The Use of PET-CT in the Assessment of Patients with Colorectal Carcinoma

Tailoring the clinical management of colorectal cancer by 18F-FDG PET/CT

Colorectal cancer (CRC) is among the most commonly diagnosed gastrointestinal malignancies worldwide. It is inadequate to handle in terms of staging and restaging only based on morphological imaging modalities and serum surrogate markers. And the correct and timely staging of CRC is imperative to prognosis and management. When compared to established sequential, multimodal conventional diagnostic methods, the molecular and functional imaging ¹⁸F-FDG PET/CT shows superiorities for tailoring appropriate treatment maneuvers to each patient. This review aims to summarize the utilities of ¹⁸F-FDG PET/CT in CRC, focusing on primary staging, follow-up assessment of tumor responses and diagnostic of recurrence. In addition, we also summarize the technical considerations of PET/CT and the conventional imaging modalities in those patients who are either newly diagnosed with CRC or has already been treated from this cancer.

Prediction value of 18F-FDG PET/CT intratumor metabolic heterogeneity parameters for recurrence after radical surgery of stage II/III colorectal cancer

Purpose

We explored the predictive effect of intratumor metabolic heterogeneity indices extracted from ¹⁸F-FDG PET/CT on recurrence in stage II/III colorectal cancer after radical surgery.

Methods

A total of 140 stage II/III colorectal cancer patients who received preoperative ¹⁸F-FDG PET/CT and radical resection were enrolled. ¹⁸F-FDG traditional parameters including the maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) under different thresholds; heterogeneity indices including the coefficient of variation with SUV 2.5 as a threshold (CV2.5), CV40%, heterogeneity index-1 (HI-1) calculated by the fixed-threshold method, and HI-2 calculated by the percentage threshold method; and clinicopathological information were collected. We concluded that relationships exist between these data and patients’ disease-free survival (DFS).

Results

Regional lymph node status (P < 0.001), nerve invasion (P = 0.036), tumor thrombus (P = 0.005), and HI-1 (P = 0.010) exhibited significant differences between the relapse and non-relapse groups, while SUVmax, MTV2.5, MTV40%, TLG2.5, TLG40%, CV2.5, CV40%, HI-2, and other clinicopathological factors had no differences between the relapse and non-relapse groups. Multivariate analysis demonstrated that HI-1 (HR = 1.02, 1.00–1.04, P = 0.038), regional lymph node metastasis (HR = 2.95, 1.37–6.38, P = 0.006), and tumor thrombus status (HR = 2.37, 1.13–4.99, P = 0.022) were independent factors significantly related to DFS.

Conclusion

HI-1, tumor thrombus status, and regional lymph node status could predict the recurrence of stage II/III colorectal cancer after radical resection and had an advantage over other ¹⁸F-FDG PET/CT conventional parameters and heterogeneity indices.

Kolorektal kanseri olan hastaların ameliyat sonrası klinik yönetiminde fluorine-18 fluorodeoxyglucose pozitron emisyon tomografisi/bilgisayarlı tomografi’nin tanısal önemi

