination or clinical follow-up over at least six months.

RESULTS: The sensitivity, specificity, and accuracy of FDG PET/CT were 95.2%, 82.6%, and 92.5%, and 94.8%, 81.4% and 92.8%, respectively, in the case- and lesion-based analyses. The sensitivity and accuracy of FDG PET/CT significantly differed from CT in both analyses (χ² = 8.186, P = 0.004; χ² =6.201, P = 0.013; χ² =13.445, P = 0.000; χ² =11.194, P = 0.001). In the lesion-based analysis, the sensitivity, specificity, and accuracy of FDG PET/CT in the abnormal CEA group were 97.8%, 82.6%, and 95.6%, compared with 81.3%, 80%, and 80.6% for patients with normal CEA levels. In case-based analysis, the sensitivity, specificity, and accuracy of FDG PET/CT were 97.2%, 77.8%, and 95% in abnormal CEA group. Only in lesion-based analysis, the sensitivity and accuracy of FDG PET/CT in the abnormal CEA group were significantly superior to those in the normal CEA group (χ² =6.432, P = 0.011; χ² =7.837, P = 0.005). FDG PET/CT changed the management in 45.8% of patients with positive scans.

CONCLUSION: FDG PET/CT showed superior diagnostic value and is an advisable option in surveillance of postoperative CRC patients with a vague diagnosis.

Physician follow-up and observation of guidelines in the post treatment surveillance of colorectal cancer

BACKGROUND

Guidelines for post resection surveillance of colorectal cancer recommend a collection of the patient's history and physical examination, testing for carcinoembryonic antigen (CEA), and colonoscopy. No consistent guidelines exist for the use of abdominal computed tomography (CT) and position emission tomography (PET)/PET-CT. The goal of our study was to describe current trends, the impact of oncologic follow-up on guideline adherence, and the patterns of use of nonrecommended tests.

METHODS

We used Texas Cancer Registry-Medicare-linked data (2000-2009) to identify physician visits, CEA testing, colonoscopy, abdominal CT, and PET/PET-CT scans in patients ≥ 66 years old with stage I-III colorectal cancer who underwent curative resection. Compliance with guidelines was assessed with a composite measure of physician visits, CEA tests, and colonoscopy use from start of surveillance.

RESULTS

In patients who survived 3 years, the overall compliance with guidelines was 25.1%. In patients seen regularly by a medical oncologist, compliance with guidelines increased to 61.5% compared with 8.8% for those not seen by a medical oncologist regularly (P < .0001). The use of abdominal CT and PET/PET-CT increased from 57.5% and 9.5%, respectively, in 2001 to 65.8% and 24.6% (P < .0001) in 2006. Patients who saw a medical oncologist were more likely to get cross-sectional imaging than those who did not (P < .0001).

CONCLUSION

Compliance with current minimum guidelines for post treatment surveillance of colorectal cancer is low and the use of nonrecommended testing has increased over time. Both compliance and use of nonrecommended tests are markedly increased in patients seen by a medical oncologist. The comparative effectiveness of CT and PET/PET-CT in the surveillance of colorectal cancer patients needs further examination.

Clinical Usefulness of Serum CYFRA 21-1 in Patients with Colorectal Cancer

PURPOSE

Among diverse tumor markers, pretreatment evaluation and follow-up detection of recurrence in colorectal cancer are generally evaluated by serum carcinoembryonic antigen (CEA) levels. However, there have been some reports about the low accuracy and high false-positive results of CEA in colorectal cancer. We investigated the clinical utilities of CYFRA 21-1 by comparing CEA and cancer antigen 19-9 (CA 19-9) in pretreatment and recurrent colorectal cancer.

METHODS

Using a solid-phase immunoradiometric assay, serum levels of CYFRA 21-1, CEA and CA 19-9 were analyzed in 132 patients with primary colorectal cancer, 124 healthy controls, 104 patients with benign colorectal disease and 19 patients with recurrent colorectal cancer. We determined three different cutoff values to evaluate the sensitivity of diagnostic performance in pretreatment and recurrent colorectal cancer.

