Clinical value of whole-body emission tomography in potentially curable colorectal liver metastases

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.

Integrating respiratory-gated PET-based target volume delineation in liver SBRT planning, a pilot study

Background

To assess the feasibility and benefit of integrating four-dimensional (4D) Positron Emission Tomography (PET) – computed tomography (CT) for liver stereotactic body radiation therapy (SBRT) planning.

Methods

8 patients with 14 metastases were accrued in the study. They all underwent a non-gated PET and a 4D PET centered on the liver. The same CT scan was used for attenuation correction, registration, and considered the planning CT for SBRT planning. Six PET phases were reconstructed for each 4D PET. By applying an individualized threshold to the 4D PET, a Biological Internal Target Volume (BITV) was generated for each lesion. A gated Planning Target Volume (PTVg) was created by adding 3 mm to account for set-up margins. This volume was compared to a manual Planning Target Volume (PTV) delineated with the help of a semi-automatic Biological Target Volume (BTV) obtained from the non-gated exam. A 5 mm radial and a 10 mm craniocaudal margins were applied to account for tumor motion and set-up margins to create the PTV.

Results

One undiagnosed liver metastasis was discovered thanks to the 4D PET. The semi-automatic BTV were significantly smaller than the BITV (p = 0.0031). However, after applying adapted margins, 4D PET allowed a statistically significant decrease in the PTVg as compared to the PTV (p = 0.0052).

Conclusions

In comparison to non-gated PET, 4D PET may better define the respiratory movements of liver targets and improve SBRT planning for liver metastases. Furthermore, non respiratory-gated PET exams can both misdiagnose liver metastases and underestimate the real internal target volumes.

Clinical application of 18F-fluorodeoxyglucose positron emission tomography for assessment and evaluation after therapy for malignant hepatic tumor

Positron emission tomography (PET) is widely available and its application with 2-[(18)F] fluoro-2-deoxy-D-glucose ((18)F-FDG) in oncology has become one of the standard imaging modalities in diagnosing and staging of tumors, and monitoring the therapeutic efficacy in hepatic malignancies. Recently, investigators have measured glucose utilization in liver tumors using (18)F-FDG and positron emission tomography/computer tomography (PET/CT) in order to establish a diagnosis of tumors, assess their biologic characteristics and predict therapeutic effects on hepatic malignancies. The PET/CT with (18)F-FDG may further enhance the hepatic malignancy diagnostic algorithm by accurate diagnosis, staging, restaging and evaluating its biological characteristics, which can benefit the patients suffering from primary and metastatic hepatic tumors such as hepatocellular carcinoma (HCC), cholangiocarcinoma (CCC), and metastatic liver tumor.

Impact of a new respiratory amplitude-based gating technique in evaluation of upper abdominal PET lesions

PET acquisition requires several minutes which can lead to respiratory motion blurring, to increase partial volume effect and SUV under-estimation. To avoid these artifacts, conventional 10-min phase-based respiratory gating (PBRG) can be performed but is time-consuming and difficult with a non-compliant patient. We evaluated an automatic amplitude-based gating method (AABG) which keeps 35% of the counts at the end of expiration to minimize respiratory motion. We estimated the impact of AABG on upper abdominal lesion detectability, quantification and patient management.

METHODS

We consecutively included 31 patients (82 hepatic and 25 perihepatic known lesions). Each patient underwent 3 acquisitions on a Siemens Biograph mCT (4 rings and time-of-flight): a standard free-breathing whole-body (SWB, 5-7 steps/2.5 min per step, 3.3±0.4 MBq/kg of 18F-FDG), a 10-min PBRG with six bins and a 5-min AABG method. All gated acquisitions were performed with an ANZAI respiratory gating system. SUVmax and target to background ratio (TBR, defined as the maximum SUV of the lesion divided by the mean SUV of a region of interest drawn in healthy liver) were compared.

RESULTS

All 94 lesions in SWB images were detected in the gated images. 10-min PBRG and 5-min AABG acquisitions respectively revealed 9 and 13 new lesions and relocated 7 and 8 lesions. Four lesions revealed by 5-min AABG were missed by 10-min PBRG in 3 non-compliant patients. Both gated methods failed to relocate 2 lesions seen on SWB acquisition. Compared to SWB, TBR increased significantly with 10-min PBRG and with 5-min AABG (respectively 41±59%, p=4.10-3 and 66±75%, p=6.10-5) whereas SUVmax did not (respectively 14±43%, p=0.29 with 10-min PBRG, and 24±46%, p=0.11 with 5-min AABG).

CONCLUSION

The AABG is a fast and a user-friendly respiratory gating method to increase detectability and quantification of upper abdominal lesions compared to the conventional PBRG procedure and the SWB acquisition.

Predictors of initial 18F-fluorodeoxyglucose-positron emission tomography indication among patients with colorectal cancer

OBJECTIVES

To evaluate the determinants of initial F-fluorodeoxyglucose (F-FDG)-PET indication following primary colorectal cancer diagnosis among patients who underwent surgery between January 2000 and December 2007 and who were observed at a single institution for at least 2 years after diagnosis.

METHODS

Of the 530 patients who underwent colorectal cancer resection, 113 patients received at least one F-FDG-PET following diagnosis. Outcome variables included indication and time of the first F-FDG-PET following diagnosis. Potential predictors included disease-level and patient-level characteristics. Univariate and multivariate regression analyses were performed.

RESULTS

Patients diagnosed later in the study period and patients with higher-stage disease were more likely to receive their first F-FDG-PET for initial staging (P<0.001 and P=0.016, respectively). Patients with lower-stage disease were more likely to receive their initial F-FDG-PET for suspected recurrence on conventional imaging. When performed more than 2 years after diagnosis, F-FDG-PET was more likely to be ordered for suspected recurrence either on the basis of conventional imaging or on the basis of patient symptoms/tumor markers (P=0.003 and 0.031, respectively). F-FDG-PET demonstrated disease progression in at least 50% of patients referred for each indication (P=0.037).