Amaç: Kolorektal kanser, erken tespitinde cerrahi kür sağlanabilen yaygın bir kanser türüdür. Bu kanser tipinde tedaviye yanıtın erken belirlenmesi yaşam süresini olumlu etkilemektedir. Çalışmamızda kolorektal kanseri olan hastaların, ameliyat sonrasındaki klinik yönetimlerinde F-18 FDG PET/BT’nin tanısal önemini değerlendirmeyi amaçladık. Gereç ve Yöntem: Haziran 2016 ve Ocak 2020 tarihleri arasında 168 hasta kolorektal kanser yönetimi amacıyla bölümümüze yönlendirilmiştir. Bu hastaların hepsi primer kolon tümörleri için ameliyat edilmişlerdi. Sistemik tedavi öncesinde ve sonrasında tedavi yanıtının değerlendirilmesi amacıyla bazal ve ardışık F-18 FDG PET/BT incelemesi yapılmıştır. F-18 FDG PET/BT taramaları sırasıyla analiz edilmiştir. Bulgular: Hastalar primer tümör lokalizasyonlarına göre gruplandırıldı. Toplam 168 hastanın 55’inde sağ kolonda, 33’ünde sol kolonda, 14’ünde transvers kolonda, 61’inde rektosigmoid kolonda ve 5’inde çekumda primer tümör saptandı. Lokal rekürrens 57 hastada saptanmış olup 33’ü erkek (%57.9) ve 24’ü (%42.1) kadındı. Lokal rekürrense ait ortalama SUVmaks 8.97±3.42 g/ml olarak saptandı. Ek olarak çıkan kolon grubunda 2 hastada (%1.20) yeni tümöral odak gözlendi. Sonuç: Kolorektal kanserli hastalarda, yapılabiliyorsa kolon rezeksiyonu tedavide ilk aşamadır. Küratif cerrahi sonrası ilk iki yıl içinde, hastaların yaklaşık %40’ında rekürrens görülebilmektedir. Rekürrensin erken tespiti, hastaların yaşam süresini iyileştirmektedir.

FDG PET/CT in follow UP patients with colorectal carcinoma after adjuvant chemotherapy

Background

18F-2-fluoro-2-deoxy-d-glucose (18F-FDG) positron emission tomography-computed tomography (PET-CT) is a method of imaging that assesses and measures metabolic avidity in cancer cells, acting as a proxy for underlying cellular activity and vitality and so providing anatomic and metabolic information. 18F-FDG PET-CT is beneficial for detecting local recurrence, distant metastases, and monitoring tumor viability after chemotherapy and radiotherapy in patients with colorectal cancer. Strict adherence to set protocols, technological processes, and good patient preparation are essential to produce the greatest results. The goal of the trial was to see how useful PET/CT was in following up on patients who had resected colorectal cancer and had completed adjuvant chemotherapy rounds.

Results

In this study, PET/CT early detected hepatic deposits, pulmonary masses, bone deposits, and sizable LNs. PET/CT provided useful information and had a considerable impact on disease management, enabling the detection of recurrent disease as early as possible with high accuracy in assessment of therapeutic response. It detected viable residual tumor cells in operative bed scar, small metabolically active LNs, hepatic focal lesions, peritoneal deposits, pulmonary secondaries, and bone deposits avoiding unnecessary surgeries.

Conclusion

Because of its high accuracy in detection and capacity to identify recurrent illness, FDG-PET-CT imaging is effective in evaluating post-therapeutic colorectal cancer patients with suspected tumor recurrence or distant metastases.

Follow-up of colorectal cancer and patterns of recurrence

Colorectal cancer is one of the commonest cancers detected as also amongst the most common causes of cancer death. Survival has improved due to better disease understanding and treatment; however, a substantial proportion of patients recur after curative intent therapy. In this article, we will discuss the imaging features of recurrent colorectal cancer and the role of the radiologist in its management.

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.

Role of 18F-FDG PET/CT in the Follow-up of Colorectal Cancer

INTRODUCTION

Colorectal cancer (CRC) is the third most common cancer worldwide with the incidence of about 1,8 million newly diagnosed cases in 2018. According to the World Cancer Report 2014, in Bosnia and Herzegovina 6700 people died of cancer in 2014, and CRC was the cause of mortality in 724 patients (10%). Prevention programs including screening, state-of-the-art diagnostic modalities and therapeutic approaches to CRC are being constantly improved.

AIM

Our study was designed to address the diagnostic accuracy of 18F-FDG PET/CT in the follow-up of CRC in patients with normal or elevated CEA.

METHODS

We retrospectively analyzed 50 patients previously diagnosed with CRC who were initially surgically treated. All patients were suspicious of recurrence and were referred to as 18F-FDG PET/CT for restaging between February 2014 and February 2019. Possible recurrence was indicated by rising CEA, equivocal radiological findings or clinical findings.