RESULTS

CYFRA 21-1 (≥ 1.13 ng/ml) had a sensitivity of 47 %, compared with 37 % for CEA (≥ 3.05 ng/ml) and 32.6 % for CA 19-9 (≥ 23.1 ng/ml) in the initial staging of primary colorectal cancer. Using different cutoff values, CYFRA 21-1 showed higher sensitivity for pretreatment colorectal cancer than CEA and CA 19-9 in adenocarcinoma and adenosquamous carcinoma of this study. A mildly significant correlative relationship was noted between Dukes' stages and three tumor markers (p < 0.01). The areas under the receiver operating characteristic curves of CYFRA 21-1, CEA and CA 19-9 were 0.81 ± 0.03, 0.74 ± 0.03 and 0.62 ± 0.04, respectively, for discriminating colorectal cancer patients from patients with benign colorectal disease. In addition, CYFRA 21-1 was determined as the most sensitive tumor marker for evaluating recurrent colorectal cancer for all cutoff values.

CONCLUSION

This study showed that CYFRA 21-1 could be a useful and dependable tumor marker for pretreatment and recurrent colorectal cancer. Further prospective studies on its usefulness with respect to the prognosis and utility of combined tumor markers are needed.

Use of FDG-PET or PET/CT to detect recurrent colorectal cancer in patients with elevated CEA: a systematic review and meta-analysis

AIM

The purpose of the present study was to conduct a systematic review and meta-analysis of the published literature to assess the diagnostic performance of FDG-PET or PET/CT in the detection of recurrent colorectal cancer (CRC) rising in patients with elevated CEA.

MATERIALS AND METHODS

The authors conducted a systematic MEDLINE search of published articles. Two reviewers independently assessed the methodological quality of each study. We estimated pooled sensitivity and specificity and positive and negative likelihood ratios, and summary receiver-operating characteristic curves in the detection of recurrent CRC in patients with elevated CEA.

RESULTS

Eleven studies with a total of 510 patients met the inclusion criteria. One hundred and six patients (106/510 = 20.8%) had true-negative FDG-PET (PET/CT) results in detection of recurrent CRC when rising CEA. The pooled estimates of sensitivity and specificity and positive and negative likelihood ratios of FDG-PET in the detection of tumor recurrence in CRC patients with elevated CEA were 90.3% (95% CI, 85.5-94.0%), 80.0% (95% CI, 67.0-89.6%), 2.88 (95% CI, 1.37-6.07), and 0.12 (95% CI, 0.07-0.20), respectively. The pooled estimates of sensitivity and specificity and positive and negative likelihood ratios of FDG-PET/CT in the detection of tumor recurrence in CRC patients with elevated CEA were 94.1% (95% CI, 89.4-97.1%), 77.2% (95% CI, 66.4-85.9%), 4.70 (95% CI, 0.82-12.13), and 0.06 (95% CI, 0.03-0.13), respectively.

CONCLUSIONS

Whole-body FDG-PET and PET/CT are valuable imaging tools for the assessment of patients with suspected CRC tumor recurrence based on the increase of CEA.

Detection of resectable recurrences in colorectal cancer patients with 2-[18F]fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography

PURPOSE

To evaluate the usefulness of 2-[(18)F]fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) in the early detection of resectable recurrences of colorectal cancer (CRC) and the impacts on the clinical disease management.

METHODS

FDG-PET/CT was performed on patients with elevated serum carcinoembryonic antigen (CEA) levels >5 ng/mL (Group 1) or suspicious recurrences without rise in serum CEA levels (Group 2). The results were analyzed on the basis of histological data, disease progression, and/or clinical follow-up. Recurrence was defined as evidence of recurrent lesions within 6 months of the FDG-PET/CT scan. Resectable recurrences and changes in management were calculated based on medical records.

