Detection of hepatic metastases from cancers of the gastrointestinal tract by using noninvasive imaging methods (US, CT, MR imaging, PET): a meta-analysis

Liver metastases in cancer: detection with contrast-enhanced ultrasonography

In patients with known or suspected malignancy, ultrasonography (US) is often the first choice for liver imaging because of its widespread availability and low cost. Compared with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity of conventional US for detecting hepatic metastases is relatively poor. The advent of microbubble contrast agents changed this situation. Sensitivity and specificity increased substantially with the use of these contrast agents and contrast-specific imaging modes in recent years. Currently, numerous US imaging methods exist, based on Doppler techniques or harmonic imaging. They exploit the complex nonlinear behavior of microbubbles in a sound field to achieve marked augmentation of the US signal. Although microbubble contrast agents are essentially blood pool agents, some have a hepatosplenic specific late phase. Imaging during this late phase is particularly useful for improving the detection of malignant liver lesions and allows US to perform similarly to spiral CT as shown by recent studies. In addition, this late phase imaging is very helpful for lesion characterization. Low mechanical index imaging with the newer perfluor agents permits real-time imaging of the dynamic contrast behavior during the arterial, portal venous, and late phases and is particularly helpful for lesion characterization. The use of US for hemodynamic studies of the liver transit time may detect blood flow changes induced by micrometastases even before they become visible on imaging. In this field of functional imaging, further research is required to achieve conclusive results, which are not yet available.

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.

Liver cancer imaging: role of CT, MRI, US and PET

Liver imaging in patients with a history of known or suspected malignancy is important because the liver is a common site of metastatic spread, especially tumours from the colon, lung, pancreas and stomach, and in patients with chronic liver disease who are at risk for developing hepatocellular carcinoma. Since benign liver lesions are common, liver-imaging strategies should incorporate liver lesion detection and characterisation. Survey examination in patients with a known extra-hepatic malignancy to exclude the presence of hepatic and extra-hepatic involvement is normally undertaken with a contrast-enhanced computed tomography examination. When patients with hepatic metastases are being considered for metastasesectomy, they undergo a staging examination with contrast-enhanced magnetic resonance imaging (MRI) using tissue-specific contrast agents. Patients with chronic liver disease who are at risk for hepatocellular carcinoma undergo periodic liver screening for focal liver detection, usually with ultrasonography (US) with MRI being used when US is equivocal. Finally, contrast-enhanced MRI with extra-cellular gadolinium chelates is preferred for characterisation of indeterminate hepatic masses with liver biopsy used when tissue diagnosis is needed.

The value of routine serum carcino-embryonic antigen measurement and computed tomography in the surveillance of patients after adjuvant chemotherapy for colorectal cancer

PURPOSE

This analysis aims to evaluate routine carcino-embryonic antigen (CEA) and computed tomography (CT) of thorax, abdomen, and pelvis as part of protocol-specified follow-up policy for colorectal cancer (CRC).

PATIENTS AND METHODS

Patients with resected stage II and III CRC were randomly assigned to bolus fluorouracil/leucovorin or protracted venous infusion fluorouracil. Following completion of chemotherapy, patients were seen in clinic at regular intervals for 5 years. CEA was measured at each clinic visit, and CT of thorax, abdomen, and pelvis was performed at 12 and 24 months after commencement of chemotherapy.

RESULTS

Between 1993 and 1999, 530 patients were recruited. The median follow-up was 5.6 years. Disease relapses were observed in 154 patients. Relapses were detected by symptoms (n = 65), CEA (n = 45), CT (n = 49), and others (n = 9). Fourteen patients, whose relapses were detected by CT, had a concomitant elevation of CEA and were included in both groups. The CT-detected group had a better survival compared with the symptomatic group from the time of relapse (P =.0046). Thirty-three patients (21%) proceeded to potentially curative surgery for relapse and enjoyed a better survival than those who did not (P <.00001). For patients who underwent hepatic or pulmonary metastatic resection, 13 (26.5%) were in the CT group, eight (17.8%) in the CEA group, and only two (3.1%) in the symptomatic group (CT v symptomatic, P <.001; CEA v symptomatic, P =.015).

CONCLUSION

Surveillance CT and CEA are valuable components of postoperative follow-up in stage II and III colorectal cancer.

What is evidence-based medicine?1

RATIONALE AND OBJECTIVES

In this review article, we present the definition and useful concepts of evidence-based medicine (EBM). The principles of EBM are provided and major steps of practicing EBM are described.

MATERIALS AND METHODS

We emphasize the importance of the Cochrane Collaboration (see http://www.cochrane.org), which initiated the research and practice in this area. Because it can be difficult to systematically access and review individual research studies, it is often useful to focus on a critical overview of clinical trials by conducting a meta-analysis.

RESULTS

Useful literature and resources related to meta-analysis are provided.

CONCLUSION

Statistical methods for evaluating radiologic diagnostic performances derived from meta-analysis are summarized, with a special focus on summary outcomes measures.

Detection of occult liver metastases during EUS for staging of malignancies

BACKGROUND

EUS is commonly used in the staging of GI, thoracic, and other malignancies. Studies suggest EUS can detect occult liver metastases, but the frequency with which this occurs is unknown.