RESULTS

Out of a total of 50 patients for whom the follow-up of at least six months was available, 27 had CRC confirmed with the gold standard, and all 27 patients had 18F-FDG PET/CT positive for recurrence, giving a sensitivity of 18F-FDG PET/CT in detecting the recurrence of CRC of 100.0% (0.0% of false-negative - FN results). Out of 23 patients with no signs of CRC recurrence on the gold standard, 19 were also 18F-FDG PET/CT negative, giving a specificity of 18F-FDG PET/CT in detecting the recurrence of CRC of 82.6%, and 17.4% of false-positive - FP results. Out of 31 patients who were 18F-FDG PET/CT positive, 27 had it confirmed pathophysiologically or clinically, giving positive predictive value (PPV) of 18F-FDG PET/CT in detecting CRC recurrence of 87.1%; negative predictive value (NPV) was 100.0%, meaning all 19 patients showing no signs of CRC recurrence when imaged with 18F-FDG PET/CT were gold standard negative as well.

CONCLUSION

18F-FDG PET/CT proves to be a valid diagnostic tool in detecting recurrence in patients with CRC.

Reliability of Contrast CT and Positron Emission Tomography in Post-Surgical Colorectal Cancer and Its Association with Obesity

BACKGROUND

Post-surgical recurrence of cancer colon occurs in one-third of patients within the first two years, so early detection is important. The assessment of the therapeutic response is important to change protocol strategy. Positron emission tomography/computed tomography PET/CT, a valuable tool gives both metabolic and anatomic information for whole-body regions. Obesity is an important risk factor for colorectal cancer.

AIM

To evaluate post-surgical and therapeutic colorectal cancer by PET/CT and study obesity association to its prognosis.

METHODS

This was a prospective study involved 93 patients with, post-surgical colorectal cancer examined by PET/CT, then follow up after 4-6 months.

RESULTS

There was a statistically significant difference between PET/CT and contrast CT. The sensitivity& the specificity were (96.4%-100% & 92.3%-98.2%) for PET/CT and (84.2%-90.2% & 76.5%-85.4%) for contrast CT respectively. Post-therapeutic follow up showed; progressive course (24.5%), stationary course (26.4%), partial regression (28.3%) and complete regression course (20.8%). Obesity is a risk factor for progression with highly statistically significant to treatment response. Obese patients had a progressive or stationary course of the disease. Also, there was a highly statistically significant association between total abdominal fat & visceral abdominal fat areas with good response of treatment.

CONCLUSION

PET/CT is the most appropriate imaging technique to detect any recurrence or metastases in post-surgical colorectal cancer with high sensitivity and specificity comparing to CT. Obesity is a predictor risk factor for prognosis of the disease, as generally and abdominally (total & visceral fat) had an association with therapeutic response.

The value of using fludeoxyglucose positron-emission tomography scan with respect to colorectal abnormalities-a cross-sectional study

Background

Fludeoxyglucose positron-emission tomography (FDG-PET) shows colic uptake regularly. Complementary colonoscopy is done. Aim: study the findings of colonoscopy.

Methods

All consecutive scans in 5 years were studied. Focal FDG uptake in colon and/or rectum were scored as + or ++. Clinical files and endoscopy reports were studied for final diagnosis.

Results

Focal FDG uptake was noted in 173 out of 2,075 scans (8.4%). Focal FDG activity was judged ++ in 73 patients (42.2%) and + in 100 (57.8%). The majority of colorectal cancers scored ++. Patients with ++ activity underwent or had undergone significantly more often a colonoscopy compared with patients with + activity, 82% versus 65% (P=0.02). FDG PET/CT was false positive with respect to polyp(s) or cancer in 13 cases (22%) of ++ FGD activity and in 38 cases of + FDG (P<0.001). In 25 patients a total of 69 polyps were not FDG avid.