CONCLUSION

Higher utilization of F-FDG-PET may be appropriate among patients referred for a number of indications including: initial staging, particularly among those with higher-stage disease; suspected recurrence on conventional imaging among patients with lower-stage disease; and suspected recurrence more than 2 years after diagnosis. Further research is needed to verify these findings.

Pretargeted immuno-PET of CEA-expressing intraperitoneal human colonic tumor xenografts: a new sensitive detection method

BACKGROUND

In this study, pretargeted immuno-positron-emission tomography [PET] with a bispecific monoclonal anti-carcinoembryonic antigen [CEA] (CEACAM5) × anti-hapten antibody (bispecific monoclonal antibody [bsmAb]) and a small (1.5 kD) peptide labeled with 68Ga was compared to fludeoxyglucose [18F-FDG]-PET for detecting intraperitoneal [i.p.] CEA-expressing human colonic tumor xenografts in nude mice.

METHODS

Two groups of female BALB/c nude mice were inoculated with LS174T human colonic tumor cells i.p. One group received 5 MBq 18F-FDG, and the other received intravenous injections of the bsmAb, followed 16 h later with 5 MBq of 68Ga-labeled peptide. One hour after the radiolabeled peptide or FDG was given, micro-PET/computed tomography images were acquired. Thereafter, the uptake of the 68Ga or 18F in dissected tissue was determined.

RESULTS

Within 1 h, high uptake of the 68Ga-labeled peptide in the tumor lesions (23.4 ± 7.2% ID/g) and low background activity levels were observed (e.g., tumor-to-intestine ratio, 58 ± 22). This resulted in a clear visualization of all intra-abdominal tumor lesions ≥ 10 μL and even some tumors as small as 5 μL (2 mm diameter). 18F-FDG efficiently localized in the tumors (8.7 ± 3.1% ID/g) but also showed physiological uptake in various normal tissues (e.g., tumor-to-intestine ratio, 3.9 ± 1.1).

CONCLUSIONS

Pretargeted immuno-PET with bsmAb and a 68Ga-labeled peptide could be a very sensitive imaging method for imaging colonic cancer, disclosing occult lesions.

What is the most accurate whole-body imaging modality for assessment of local and distant recurrent disease in colorectal cancer? A meta-analysis : imaging for recurrent colorectal cancer

PURPOSE

The objective of this study was to compare the diagnostic performance of positron emission tomography (PET), PET/CT, CT and MRI as whole-body imaging modalities for the detection of local and/or distant recurrent disease in colorectal cancer (CRC) patients who have a (high) suspicion of recurrent disease, based on clinical findings or rise in carcinoembryonic antigen (CEA).

METHODS

A meta-analysis was undertaken. PubMed and Embase were searched for studies on the accuracy of whole-body imaging for patients with suspected local and/or distant recurrence of their CRC. Additionally, studies had to have included at least 20 patients with CRC and 2 × 2 contingency tables had to be provided or derivable. Articles evaluating only local recurrence or liver metastasis were excluded. Summary receiver-operating characteristic (ROC) curves were constructed from the data on sensitivity and specificity of individual studies and pooled estimates of diagnostic odds ratios (DORs) and areas under the ROC curve (AUCs) were calculated. To test for heterogeneity the Cochran Q test was used.

RESULTS

Fourteen observational studies were included which evaluated PET, PET/CT, CT and/or MRI. Study results were available in 12 studies for PET, in 5 studies for CT, in 5 studies for PET/CT and in 1 study for MRI. AUCs for PET, PET/CT and CT were 0.94 (0.90-0.97), 0.94 (0.87-0.98) and 0.83 (0.72-0.90), respectively. In patient based analyses PET/CT had a higher diagnostic performance than PET with an AUC of 0.95 (0.89-0.97) for PET/CT vs 0.92 (0.86-0.96) for PET.

CONCLUSION

Both whole-body PET and PET/CT are very accurate for the detection of local and/or distant recurrent disease in CRC patients with a (high) suspicion of recurrent disease. CT has the lowest diagnostic performance. This difference is probably mainly due to the lower accuracy of CT for detection of extrahepatic metastases (including local recurrence). For clinical practice PET/CT might be the modality of choice when evaluating patients with a (high) suspicion of recurrent disease, because of its best performance in patient based analyses and confident prediction of disease status.

PET-CT in radiation oncology: the impact on diagnosis, treatment planning, and assessment of treatment response

OBJECTIVE

To review the role of hybrid positron emission tomography (PET)-computed tomography (CT) systems in the design and management of cancer patients in the modern radiation oncology practice. PET is co-registered with CT and incorporated into a systematic approach to the staging, management, and assessment of response and surveillance of a variety of oncologic diagnoses.

METHODS

A review of the literature of functional imaging such as PET-CT in staging, treatment plan design, assessment of response and detection of recurrence for tumors involving the head and neck, lung, esophagus, rectum amongst others.

RESULTS

PET and PET-CT offer significant advantages which include more accurate staging which often results in management changes in roughly one-third of patients across a number of disease site. More accurate target definition may augment highly conformal radiation treatment plans using intensity-modulated radiation therapy and stereotactic radiosurgery and radiotherapy.

CONCLUSION

The emerging data appears to suggest the functional imaging may be a more useful tool to evaluate the therapeutic effect of treatment, detect early failures and prognosticate long-term outcome.

Optimizing the approach to patients with potentially resectable liver metastases from colorectal cancer

Liver metastases are a common event in colorectal carcinoma. Significant advances have been made in managing these patients in the last decade, including improvements in staging and surgical techniques, an increasing armamentarium of chemotherapeutics and multiple local ablative techniques. While combination chemotherapy significantly improves median patient survival, surgical resection provides the only prospect of cure and is the focus of this review. Interpretation of published work in this field is challenging, particularly as there is no consensus to what is resectable disease. Of particular interest recently has been the use of neoadjuvant treatment for downstaging and downsizing disease in patients with initially unresectable liver metastases, in the hope of response leading to potentially curative surgery. This review summarizes the recent developments and consensus guidelines in the areas of staging, chemotherapy, local ablative techniques, radiation therapy and surgery, emphasizing the multidisciplinary approach to this disease and ongoing controversies in this field and examines the changing paradigms in the management of colorectal hepatic metastases.