METHODS

Records were reviewed for all patients seen during a 3-year period who underwent EUS of the upper-GI tract for staging of known or suspected malignancy. Patients were included if there was histopathologic evidence of malignancy, they had undergone noninvasive liver imaging within 6 weeks of EUS, and liver surveillance was specifically mentioned in the report of the EUS procedure.

RESULTS

A total of 222 patients were included. Liver lesions were seen in 27 patients, 17 of whom had an abnormal noninvasive liver imaging test. EUS-guided FNA of the liver was performed in 21 patients and was diagnostic of malignancy in 15 (6.8%), 5 of whom (2.3%) had normal noninvasive imaging. In 6 patients, the EUS-guided FNA result was benign. EUS missed liver lesions in 4 patients known to have abnormalities by other imaging modalities.

CONCLUSIONS

EUS can detect occult liver metastases in patients in whom noninvasive hepatic imaging studies are normal, although the frequency at which such lesions are detected is low. Liver surveillance during EUS is worthwhile for patients in whom there is another indication for the procedure; but, at present, EUS should not replace traditional imaging modalities.

FGD-PET in the follow-up of recurrent colorectal cancer

OBJECTIVE

The current methods of detection of recurrent colorectal cancer after surgical treatment are inaccurate using conventional imaging. This study set out to detect early recurrence by means of PET in patients treated surgically for colorectal cancer by curative resection.

METHODS

Thirty-one disease-free patients were recruited and underwent FDG-PET. The results were verified by clinical, surgical and radiological follow up and/or biopsy to evaluate the accuracy for detecting recurrence.

RESULTS

PET detected 6 sites of increased activity in 5 patients. Three of these underwent surgery. One was false positive with no evident tumour and two underwent an hepatic resection with removal of a homental metastasis. The sensitivity was 100% and specificity 83.3%. Clinical management was altered in two cases (6.4%).

CONCLUSIONS

This study demonstrates that PET is more accurate than conventional imaging for the evaluation of recurrence in colorectal cancer patients. FDG-PET should be considered in the follow-up of patients after treatment for colorectal cancer in addition to other imaging methods.

Applications of positron emission tomography/computed tomography image fusion in clinical positron emission tomography-clinical use, interpretation methods, diagnostic improvements

Positron emission tomography (PET)/computed tomography (CT) scanners with combined dedicated high performance PET and CT scanners have been introduced recently in PET imaging. Oncological imaging with fluorodeoxyglucose (FDG) is currently the dominant application of PET. The addition of CT to PET offers many advantages, including obtaining a fast and relatively low-noise transmission scan, shortening the duration of the examination, adding precise anatomical information to FDG imaging, and providing additional diagnostic information. However, the use of CT for attenuation correction can lead to some artifacts that need to be considered when interpreting a PET/CT study: quantitative measurements may be altered, high density IV and oral and metallic objects may produce artifacts, and the registration of PET and CT may occasionally be suboptimal. Areas where using PET/CT offers particular potential advantages include the head and neck region, abdomen, and pelvis. Even in the thorax, PET/CT offers some advantages. Although clinical data evaluating the added value of PET/CT over PET are presently limited, preliminary results are very encouraging. More studies are warranted to clearly define the clinical impact of PET/CT over PET; however, it is clear this dedicated fusion technology will be very important for patient imaging in the coming years.

PET scan imaging in oncology

With the emergence of positron emission tomography (PET) from research laboratories into routine clinical use, it is important to redefine the most appropriate use of each imaging technique. The aim of this review article is to show the potential of PET in oncology. We discuss the most promising indications and the perspectives for the future. We will also point out the shortcomings and the important questions to be answered before fully considering PET as a necessary tool in the day-to-day practice of oncology. Although many studies have documented the high accuracy of 18F-FDG PET for the detection and staging of malignant tumours and for the monitoring of therapy results in these patients, it is very important to assess the impact of the technique on patient outcome and to show cost-effectiveness from the societal viewpoint.

Overview of preoperative and postoperative therapy for colorectal cancer: the European and United States perspectives

Surgery is the primary modality for cure in patients with localized colorectal cancer. However, despite potential curative surgery, the risk of recurrence is high. In colon cancer, the role of adjuvant chemotherapy with 5-fluorouracil (5-FU) and leucovorin (LV) is now established in stage III disease. The benefit of adjuvant treatment in stage II disease is likely to be small, and studies performed thus far have been generally underpowered to detect what might be a clinically significant effect on survival. Whereas bolus scheduling of 5-FU and LV is favored in North America, infusion of 5-FU/LV is preferred in Europe. Indeed, infused 5-FU/LV may be a safer partner with new drugs such as oxaliplatin and irinotecan. Oral fluoropyrimidines are attractive agents that might one day replace parenteral 5-FU. In rectal cancer, postoperative combined chemoradiation was recommended as standard practice in stages II and III disease. Despite a lack of randomized data demonstrating clinical benefit, preoperative chemoradiation has been increasingly used in patients with T3 disease in North America. However, preoperative radiation therapy is more frequently used in Europe. There are discrepancies in pathologic reporting of circumferential resection margin involvement and lymph node status between the United States and Europe. Standardized reporting with improved preoperative imaging would allow patients with truly early-stage disease to undergo more conservative management and be spared the morbidity and mortality of unnecessary adjuvant or neoadjuvant treatment.