Conclusions

FDG-PET scanning is a useful tool in oncology. However, false-positive and false-negative findings with respect to colonic uptake are present in a significant number of patients. If the clinical condition and the potential prognosis allows the performance of colonoscopy this procedure should be done.

Early PET-CT in patients with pathological stage III colon cancer may improve their outcome: Results from a large retrospective study

Background

Current staging of pathological stage III colon cancer (CC) is suboptimal; many patients recur despite unremarkable preoperative staging. We previously reported that early postoperative PET‐CT can alter the stage and management of up to 15% of patients with high‐risk stage III CC. This study aimed to determine the role of the test in the general stage III CC population.

Methods

A retrospective study of all consecutive patients with stage III CC who underwent early postoperative PET‐CT between 2005 and 2017.

Results

A total of 342 patients, 166 (48.5%) males, median age 66 years (range, 29‐90), were included. Pathological stage was IIIA, IIIB, and IIIC in 18 (5.3%), 257 (75.1%), and 67 (19.6%) patients, respectively. Median number of positive lymph nodes was 2 (range, 0‐32). PET‐CT results modified the management of 46 patients (13.4%): 37 (10.8%) with overt metastatic disease and 9 (2.6%) with a second primary. The 5‐year disease‐free survival for true stage III patients was 81%. The median overall survival for the entire cohort and for true stage III patients was not reached and was 57.2 months for true stage IV. Of the 37 patients found to be metastatic, 14 (37.8%) underwent curative treatments and 9/14 (64.3%) remain disease‐free, with a median follow‐up of 83.8 months. Predictive factors for upstaging following PET‐CT were identified.

Conclusion

Early postoperative PET‐CT changed the staging and treatment of 13.4% of stage III CC patients and has the potential for early detection of curable metastatic disease. Outcome results are encouraging. Prospective validation is ongoing.

Implication of atypical supraclavicular F18-fluorodeoxyglucose uptake in patients with breast cancer: Association between brown adipose tissue and breast cancer

It has been reported that F18-fluorodeoxyglucose (FDG) uptake in the neck and supraclavicular lesions represents activated brown adipose tissue (BAT). In the present study, the association between BAT activity, detected by FDG-positron emission tomography (PET), and the clinicopathological features of patients with breast cancer was investigated. The cases of 156 consecutive patients with breast cancer who underwent FDG-PET preoperatively were analyzed. The distribution and intensity of atypical FDG uptake in the neck and/or supraclavicular region was reviewed. The intensity was graded as follows: 1, weak; 2, moderate; and 3, intense. Among the 156 patients, 70 (44.9%) exhibited grade 1 intensity, 65 (41.7%) exhibited grade 2 intensity and 21 (13.5%) exhibited grade 3 intensity. The intensity of FDG was significantly associated with human epidermal growth factor receptor 2 (HER2) expression and progesterone expression. Among the 156 patients, 6 (3.8%) had recurrent disease. Multivariate analysis revealed that showing a low grade of atypical FDG uptake was the only independent risk factor of short-term recurrence, and none of the patients with recurrent disease had atypical FDG uptake that may reflect the activation of BAT. These results indicated that the presence of BAT is associated with HER2 expression and the absence of BAT may be a prognostic factor for breast cancer.

18F-FDG PET as novel imaging biomarker for disease progression after ablation therapy in colorectal liver metastases

Purpose

Recurrent disease following thermal ablation therapy is a frequently reported problem. Preoperative identification of patients with high risk of recurrent disease might enable individualized treatment based on patients’ risk profile. The aim of the present work was to investigate the role of metabolic parameters derived from the pre-ablation ¹⁸F-FDG PET/CT as imaging biomarkers for recurrent disease in patients with colorectal liver metastases (CLM).