Intraoperative sonography in patients with colorectal cancer and resectable liver metastases on preoperative FDG-PET-CT

BACKGROUND

Combined fluorine 18-fluorodeoxyglucose-positron emission tomography-CT imaging has been shown to be of good diagnostic value in the preoperative evaluation of patients with colorectal cancer and liver metastases. The adjunctive use of intraoperative sonography (IOUS) may have a limited impact on treatment selection in these patients.

PURPOSE

To compare the diagnostic performance of preoperative positron emission tomography (PET)-CT alone and PET-CT combined with IOUS in the evaluation of patients who are considered for curative resection of hepatic metastases from colorectal carcinoma.

MATERIALS AND METHODS

Patients with colorectal cancer who underwent resection of hepatic metastases and preoperative PET-CT (with or without contrast-enhanced CT) and IOUS were identified. The performance of the imaging techniques was evaluated through review of the radiologic reports, correlation with surgical and histopathologic findings, and clinical follow-up.

RESULTS

Thirty-one patients (mean age, 63.5 years [range, 53-82 years]) were analyzed. Fifteen patients had received preoperative chemotherapy. The mean interval between PET-CT and IOUS was 22.6 days (range, 1-56 days). In 4 cases, neither PET-CT nor IOUS correctly diagnosed the liver metastases. In all 31 patients, the sensitivity of PET-CT alone and PET-CT combined with IOUS was 63% (95% CI 44-80%) and 93% (95% CI 78-98%), respectively; the positive predictive value was 81% and 89%, respectively. In patients without preoperative chemotherapy (n = 16), the sensitivity of PET-CT alone and PET-CT combined with IOUS was 77% (95% CI 49-94%) and 100% (95% CI 79-100%), respectively. In 11 cases (35%), IOUS altered the surgical strategy.

CONCLUSION

In patients with colorectal carcinoma and potentially resectable liver metastases on preoperative PET-CT, IOUS can provide additional information that may alter decision making with regard to surgical technique.

Positron Emission Tomography Detection of Distant Metastatic or Synchronous Disease in Patients with Locally Advanced Rectal Cancer Receiving Preoperative Chemoradiation

BACKGROUND

Patients with locally advanced rectal cancer may present with synchronous distant metastases. Choice of optimal treatment--neoadjuvant chemoradiation versus systemic chemotherapy alone--depends on accurate assessment of distant disease. We prospectively evaluated the ability of [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) to detect distant disease in patients with locally advanced rectal cancer who were otherwise eligible for combined modality therapy (CMT).

METHODS

Ninety-three patients with locally advanced rectal cancer underwent whole-body [18F]FDG PET scanning 2-3 weeks before starting CMT. Sites other than the rectum, mesorectum, or the area along the inferior mesenteric artery were considered distant and were divided into nine groups: neck, lung, mediastinal lymph node (LN), abdomen, liver, colon, pelvis, peripheral LN, and soft tissue. Two nuclear medicine physicians blinded to clinical information used PET images and a five-point scale (0-4) to determine certainty of disease. A score greater than 3 was considered malignant. Confirmation was based on tissue diagnosis, surgical exploration, and subsequent imaging.

RESULTS

At a median follow-up of 34 months, the overall accuracy, sensitivity, and specificity of PET in detecting distant disease were 93.7%, 77.8%, and 98.7% respectively. Greatest accuracy was demonstrated in detection of liver (accuracy = 99.9%, sensitivity = 100%, specificity = 98.8%) and lung (accuracy = 99.9%, sensitivity = 80%, specificity = 100%) disease; PET detected 11/12 confirmed malignant sites in liver and lung. A total of 10 patients were confirmed to have M1 stage disease. All 10 were correctly staged by pre-CMT PET; abdominopelvic computed tomography (CT) scans accurately detected nine of them.

CONCLUSION

Baseline PET in patients with locally advanced rectal cancer reliably detects metastatic disease in liver and lung. PET may play a significant role in defining extent of distant disease in selected cases, thus impacting the choice of neoadjuvant therapy.

Radiological staging of colorectal liver metastases

Rapid advances in imaging technology have improved the detection, characterization and staging of colorectal liver metastases. Multi-modality imaging approach is usually the more useful in staging colorectal liver metastases. Multi-detector computed tomography (MDCT) remains the main imaging modality for preoperative planning, lesion detection and tumour surveillance. Magnetic resonance imaging (MRI) and contrast enhanced ultrasonography (US) are invaluable in problem solving for characterization indeterminate lesions, while contrast enhanced intra-operative ultrasound (CE-IOUS) may be the new gold standard staging tool prior to liver resection. Ultimately, the imaging strategy has to be tailored to the clinical situation to obtain the most relevant information for optimal use of available imaging resources.

The role of FDG-PET in the selection of patients with colorectal liver metastases

BACKGROUND

Selection of patients for hepatic resection of colorectal liver metastases is still limited. After conventional work up by computed tomography (CT) scan, 60% of patients will develop recurrent disease in the early years after resection. The aim of the present study was to evaluate whether an additional fluorine-18-deoxyglucose positron emission tomography (FDG-PET) improves patient selection and therefore adds value to select patients for curative liver resection.

METHODS

Data from 203 patients selected for surgical treatment of colorectal liver metastases between 1995 and 2003 were collected in a prospective database. Group A consisted of 100 consecutive patients selected for hepatic surgery by conventional diagnostic imaging (CT chest and abdomen) only. Group B consisted of 103 consecutive patients selected for hepatic surgery by conventional diagnostic methods plus an additional FDG-PET.

RESULTS

The number of patients with futile surgery, in which further treatment was considered inappropriate at laparotomy, was 28.0% in group A and 19.4% in group B. The reason for unresectable disease differed between groups. In group A, 10/100 (10.0%) patients showed extrahepatic abdominal disease versus 2/103 patients (1.9%) in group B (P = .017). In all other cases, resection was not performed because liver disease proved too extensive at laparotomy. For patients ultimately undergoing surgical treatment of the metastases, survival was comparable between groups. Overall survival at 3 years was 57.1% in group A versus 60.1% in group B. Disease-free survival at 3 years was 23.0% in group A and 31.4% in group B.