RESULTS

In our study, 128 consecutive FDG-PET/CT analyses (n=49 in Group 1 and n=79 in Group 2) were performed on 96 recruited patients. Recurrences were proven in 63. The overall sensitivity, specificity, and accuracy of FDG-PET/CT were 98.4%, 89.2%, and 93.8%, respectively, and were 100%, 88.9%, and 95.9% in Group 1 and 96.9% and 89.4% and 92.4% in Group 2, respectively. Surgical resections were performed in 38.7% (12/31) of Group 1 patients and 53.1% (17/32) of Group 2 patients. FDG-PET/CT induced changes in planned management in 48.4% (62/128) of all patients, which included 63.3% (31/49) of Group 1 patients and 39.2% (31/79) of Group 2 patients (p=0.008). After a follow-up, 3.4% (1/29) of patients who underwent surgical resection of recurrent lesions and 34.3% (11/34) patients who did not undergo resection died at the end of study (p=0.004).

CONCLUSIONS

The surgical resection of limited recurrent disease, as determined by FDG-PET/CT, improves the survival of CRC patients. FDG-PET/CT should be performed not only in patients with elevated serum CEA levels, but also in those in whom recurrences are suspected to improve the early detection of resectable disease.

Serum carcinoembryonic antigen measurement, abdominal contrast-enhanced computed tomography, and fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography in the detection of colorectal cancer recurrence: a correlative study

INTRODUCTION

The aim of this study was to evaluate the correlative role of fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) in carcinoembryonic antigen (CEA) measurement and contrast-enhanced abdominal computed tomography (ceCT) in the detection of colorectal cancer (CRC) recurrence.

MATERIALS AND METHODS

A total of 96 patients (40 female, 56 male; mean age, 60.6 ± 12 years) with a previous diagnosis of CRC underwent 18F-FDG PET/CT on suspicion of recurrence and were evaluated retrospectively. Inclusion criteria were accepted as the presence of increased serum CEA levels or positive findings on abdominal ceCT or both. 18F-FDG PET/CT findings were compared with histopathological findings and/or clinical follow-up data as the gold standard. Patients were divided into three groups: group 1, with increased CEA levels and normal abdominal ceCT; group 2, with normal CEA levels and positive ceCT; and group 3, with increased CEA levels and positive ceCT.

RESULTS

Whereas sensitivities of CEA, ceCT, and 18F-FDG PET/CT in the three patient groups were calculated as 91, 67, and 96%, specificities were 13, 51, and 62%, respectively. There were 35, 14, and 46 patients in groups 1, 2, and 3, respectively. In separate analyses conducted on the groups, sensitivity of 18F-FDG PET/CT was computed as 100 and 100% and specificity as 88 and 80% for groups 1 and 2. In group 3, which comprised four patients with secondary malignancies, sensitivity and specificity of 18F-FDG PET/CT were 94 and 16%, respectively.

CONCLUSION

18F-FDG PET/CT has an additional role in the detection of CRC recurrence with a higher sensitivity compared with CEA and ceCT alone, and 18F-FDG PET/CT is especially more successful in patients with isolated elevated CEA levels or positive ceCT findings without accompanying CEA elevation.

Value of Surveillance (18)F-FDG PET/CT in Colorectal Cancer: Comparison with Conventional Imaging Studies

PURPOSE

To assess the value of PET/CT for detecting local or distant recurrence in patients who undergo surgery for colorectal cancer (CRC) and to compare the accuracy of PET/CT to that of conventional imaging studies (CIS).

METHODS

Tumor surveillance PET/CT scans done between March 2005 and December 2009 of disease-free patients after surgery with or without adjuvant chemotherapy for CRC were retrospectively studied. CIS (serial enhanced CT from lung base to pelvis and plain chest radiograph) were performed within 1 month of PET/CT. We excluded patients with distant metastasis on initial staging, a known recurrent tumor, and a lack of follow-up imaging. The final diagnosis was based on at least 6 months of follow-up with colonoscopy, biopsy, and serial imaging studies in combination with carcinoembryonic antigen levels.

RESULTS

A total of 262 PET/CT scans of 245 patients were included. Local and distant recurrences were detected in 27 cases (10.3%). On case-based analysis, the overall sensitivity, specificity, and accuracy were 100, 97.0, and 97.3% for PET/CT and 85.1, 97.0, and 95.8% for CIS, respectively. On lesion-based analysis, PET/CT detected more lesions compared to CIS in local recurrence and lung metastasis. PET/CT and CIS detected the same number of lesions in abdominal lymph nodes, hepatic metastasis, and peritoneal carcinomatosis. PET/CT detected two more metachronous tumors than did CIS in the lung and thyroid gland.