Methods

Included in this retrospective study were all consecutive patients with CLM treated with percutaneous or open thermal ablation therapy who had a pre-treatment baseline ¹⁸F-FDG PET/CT available. Multivariable cox regression for survival analysis was performed using different models for the metabolic parameters (SUL_peak, SUL_mean, SUL_max, partial volume corrected SUL_mean (cSUL_mean), and total lesion glycolysis (TLG)) corrected for tumour and procedure characteristics. The study endpoints were defined as local tumour progression free survival (LTP-FS), new intrahepatic recurrence free survival (NHR-FS) and extrahepatic recurrence free survival (EHR-FS). Clinical and imaging follow-up data was used as the reference standard.

Results

Fifty-four patients with 90 lesions were selected. Univariable cox regression analysis resulted in eight models. Multivariable analysis revealed that after adjusting for lesion size and the approach of the procedure, none of the metabolic parameters were associated with LTP-FS or EHR-FS. Percutaneous approach was significantly associated with a shorter LTP-FS. It was demonstrated that lower values of SUL_peak, SUL_max, SUL_mean , and cSUL_mean are associated with a significant better NHR-FS, independent of the lesion size and number and prior chemotherapy.

Conclusion

We found no association between the metabolic parameters on pre-ablation ¹⁸F-FDG PET/CT and the LTP-FS. However, low values of the metabolic parameters were significantly associated with improved NHR-FS. The clinical implication of these findings might be the identification of high-risk patients who might benefit most from adjuvant or combined treatment strategies.

Electronic supplementary material

The online version of this article (doi:10.1007/s00259-017-3637-0) contains supplementary material, which is available to authorized users.

Granuloma Mimicking Local Recurrence on PET/CT after Liver Resection of Colorectal Liver Metastasis: A Case Report

Positron emission tomography–computed tomography (PET/CT) improves the diagnostic interpretation of fluorine-18 fluorodeoxyglucose (18F-FDG ) PET and CT in oncologic patients and has an impact on both diagnostic and therapeutic aspects of patient management. However, false positive findings from the PET/CT imaging should be taken into consideration as they mislead physicians into improper therapeutic actions. We present a 48-year-old female patient with a history of left colectomy for colorectal cancer and subsequent liver metastasectomy. After one year of follow-up, she presented with a highly suspicious lesion in the liver, which was confirmed on PET/CT as a metastatic liver tumor. Consequently, the patient underwent surgical excision of the tumor, and the definitive histological diagnosis showed a granulomatous tissue with giant cells and foreign body tissue reaction. Based on this report, we briefly review the dangerous pitfalls from radiological and PET/CT imaging concerning the preoperative diagnostic workup examination, as they may significantly alter the treatment plan in oncologic patients.

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.

FDG PET/CT in the liver: lesions mimicking malignancies

PURPOSE

18F-fluorodeoxyglucose (FDG) PET/CT is invaluable in managing liver lesions, in particular in the evaluation of suspected liver metastases. It is both sensitive and specific in detecting liver metastases from a wide range of primary cancers, and may change clinical management, most commonly by detecting additional lesions and decreasing the number of futile surgeries. However, some benign lesions may also show increased metabolic activity which can lead to false positive PET findings. We describe some of these lesions and their imaging characteristics that may help in differentiating them from malignant metastases.

METHODS

e reviewed all whole body FDG PET/CT studies performed over a 5-year period in our institution, and identified those with focal liver lesions showing increased FDG uptake for which histological results were available.

RESULTS

majority of lesions showing increased metabolic activity were due to malignant disease, such as metastases or primary liver tumours. However, we also found increased FDG uptake in non-neoplastic lesions such as Cryptococcosis, abscesses, and secondary inflammation from cholecystitis. Increased metabolic activity was also seen in some benign neoplasms such as hepatic adenomas and hemangioendotheliomas.

CONCLUSION

DG PET/CT is currently the most sensitive non-invasive imaging modality for the detection of hepatic metastases, particularly from the gastrointestinal tract. False positive results are rare, and have been described mainly in abscesses. However, other lesions can also show increased metabolic activity, and failure to differentiate these from metastases may result in inappropriate treatment.