CONCLUSIONS

In patients with colorectal liver metastases, FDG-PET may reduce the number of negative laparotomies. However, the effect size on the selection of these patients seems not sufficient enough to affect the overall and disease-free survival after treatment.

Correlation of GLUT-1 overexpression, tumor size, and depth of invasion with 18F-2-fluoro-2-deoxy-D-glucose uptake by positron emission tomography in colorectal cancer

We investigated the wide variability of 18F-2-fluoro-2-deoxy-D: -glucose (FDG) uptake, semiquantified as standardized uptake value (SUV), in positron emission tomography (PET) scanning, in 20 patients with colorectal cancer (CRC), including 1 with synchronous hepatic metastasis. The sensitivity of PET in CRC diagnosis was 100%, with a mean SUV of 8.0 (3.1-11.9). Tumor size and depth of invasion were associated with higher SUVs (P=.0004, .042, respectively). Strong glucose transporter-1 (GLUT-1) expression had significantly positive correlation with the SUV (r=.619, P=.003). GLUT-1 expression revealed positive staining in 17 (85%) of the 20 primary lesions. The central part of the tumor, thought to be relatively hypoxic, had stronger GLUT-1 expression and a higher SUV than the periphery, in both the primary tumor and hepatic metastatic foci. Our data suggest that the SUVs of FDG uptake in PET may be a noninvasive biomarker for advanced CRC, indicative of a large hypoxic tumor with deep invasion.

Comparison of Multiphase CT, FDG-PET and Intra-Operative Ultrasound in Patients with Colorectal Liver Metastases Selected for Surgery

BACKGROUND

For patients with colorectal liver metastases, resection is the treatment of choice. Careful selection of these patients is crucial in order to reduce the chance of unexpected findings at laparotomy and abandoning further surgical intervention. Here, we evaluate the predictive value of CT and FDG-PET of the liver and extrahepatic findings compared to findings during laparotomy and 6 months follow-up.

METHODS

131 consecutive patients, selected for hepatic surgery for colorectal liver metastases by CT and FDG-PET, were evaluated prospectively. During surgery, the liver was assessed by intra-operative ultrasound, palpation and histology.

RESULTS

In 127 patients (97%), CT was true-positive for liver metastases. In 3 patients, CT was false-positive and in 1 patient false-negative. In 126 patients (96%), FDG-PET was true-positive for liver metastases, in 2 patients FDG-PET was false-negative, in 3 patients true-negative (negative FDG-PET, false-positive CT). At laparotomy a total of 363 liver metastases was identified: 63 lesions <10 mm [10 (16%) detected by both CT and FDG-PET], 172 lesions of 10-20 mm [123 (72%) CT-positive, 129 (75%) by FDG-PET-positive], and 28 lesions >20 mm [124 (97%) CT-positive, 121 (95%) FDG-PET-positive]. CT and FDG-PET missed approximately 30% of the smaller liver lesions, resulting in a significant change in clinical management during surgery in only nine patients.

CONCLUSIONS

CT and FDG-PET have a similar diagnostic yield for the identification of liver metastases; both modalities being adequate on a patient-basis but inadequate to detect the smallest of liver lesions. However, the clinical relevance of the latter is limited.

The role of 18F-fluoro-deoxy-glucose positron emission tomography (FDG-PET) in the management of patients with colorectal cancer

AIM

In patients with colorectal cancer an accurate diagnostic work-up is mandatory in order to perform the most specific treatment. At this moment 18F-fluoro-deoxy-glucose positron emission tomography (FDG-PET) is considered an accurate imaging technique in staging/restaging several malignancies. The aim of this paper is to review the scientific literature available about the role of FDG-PET in the management of patients with colorectal cancer.

METHODS

An overview on Medline of scientific literature concerning FDG-PET and colorectal cancer was performed. The most relevant studies are reported. Advantages, limitations and new chances in using FDG-PET in these subsets of patients are summarized.

RESULTS

FDG-PET is a useful tool in the evaluation of colorectal cancer. In comparison to conventional imaging technique, FDG-PET has an additional diagnostic value because it allows to metabolically characterize undetermined lesions suspected for recurrence of disease, to perform a complete pre-surgical staging and to identify occult metastatic disease. In clinical practice its use leads to a change in therapeutic choices in a high percentage of cases.

CONCLUSIONS

FDG-PET should be considered an essential diagnostic tool in the management of patients with colorectal cancer, especially in recurrent disease evaluation.

FDG-PET in colorectal cancer

[18F]Fluorodeoxyglucose (FDG) positron emission tomography (PET) is a useful imaging tool in the evolving management of patients with colorectal carcinoma. This technique is able to measure and visualize metabolic changes in cancer cells. This feature results in the ability to distinguish viable tumor from scar tissue, in the detection of tumor foci at an earlier stage than possible by conventional anatomic imaging and in the measurement of alterations in tumor metabolism, indicative of tumor response to therapy. Nowadays, FDG-PET plays a pivotal role in staging patients before surgical resection of recurrence and metastases, in the localization of recurrence in patients with an unexplained rise in serum carcinoembryonic antigen and in assessment of residual masses after treatment. In the presurgical evaluation, FDG-PET may be best used in conjunction with anatomic imaging in order to combine the benefits of both anatomical (CT) and functional (PET) information, which leads to significant improvements in preoperative liver staging and preoperative judgment on the feasibility of resection. Integration of FDG-PET into the management algorithm of these categories of patients alters and improves therapeutic management, reduces morbidity due to futile surgery, leads to substantial cost savings and probably also to a better patient outcome. FDG-PET also appears to have great potential in monitoring the success of local ablative therapies soon after intervention and in the prediction and evaluation of response to radiotherapy, systemic therapy, and combinations thereof. This review aims to outline the current and future role of FDG-PET in the field of colorectal cancer.