CONCLUSION

PET/CT detected more recurrences in patients who underwent surgery for CRC than did CIS and had the additional advantage of evaluating the entire body during a single scan.

The role of 18F-FDG PET/CT in detecting colorectal cancer recurrence in patients with elevated CEA levels

INTRODUCTION

In this study we aimed to define the success of fluorine-18 (18F) fluorodeoxyglucose (FDG) PET/computed tomography (PET/CT) in detecting recurrent disease in our patient group with colorectal cancer (CRC) and elevated carcinoembryonic antigen (CEA) levels.

MATERIAL AND METHOD

Patients who had a previous diagnosis of CRC were searched retrospectively in our PET center database. Seventy-six 18F-FDG PET/CT studies between October 2006 and December 2010 of 69 patients (25 women, 44 men; mean age: 61.61 ± 4.1 years) with elevated CEA levels were evaluated. 18F-FDG PET/CT findings and concurrent abdominopelvic contrast-enhanced computed tomography (ceCT) findings were compared with histopathological findings and/or clinical follow-up data as the 'gold standard'.

RESULTS

In the patient-based analysis, the sensitivity and specificity of 18F-FDG PET/CT in the detection of disease recurrence were calculated as 97 and 61%, respectively. A statistically significant difference was found in frequencies of positive and negative 18F-FDG PET/CT findings between patients with or without recurrent disease by gold standard (P<0.05). There was no correlation between patients' serum CEA levels and lesions' maximum standardized uptake values (P=0.85). The sensitivity and specificity of ceCT were computed as 51 and 60%, respectively. In the evaluation of separate patient groups, although the sensitivity and specificity of 18F-FDG PET/CT were calculated as 100 and 60% in the group whose CEA level elevation was less than two-fold (5-9.9 ng/ml), these were 100 and 75% in the group with CEA elevation less than three-fold (10-14.9 ng/ml) and 95 and 62% in the group with elevation more than three-fold (≥ 15 ng/ml). The sensitivity and specificity of 18F-FDG PET/CT were computed as 98 and 85% in the lesion-based evaluation. The sensitivity and specificity of ceCT were 73 and 86%, respectively.

CONCLUSION

18F-FDG PET/CT is a safe imaging method that can be used in the determination of CRC recurrence in patients with elevated CEA levels, regardless of the CEA level.

[Dual-time point images of the liver with (18)F-FDG PET/CT in suspected recurrence from colorectal cancer]

AIM

To analyze the potential improvement of (18)F-fluorodeoxyglucose (FDG) PET/CT using additional delayed images of the liver in operated colorectal cancer.

MATERIAL AND METHODS

The study prospectively included 71 patients (22 women, 49 men) with mean age of 65 ± 11 years with clinical, analytic or radiological suspicion of current disease. A whole body PET/CT scan was performed at 60 min. (standard images) and after 2 hr (delayed images) post-injection of 4.07 MBq/Kg of (18)F-FDG. Visual and quantitative SUV analysis of PET/CT findings was done. All findings were confirmed by histopathology and/or at least 6 months follow-up.

RESULTS

Thirty-seven out of 71 patients were diagnosed of liver metastases (79 metastases). In 38/71 cases there was extra-hepatic disease in the form of local recurrence (10), abdominopelvic (3) or mediastinal (3) lymph nodes, bone (1) or lung metastases (16) and carcinomatosis (10). Sensitivity and specificity in the diagnosis of liver metastases in a patient-by-patient basis in standard (81% and 91%) and in delayed images (95% y 97%) was calculated. The number of lesions detected in delayed images was significantly higher (66/79) than in standard images (57/79). Sensitivity and specificity for PET/CT in the diagnosis of extra-hepatic disease was 84% and 70%, contributing to the detection of synchronous tumors in 5 patients.

CONCLUSIONS

PET/CT may be useful in the diagnosis of extra-hepatic disease in suspected recurrence of colorectal cancer. Delayed images on PET/CT may increase the sensitivity to identify liver metastases.