An FDG-PET/CT-positive lesion mimicking local recurrence of colon cancer 5 years after radical colectomy

Patient: Female, 75

Final Diagnosis: False positive findings

Symptoms: —

Medication: —

Clinical Procedure: —

Specialty: Surgery

Update on the role of imaging in management of metastatic colorectal cancer

Evolution in the treatment of metastatic colorectal cancer (mCRC) has led to significant improvement in the survival of these patients. Surgery is useful in patients with resectable disease. Liver-directed therapies such as hepatic arterial infusion, transarterial radio- and chemoembolization, and percutaneous ablation are sometimes used by oncologists when the liver is the only site of metastatic disease. Unresectable mCRC is typically treated with systemic chemotherapy. First-line systemic chemotherapeutic regimens for mCRC are FOLFOX (combination of 5-fluorouracil/leucovorin [5-FU/LV] and oxaliplatin) and FOLFIRI (combination of 5-FU/LV and irinotecan) combined with molecular targeted drugs. Molecular targeted therapies that are effective in treating mCRC include antiangiogenic agents such as bevacizumab-an antibody against vascular endothelial growth factor-and antibodies directed against epidermal growth factor receptor (EGFR). EGFR-directed antibodies such as cetuximab and panitumumab have been shown to produce activity only in wild-type KRAS tumors. Imaging modalities such as multidetector computed tomography (CT), magnetic resonance imaging, and positron emission tomography/CT play a major role in the selection of appropriate treatment strategies. Assessment of treatment response in patients who undergo liver-directed and systemic therapy requires imaging at regular intervals. Recent studies have shown that alternative treatment response criteria may be more predictive of pathologic response in mCRC than conventional criteria such as Response Evaluation Criteria in Solid Tumors. Awareness of unusual response patterns, as well as of complications and toxicities, is helpful in guiding patient management.

FDG-PET/CT of schwannomas arising in the brachial plexus mimicking lymph node metastasis: report of two cases

Background

Schwannoma is a tumor that develops on peripheral nerves or spinal roots. Although any part of the body can be affected, axillar and supraclavicular lesions are unusual for schwannoma. We report two cases of schwannoma arising in the brachial plexus, which were detected by ¹⁸F-fluorodeoxyglucose positron emission tomography and computed tomography (FDG-PET/CT).

Case 1

A 75-year-old Japanese woman showed high FDG accumulation in a subclavicular or axillary lesion found by FDG-PET/CT. Axillar-subclavicular lymph node metastasis was suspected and surgical excision was performed. Histological evaluation revealed schwannoma.

Case 2

A 75-year-old Japanese woman was diagnosed with suspected primary lung cancer with brain metastases. She showed high FDG uptake at a subclavicular or axillary lesion found by FDG-PET/CT. Surgical excision was performed to arrive at a definitive diagnosis. The mass was located at the trunk of the brachial plexus and was identified as a schwannoma.

Conclusion

Although schwannoma within an axillar or subclavicular lesion is relatively rare, brachial plexus schwannoma should be considered in the diagnosis of masses detected by FDG-PET/CT.

Value of CT, FDG PET-CT and serum tumor markers in staging recurrent colorectal cancer

BACKGROUND

Serum tumor markers and computed tomography (CT) are the most widely accepted monitoring tools for the follow-up patients with colorectal cancer (CRC). Positron emission tomography (PET) with 18[F]-fluorodeoxyglucose (FDG) is a promising modality for the evaluation of recurrent CRC. The purpose of this study was to (1) investigate the sensitivity and specificity of serum tumor marker assay, CT and FDG PET-CT, (2) determine the correlation of these markers with FDG PET-CT quantitative indices such as maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) in patients suspected to have recurrent CRC.

PATIENTS

FDG PET-CT imaging was performed in 212 patients with possible CRC recurrence. A retrospective study was performed on patients with (1) a history of CRC with complete remission after treatment, (2) pathology of adenocarcinoma and (3) increase in cancer antigen 19-9 (CA 19-9) and/or carcinoembryonic antigen (CEA) or suspicious radiological evaluation during follow-up after complete remission.