An update on imaging of colorectal cancer

Screening of asymptomatic average-risk patients for presence of colon cancer and early detection in precursor stages is of great interest to general population. Comprehensive evaluation of symptomatic or high-risk patients represents another important clinical focus. Available techniques for total colon imaging, rectal cancer staging and the role of positron emission tomography are discussed.

Positron emission tomography scanning is not superior to whole body multidetector helical computed tomography in the preoperative staging of colorectal cancer

BACKGROUND

The role of positron emission tomography with the glucose analogue [18F] fluoro-2-deoxy-D-glucose (FDG-PET) in the initial staging of disease in patients with primary colorectal cancer (CRC) has not been adequately assessed.

AIMS

To evaluate the additional value of FDG-PET as a staging modality, complementary to routine multidetector row computed tomography (MDCT) in patients with CRC.

METHODS

Forty four patients with CRC underwent preoperative MDCT and FDG-PET. The accuracy of intraoperative macroscopic staging was also investigated compared with histopathological diagnosis. All FDG-PET images were evaluated with respect to detectability of the primary tumour, lymph node involvement, and distant metastases. Both MDCT and FDG-PET diagnoses and treatment plan were compared with surgical and histopathological results.

RESULTS

Thirty seven patients underwent surgery. Tumour detection rate was 95% (42/44) for MDCT, 100% (44/44) for FDG-PET, and 100% (37/37) for intraoperative macroscopic diagnosis. Pathological diagnosis of T factor was T1 in five, T2 in four, T3 in 24, and T4 in four cases. Concordance rate with pathological findings of T factor was 57% (21/37) for MDCT and 62% (23/37) for macroscopic diagnosis. Lymph node involvement was pathologically positive in 19 cases. Regarding N factor, overall accuracy was 62% (23/37) for MDCT, 59% (22/37) for FDG-PET, and 70% (26/37) for macroscopic diagnosis. For all 44 patients, FDG-PET findings resulted in treatment changes in only one (2%) patient.

CONCLUSION

FDG-PET is not superior to routine MDCT in the initial staging of primary CRC.

Is routine magnetic resonance imaging justified for the early detection of resectable liver metastases from colorectal cancer?

PURPOSE

This study was designed to determine whether routine follow-up by magnetic resonance imaging improves the detection of resectable liver metastases from colorectal cancer and patients' survival.

METHODS

Patients who underwent curative surgery for colorectal cancer were included in a program of liver surveillance by routine magnetic resonance imaging, in addition to the standard follow-up protocol consisting of clinical examination and biochemical tests. The median follow-up was 41 (interquartile range, 30-53) months, with a median magnetic resonance imaging surveillance period of 20 (interquartile range, 12-27) months. Cases were analyzed for mode of diagnosis, resectability, and overall survival.

RESULTS

Liver metastases were found in 37 (13 percent) of 293 patients studied. Magnetic resonance imaging diagnosed hepatic metastases with 84 percent sensitivity and 90 percent specificity. In 28 (76 percent) patients, carcinoembryonic antigen and/or liver function tests were abnormally elevated and 5 patients (14 percent) were symptomatic. Hepatic resection was possible in only nine patients (24 percent). Magnetic resonance imaging detected all resectable cases, whereas traditional follow-up would have missed three (33 percent) cases suitable for surgery.

CONCLUSIONS

Although magnetic resonance imaging surveillance increased the number of patients suitable for liver resection by 50 percent, these represented only 1 percent of the patients included in the study. Whether these results are enough to justify the allocation of expensive resources is controversial.

PET imaging for evaluation of metastatic colorectal cancer of the liver

Colorectal cancer is a major cause of cancer death in Western Europe and United States; the liver is the most common site for colorectal metastases. PET has an important role in the management of patients with colorectal liver metastases. It is an effective tool to detect hepatic metastases and to monitor the response to systemic and local therapy. The major impact of PET-CT over PET alone is the improvement in the certainty of lesion location. PET-CT has the unique advantage to combine functional and anatomic imaging in an integrated scanner; it allows a thoroughly evaluation of patients with colorectal liver metastases.

Gastrointestinal malignancies evaluated with (18)F-fluoro-2-deoxyglucose positron emission tomography

(18)F-fluoro-2-deoxyglucose positron emission tomography has demonstrated high accuracy in the staging and evaluation of colorectal and esophageal carcinomas. FDG PET is demonstrating increasing utility in a number of other gastrointestinal tumours and clinical scenarios. The established clinical indications for its use, the diagnostic accuracy, and limitations will be reviewed. Data on the emerging indications and limitations for pancreatic, hepatocellular, and gastric carcinomas, as well as gastrointestinal stromal tumours, cholangiocarcinoma, and carcinoma of unknown primary will also be briefly discussed. The use of combined PET-CT is demonstrating further improvements in diagnostic accuracy.

The impact of fluor-18-deoxyglucose-positron emission tomography in the management of colorectal liver metastases

Fluor-18-deoxyglucose-positron emission tomography (FDG-PET) has emerged as a promising diagnostic modality in recurrent colorectal carcinoma. Whole-body FDG-PET may be an accurate diagnostic modality to determine whether patients with recurrent hepatic disease are suitable candidates for curative resection. Reports on the use of FDG-PET in patients with recurrent colorectal carcinoma are scarce, especially those on colorectal liver metastases. To assess the usefulness of this emerging modality for the selection of patients to undergo resection for colorectal liver metastases, a systematic (meta)-analysis of the current literature was conducted. In the absence of randomized controlled clinical trials, a traditional meta-analysis could not be performed. An alternative strategy was designed to evaluate the current literature. After a literature search, an index score was devised to evaluate the articles with regard to the impact of FDG-PET in patients with colorectal liver metastases. The index scored articles on several items and, as such, could be considered an objective approach for the assessment of diagnostic, nonrandomized clinical trials. The proposed index proved to be an independent instrument for judging several research questions and was used systematically to address the sensitivity, specificity, and clinical impact of FDG-PET in patients with colorectal liver metastases. For FDG-PET, the pooled sensitivity and specificity results were 88.0% and 96.1%, respectively, for hepatic disease and 91.5% and 95.4%, respectively, for extrahepatic disease. For the 6 articles that reported the highest scores on the index, the sensitivity and specificity of FDG-PET for hepatic metastatic disease were 79.9% and 92.3%, respectively, and 91.2% and 98.4%, respectively, for extrahepatic disease, respectively. For computed tomography, the pooled sensitivity and specificity results were 82.7% and 84.1%, respectively, for hepatic lesions and 60.9% and 91.1%, respectively, for extrahepatic lesions. The percentage change in clinical management due to FDG-PET was 31.6% (range, 20.0-58.0%) in the articles that scored above the mean and reported this item. For the 6 highest scoring studies, the percentage change in clinical management was 25.0% (range, 20.0-32.0%). Despite apparent omissions in the literature, the combined sensitivity and specificity of FDG-PET clearly indicated that FDG-PET has added value in the diagnostic workup of patients with colorectal liver metastases. FDG-PET can be considered a useful tool in preoperative staging and produced superior results compared with conventional diagnostic modalities, especially for excluding or detecting extrahepatic disease.