METHODS

All patients underwent integrated FDG PET-CT scan. Serum tumor markers were obtained within 3 months of PET-CT. All enrolled cases showed increase in a tumor marker over the reference value on at least two serial measurements or abnormal CT scan before PET-CT was performed. Results were compared with histopathological findings or clinical follow-up.

RESULTS

Following exclusion of 57 patients with missing data or lost to follow-up, 155 patients (87 men, mean age: 61 years) remained for final analysis. Serum CEA and CA 19-9 had a sensitivity of 74 and 35% and specificity of 86 and 83% for the detection recurrent CRC, respectively. The sensitivities of CT and FDG PET-CT were 79 and 92% and specificities were 45 and 100%, respectively. At an adaptive threshold of 42%, the median SUVmax, SUVmean, MTV and TLG of these lesions were 8.8, 5.2, 11.3 cm[Formula: see text] and 55.4, respectively. All FDG PET-CT quantitative parameters correlated positively with serum CEA levels, and the correlation coefficients were 0.45, 0.44 and 0.49 for SUVmax, MTV and TLG [Formula: see text].

CONCLUSION

PET-CT scan, CEA and CA-19-9 results were correlated. However, both tumor markers had poor sensitivity to detect metastatic disease. PET-CT is more accurate than CT in detecting recurrent CRC in this study. Majority of the recurrences were in the liver and the sensitivity is affected by tumor histology. The correlation between semiquantitative FDG PET parameters and serum tumor marker levels is moderate.

An EGFR targeted PET imaging probe for the detection of colonic adenocarcinomas in the setting of colitis

Colorectal cancer is a serious complication associated with inflammatory bowel disease, often indistinguishable by screening with conventional FDG PET probes. We have developed an alternative EGFR-targeted PET imaging probe that may be used to overcome this difficulty, and successfully assessed its utility for neoplastic lesion detection in preclinical models. Cetuximab F(ab′)2 fragments were enzymatically generated, purified, and DOTA-conjugated. Radiolabeling was performed with ⁶⁷Ga for cell based studies and ⁶⁴Cu for in vivo imaging. Competitive binding studies were performed on CT26 cells to assess affinity (K_D) and receptors per cell (B_max). In vivo imaging using the EGFR targeted PET probe and ¹⁸F FDG was performed on CT26 tumor bearing mice in both control and dextran sodium sulfate (DSS) induced colitis settings. Spontaneous adenomas in genetically engineered mouse (GEM) models of colon cancer were additionally imaged. The EGFR imaging agent was generated with high purity (> 98%), with a labeling efficiency of 60 ± 5% and ≥99% radiochemical purity. The K_D was 6.6 ± 0.7 nM and the B_max for CT26 cells was 3.3 ± 0.1 × 10⁶ receptors/cell. Target to background ratios (TBR) for CT26 tumors compared to colonic uptake demonstrated high values for both ¹⁸F-FDG (3.95 ± 0.13) and the developed ⁶⁴Cu-DOTA-cetuximab-F(ab′)2 probe (4.42 ± 0.11) in control mice. The TBR for the EGFR targeted probe remained high (3.78 ± 0.06) in the setting of colitis, while for ¹⁸F FDG, this was markedly reduced (1.54 ± 0.08). Assessment of the EGFR targeted probe in the GEM models demonstrated a correlation between radiotracer uptake in spontaneous colonic lesions and the EGFR staining level ex vivo. A clinically translatable PET imaging probe was successfully developed to assess EGFR. The imaging agent can detect colonic tumors with a high TBR for detection of in situ lesions in the setting of colitis, and opens the possibility for a new approach for screening high-risk patients.

Use of (18)F-fluorodeoxyglucose positron emission tomography-computed tomography to aid in diagnosing intestinal adenocarcinoma in 2 rhesus macaques (Macaca mulatta)

Two aged female rhesus macaques (Macaca mulatta) presented with weight loss and intermittent inappetence. The signalment and constellation of clinical signs led clinicians to suspect the presence of intestinal adenocarcinoma. Because of each animal's advanced age and inconclusive radiographic findings, a noninvasive diagnostic tool was preferred over exploratory laparotomy to assist in determining a diagnosis. Consequently, 2-[(18)F]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography-CT (FDG-PET-CT) was chosen to aid in confirming a suspicion of gastrointestinal adenocarcinoma in both animals. FDG is a glucose analogue labeled with fluorine-18 and is taken up by highly metabolically active cells, as observed in many cancers. Tomography revealed an annular constriction of the small intestine with focal FDG uptake in one animal, and an FDG avid transmural mass in the ascending colon of the second animal. Necropsy later confirmed both sites to be adenocarcinomas. This report supports the use of FDG-PET-CT as an adjunct to conventional radiography in the diagnosis of intestinal adenocarcinoma in nonhuman primates.

Positron emission tomography/computed tomography in the staging of colon cancer

Purpose

Accurate preoperative staging of colon cancer is essential for providing the optimal treatment strategy and evaluating the expected prognosis. The aim of this study is to assess the value of positron emission tomography/computed tomography (PET/CT) over conventional studies in the staging of colon cancer.

Methods

A total of 266 colon cancer patients diagnosed between January 2008 and December 2010 were assessed with both PET/CT and conventional studies. Discordance with PET/CT and conventional studies were evaluated, and changes in the management strategy were assessed for each stage. Discordant findings were verified by using intraoperative examination, pathology reports, and follow-up imaging studies.

Results

Multidetector computed tomography (MDCT) and PET/CT showed similar accuracy in detecting lymph node metastasis in patients with clinical stage III (36.2% vs. 42%, P = 0.822) and stage IV (60.3% vs. 63.5%, P = 0.509) disease. PET/CT led to a change in management strategy for 1 of 40 patients (2.5%) with clinical stage I, 0 of 25 patients (0%) with stage II, 9 of 138 patients (6.5%) with stage III, and 8 of 63 patients (12.7%) with stage IV disease.

Conclusion

PET/CT changed the management plan in 6.5% of patients with clinical stage III and 12.7% of patients with clinical stage IV colon cancer. Our findings suggest that PET/CT may be considered as a routine staging tool for clinical stage III and IV colon cancers.

[Importance of PET/CT for imaging of colorectal cancer]

CLINICAL/METHODICAL ISSUE

Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) has emerged as a very useful imaging modality in the management of colorectal carcinoma. Data from the literature regarding the role of PET/CT in the initial diagnosis, staging, radiotherapy planning, response monitoring and surveillance of colorectal carcinoma is presented. Future directions and economic aspects are discussed.

STANDARD RADIOLOGICAL METHODS

Computed tomography (CT), magnetic resonance imaging (MRI) and FDG-PET for colorectal cancer and endorectal ultrasound for rectal cancer.

METHODICAL INNOVATIONS

Combined FDG-PET/CT.

PERFORMANCE

While other imaging modalities allow superior visualization of the extent and invasion depth of the primary tumor, PET/CT is most sensitive for the detection of distant metastases of colorectal cancer.

ACHIEVEMENTS

We recommend a targeted use of PET/CT in cases of unclear M staging, prior to metastasectomy and in suspected cases of residual or recurrent colorectal carcinoma with equivocal conventional imaging. The role of PET/CT in radiotherapy planning and response monitoring needs to be determined. Currently there is no evidence to support the routine use of PET/CT for colorectal screening, staging or surveillance.

PRACTICAL RECOMMENDATIONS

To optimally exploit the synergy between morphologic and functional information, FDG-PET should generally be performed as an integrated FDG-PET/CT with a contrast-enhanced CT component in colorectal carcinoma.