Applications of PET in Liver Imaging

Fluorodeoxyglucose PET (FDG-PET) imaging has an important role in determining if there are metastases to the liver and whether disease has spread beyond the liver. Such information is critical for planning surgical resections of liver metastases. The ability of FDG-PET quantitatively to estimate metabolic rates makes it an important tool for monitoring. With increasingly broad indications for FDG-PET imaging, it is expected that FDG-PET (and PET-CT) of the liver will play a growing and increasingly important role in detecting and monitoring treatment of tumors involving the liver.

Does the novel PET/CT imaging modality impact on the treatment of patients with metastatic colorectal cancer of the liver?

OBJECTIVE

To compare the diagnostic value of contrast-enhanced CT (ceCT) and 2-[18-F]-fluoro-2-deoxyglucose-PET/CT in patients with metastatic colorectal cancer to the liver.

BACKGROUND

Despite preoperative evaluation with ceCT, the tumor load in patients with metastatic colorectal cancer to the liver is often underestimated. Positron emission tomography (PET) has been used in combination with the ceCT to improve identification of intra- and extrahepatic tumors in these patients. We compared ceCT and a novel fused PET/CT technique in patients evaluated for liver resection for metastatic colorectal cancer.

METHODS

Patients evaluated for resection of liver metastases from colorectal cancer were entered into a prospective database. Each patient received a ceCT and a PET/CT, and both examinations were evaluated independently by a radiologist/nuclear medicine physician without the knowledge of the results of other diagnostic techniques. The sensitivity and the specificity of both tests regarding the detection of intrahepatic tumor load, extra/hepatic metastases, and local recurrence at the colorectal site were determined. The main end point of the study was to assess the impact of the PET/CT findings on the therapeutic strategy.

RESULTS

Seventy-six patients with a median age of 63 years were included in the study. ceCT and PET/CT provided comparable findings for the detection of intrahepatic metastases with a sensitivity of 95% and 91%, respectively. However, PET/CT was superior in establishing the diagnosis of intrahepatic recurrences in patients with prior hepatectomy (specificity 50% vs. 100%, P = 0.04). Local recurrences at the primary colo-rectal resection site were detected by ceCT and PET/CT with a sensitivity of 53% and 93%, respectively (P = 0.03). Extrahepatic disease was missed in the ceCT in one third of the cases (sensitivity 64%), whereas PET/CT failed to detect extrahepatic lesions in only 11% of the cases (sensitivity 89%) (P = 0.02). New findings in the PET/CT resulted in a change in the therapeutic strategy in 21% of the patients.

CONCLUSION

PET/CT and ceCT provide similar information regarding hepatic metastases of colorectal cancer, whereas PET/CT is superior to ceCT for the detection of recurrent intrahepatic tumors after hepatectomy, extrahepatic metastases, and local recurrence at the site of the initial colorectal surgery. We now routinely perform PET/CT on all patients being evaluated for liver resection for metastatic colorectal cancer.

Prospective evaluation of the impact of [18F]fluoro-2-deoxy-d-glucose positron emission tomography of resectable colorectal liver metastases

Background

The aim of this study was to assess the additional value of information provided by positron emission tomography (PET) with [18F]fluoro-2-deoxy-d-glucose (FDG) over that provided by computed tomography (CT) in patients with resectable liver metastases from colorectal cancer.

Methods

Between October 2001 and November 2002, a prospective double-blind comparison of preoperative FDG-PET and thoracoabdominal CT was performed in 53 patients with potentially resectable liver metastases from colorectal cancer. All resected metastases were subjected to histological examination.

Results

Histological examination confirmed the presence of malignant or benign lesions detected by PET and/or CT in 95 per cent of instances. Overall sensitivity (78 per cent) and accuracy (88 per cent) of PET were equivalent to those of CT (76 and 86 per cent respectively). The sensitivity of PET was equivalent to that of CT for hepatic sites (both 79 per cent), but was superior for extrahepatic abdominal sites (63 and 25 per cent respectively). PET provided additional information in five patients, mainly by revealing abdominal extrahepatic metastases, but falsely upstaged three patients.

Conclusion

Whole-body FDG-PET may identify unrecognized extrahepatic metastases in patients with potentially resectable liver metastases imaged by CT. However, additional information provided by PET is not as reliable as suggested by earlier retrospective studies.

Long-term Survival of Patients with Unresectable Colorectal Liver Metastases treated by Percutaneous Interstitial Laser Thermotherapy

In situ ablation of colorectal cancer (CRC) liver metastases is an accepted form of treatment for selected patients. It is associated with low morbidity and mortality and increases the number of patients who may benefit from therapy compared to resection alone. This study assesses the impact of interstitial laser thermotherapy (ILT) on local tumor control and long-term survival in patients with unresectable CRC liver metastases. Percutaneous ILT was performed in patients with unresectable CRC liver metastases between January 1992 and December 1999 using a bare-tip quartz fiber connected to an Nd:YAG laser source. This was prior to the routine use of a diffusing fiber for ablative therapy. Treatment was monitored with real-time ultrasonography. Tumors were considered unresectable based on their anatomic location or the extent of liver involvement. Patients with extrahepatic disease, more than five liver metastases, or tumors larger than 10 cm in diameter were excluded from this study. Local tumor control was assessed by dynamic computed tomography (CT) 6 months after therapy. Long-term follow-up was undertaken, and the impact of various factors on survival was analyzed. Eighty patients with a mean age of 63.8 years were suitable for ILT. In total, 168 liver tumors with a median diameter of 5 cm (range 1-10 cm) were so treated. There were no procedure-related deaths. The overall complication rate was 16%, with all cases managed conservatively. Bradycardia (n = 5), pneumothorax (n = 3), and persistent pyrexia (n = 3) were the most common complications. Complete tumor ablation was noted in 67% of patients assessed by CT 6 months following the initial therapy. Median follow-up was 35 months (range 4-96 months), with 10 patients alive at the end of this period. Altogether there were 67 deaths, which were related to hepatic disease in 55 cases and to extrahepatic disease in 9; they were unrelated to malignancy in 3 others. Three patients were excluded from follow-up after ILT down-staging of tumors that allowed complete surgical resection. The median disease-free survival of patients treated by ILT was 24.6 months, with a 5-year survival of 3.8%. Poor tumor differentiation and the presence of more than two hepatic metastases were associated with lower overall survival (p < 0.01). Fourteen patients treated by ILT for postoperative hepatic recurrences had the best outcome, with a median overall survival of 36.3 months and a 5-year survival of 17.2%. Percutaneous ILT is a minimally invasive, safe, effective technique that appears to improve overall survival in specific patients with unresectable CRC liver metastases, compared to the natural history of untreated disease reported in the literature.

Role of FDG-PET in the diagnosis and treatment of colorectal liver metastases

Positron emission tomography (PET) using [(18)F]-2-deoxy-2-fluoro-d-glucose (FDG) has emerged as a promising diagnostic modality in recurrent colorectal cancer. Data in the literature show that the addition of FDG-PET changes disease management in up to 30% of patients with potentially resectable liver metastases, mainly by detecting previously unknown extrahepatic disease. Furthermore, FDG-PET is useful in the follow-up of patients who underwent surgical procedures of the liver, since it is exquisitely sensitive in detecting residual or relapse malignancy in scarred liver tissue following both resection and local ablative techniques. For follow-up during systemic therapy, early FDG-PET appears predictive for response to therapy. However, at present, the available data are insufficient to justify the FDG-PET-driven management of patients treated with chemotherapy. FDG-PET and computerized tomography are complimentary techniques in staging and restaging patients with advanced colorectal cancer. The combination of these two modalities significantly impacts upon patient management.

FDG-PET for the pre-operative evaluation of colorectal liver metastases

INTRODUCTION

This study assesses the accuracy of routine whole body fluorodeoxyglucose-positron emission tomography (FDG-PET) in the pre-operative staging of patients with colorectal liver metastases (CLM).

METHODS

A prospective study of patients referred for hepatic resection was undertaken. Patients were staged by spiral CT and FDG-PET. The results of these investigations were considered independently.

RESULTS

Twenty-eight patients had confirmed CLM. Eleven patients had solitary CLM; 10 of whom were correctly identified by both modalities. In the remaining 17 patients, 10 had multiple CLM and seven had extrahepatic disease. FDG-PET detected all lesions (sensitivity 100%, specificity 91%). CT incorrectly diagnosed solitary CLM in five patients and failed to detect extrahepatic disease in four patients (sensitivity 47%, specificity 91%). FDG-PET resulted in altered management for 12 patients of whom seven avoided inappropriate surgery.

CONCLUSION

FDG-PET is more sensitive and specific for pre-operative staging of CLM. FDG-PET confers clinical benefit through altered patient management.

18F-FDG positron emission tomography staging and restaging in rectal cancer treated with preoperative chemoradiation

PURPOSE

To assess the information supplied by FDG-PET in patients with locally advanced rectal cancer both in the initial staging and in the evaluation of tumor changes induced by preoperative chemoradiation (restaging).

METHODS AND MATERIALS

Twenty-five consecutive patients with rectal cancer were included, with tumor stages (c)T(2-4)N(x)M(0), during the period 1997-1999. We prospectively performed two FDG-PET scans in all patients to assess disease stage (1) at initial diagnosis and (2) presurgically, 4 to 5 weeks after protracted chemoradiation. Protracted chemoradiation was carried out during 5-6 weeks with 45-50 Gy, plus concurrent oral tegafur 1200 mg/day or 5-fluorouracil 500-1000 mg/m(2) administered as a 24-h continuous i.v. infusion on Days 1-4 and 21-25 of the radiotherapy treatment. Tumors were staged with CT in 95% of patients, whereas endorectal ultrasound was used in 90% of patients. Maximum standardized uptake value (SUVmax) was used as the quantitative parameter to estimate the tumor:tissue metabolic ratio.

RESULTS

Preoperative chemoradiation significantly decreased the SUVMAX: 5.9 (mean SUVmax at initial staging) vs. 2.4 (mean SUVmax after chemoradiation) with p < 0.001. Unknown liver metastases were detected by FDG-PET in 2 patients, in 1 of them with the initial staging FDG-PET scan, and with the restaging FDG-PET scan in the other. After an average follow-up of 39 months, the value of SUVmax > or =6 allowed us to discriminate for survival at 3 years: 92% vs. 60% (p = 0.04). T downstaging (total 62%) was significantly correlated with SUVmax changes: 1.9 vs. 3.3 (p = 0.03). The degree of rectal cancer response to chemoradiation, established as mic vs. mac categories, was not associated with SUVmax differences (mean values of 2.0 vs. 2.7).

CONCLUSION

Preliminary results observed suggest the potential utility of FDG-PET as a complementary diagnostic procedure in the initial clinical evaluation (8% of unsuspected liver metastases) as well as in the assessment of chemoradiation response (any T downstaged event) of locally advanced rectal cancer. Initial SUVmax might be of prognostic value related to long-term patient outcome.

The role of positron emission tomography in the management of colorectal cancer

Positron emission tomography (PET) is a functional imaging modality that has made the transition from the research environment to the clinical environment over the last 10 years. Its major role is in the field of oncology where it is being used increasingly in the management of several tumour types including colorectal cancer. This review aims to outline the current and future role of PET scanning in the field of colorectal cancer.

Patterns of failure following curative resection of colorectal liver metastases

AIMS

Several studies have focused on factors determining recurrence and survival rate after curative resection of colorectal liver metastases (LM). Data are lacking with regard to patterns of failure indicating where and when recurrences arise.

METHODS

One-hundred-and-five consecutive patients [F/M: 31/74; mean age 61 years (range 36-80 y)] with primary colorectal liver metastases underwent surgical R0 curative resection between 1990-1999. Patient follow-up was closed in January 2002. The common closing date method was used for survival analysis. Multivariate analysis was performed with the Cox proportional hazard technique.

RESULTS

The overall (OS) vs disease free survival (DFS) rates at 1, 2, and 5 years were 88.5 vs 63.3, 73.4 vs 40.2, and 36.8 vs 18.1%, respectively. Elevated serum CEA level was the only factor independently related to recurrent disease. Elevated serum CEA level, maximum diameter of liver metastases (LM), and satellitosis were factors significantly related to poor OS. Recurrent liver metastases developed in 43% and extra-hepatic metastases in 60% of the patients. In about half of the patients cancer recurrence was observed within 18 months, almost equally distributed between hepatic and extra-hepatic sites.

CONCLUSION

Despite optimal patient selection and curative resection of colorectal liver metastases, more than a half of the patients developed cancer recurrence within 2 years.

Management of colorectal liver metastases

Hepatic metastases occur in 60% of patients following resection for colorectal cancer. Liver resection is the only curative option, with one third of resected patients alive at five years. In those developing recurrence in the liver following resection, further liver surgery may be curative, with similar 5 years survival rates of about 30%. Until recently surgery was feasible in only 15-25% of patients with colorectal liver metastases. New strategies, such as downstaging chemotherapy, portal vein embolization and two-stage hepatectomy, may increase the resectability rate by 15%. Earlier detection of liver metastases would increase resectability, although good follow-up trials are lacking. Once suspected, colorectal liver metastases are staged by spiral CT, CT portography and MRI, which have similar overall accuracies. Mortality following liver resection is less than 5% in major centres, with a morbidity rate of 20% to 50%. Prognostic scoring systems can be used to predict the likely cure rate with resection. Pulmonary metastases occur in 10-25% of patients with resected colorectal cancer, but are limited to the lung in only 2% of cases. In these selected cases surgery provides long-term survival in 20-40%, and repeat lung resection has shown similar rates. For patients with unresectable disease, chemotherapy and ablation techniques have been demonstrated to prolong survival, although chemotherapy alone has been shown to improve quality of life.

FDG-PET improves the management of patients with suspected recurrence of colorectal cancer

This study aims to assess the influence of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) detection of recurrent disease on the management of patients with colorectal cancer and suspected recurrence. One hundred and twenty patients with suspected recurrence were studied with FDG-PET. Fifty-eight patients were referred for FDG-PET because of the elevation of serum tumour markers. Thirty-one patients were referred because of inconclusive results of conventional imaging modalities. Twenty-five patients had known recurrence and were referred for pre-surgical assessment. Six patients were referred because of abdominal pain. A major management change was considered when, as a consequence of FDG-PET results, medical treatment was changed to surgical, or surgical to medical or to no treatment. A minor management change was considered when changes were made within a treatment modality. Of the 58 patients with elevated serum carcinoembryonic antigen (CEA), FDG-PET detected recurrence and led to a major management change in 34 (58%). Eighteen underwent curative surgery and 16 were treated with systemic therapy. Of the 31 patients evaluated because of inconclusive results of conventional imaging modalities, FDG-PET was positive for recurrence in 24 and negative in seven. A major management change took place in 14 patients (45%). Of the 25 patients evaluated to rule out other sites of disease before surgery, FDG-PET did not show any other site of recurrence in 13 (52%) and showed more lesions in the remaining patients. Major management change took place in eight patients (32%). Overall, in the 120 patients studied, FDG-PET resulted in major management changes in 58 (48%), minor changes in four (3%) and no change in 54 (45%). It can be concluded that FDG-PET has a significant impact on the management of patients with suspected recurrence of colorectal cancer. FDG-PET detection of recurrence frequently allows curative surgical intervention. The early identification of distant metastases may also facilitate the implementation of systemic treatment.

The role of positron emission tomography in gastrointestinal imaging

Although the use of PET in studies of the gastrointestinal tract is still relatively new, its value is clear. The future will provide a better definition of the indications for PET, refinement of the technology, and its relative value compared with other modalities such as peptide and antibody imaging, CT, MR imaging, and US.

Resection and local therapy for liver metastases

In 30-50% of patients the liver is a preferred site of distant disease for many malignant tumours. Due to the high incidence, most of the available data relate to metastases arising from colorectal primaries. Surgical resection is at present the only treatment offering potential cure. The achievable 5-year survival rate is 30%. However, only 10-15% of patients with colorectal liver metastases can undergo potentially curative liver resection. Therefore, accurate staging is an important prerequisite in selecting patients who would benefit from surgery. Recurrence of hepatic metastases after potentially curative resection occurs in up to 60% of the cases. Results demonstrate that re-resection of liver metastases can provide long-term survival rates in a carefully selected group of patients without extrahepatic disease. Because of the high rate of recurrences following an apparently curative resection several authors investigated the use of adjuvant chemotherapy (systemic, intraportal, and hepatic arterial infusion). Until recently none had shown effectiveness. Pre-operative chemotherapy seems to be a promising approach in patients with liver metastases initially considered unsuitable for radical surgery. Recently, neoadjuvant chemotherapy has been proposed as an alternative approach to conventional surgery as initial management with the aim of improving the results in resectable liver metastases. Interventional strategies (ethanol injection, cryosurgery, laser-induced thermotherapy, radio-frequency ablation) and combined modalities (surgical/interventional) are additive methods which may help to improve treatment results in the future.