Hepatic metastases: basic principles and implications for radiologists

Liver involvement in patients with solid tumors of nonhepatic origin

Metastatic disease represents the most common hepatic neoplasm in the Western world. The most common primary malignancies to spread to the liver are those that originate in the gastrointestinal tract. Of non-gastrointestinal malignancies, breast, lung, and melanoma malignancies are most likely to develop hepatic metastases. Some solid tumors, such as renal cell carcinoma, may cause liver-related abnormalities in the absence of hepatic metastases, presumably by way of cytokine-mediated mechanisms. Physical examination, laboratory testing, histologic evaluation, and various radiographic studies are useful in the detection and diagnosis of liver metastases. Multiple treatment modalities are available, including hepatic resection, hepatic arterial chemotherapy, systemic chemotherapy, chemoembolization, cryotherapy, ethanol injection, and radiofrequency ablation.

Cystic changes in hepatic metastases from gastrointestinal stromal tumors (GISTs) treated with Gleevec (imatinib mesylate)

OBJECTIVE

The purpose of this article is to illustrate the CT findings in patients with hepatic metastases from a gastrointestinal stromal tumor who were treated with STI-571.

CONCLUSION

Hepatic metastases from gastrointestinal stromal tumors that respond to treatment with STI-571 can appear as near-cystic components with well-defined borders on contrast-enhanced CT. Most metastases became smaller. These metastases resemble simple cysts, but density measurements may differentiate them from one another.

Computed tomography and magnetic resonance imaging of hepatic metastases

The detection and characterization of liver metastases is well performed with either computed tomography or magnetic resonance imaging. The administration of intravenous contrast is essential for almost all indications, with multiphasic imaging aiding in lesion characterization and detection. The use of multidetected CT (MDCT) provides the ability for optimized vascular and multiplanar imaging, but has also resulted in increased examination complexity. Tissue-specific MR contrast agents can yield the highest rate of lesion detection and thus may be useful in presurgical planning.

Positron emission tomography (PET) and other nuclear medicine modalities in staging gastrointestinal cancer

Gastrointestinal (GI) cancers account for the second highest number of new tumor cases and deaths per year in the United States and Western Europe. The most frequently involved sites are, in descending order, the colorectum, stomach, pancreas, liver, bile duct, and esophagus. The most common tumor type is adenocarcinoma. Among the epithelial cancers, great attention has recently been given to the tumors of neuroendocrine origin. These concepts are relevant because nuclear medicine imaging is based on visualization by means of a particular uptake of radiolabelled tracers in cancer cells that concentrate the radioactive signal. This signal is detected and reconstructed in planar or tomographic images. Different radiopharmaceuticals have been proposed for diagnostic application in oncology (such as radiolabelled monoclonal antibodies (MAbs), receptor tracers, and positron-emitting radiopharmaceuticals), and they are currently used as tracers for tumor detection with different modalities and techniques. Most of these techniques demonstrate their clinical usefulness in the diagnosis of GI cancer. This work is not intended to be a comprehensive review of all the extensive experience and possibilities of nuclear medicine for the diagnosis of GI tumors; rather, it aims to summarize the current status of the most important approaches and their main indications in staging GI cancers.

Early changes in liver perfusion caused by occult metastases in rats: detection with quantitative CT

PURPOSE

To determine whether computed tomography (CT) can depict liver hemodynamic changes caused by occult hepatic micrometastases in rat.

MATERIALS AND METHODS

Liver micrometastases (mean diameter, 500 micrometer +/- 300) were produced in seven BD IX rats by injecting 10(7) DHDK12 PROb colorectal carcinoma cells into the spleen. Macrometastases (mean diameter, 7 mm +/- 3) were produced in four other rats. Five normal rats were studied as controls. CT images were obtained every 300 msec for 30 seconds during the injection of 1 mL per kilogram of body weight of contrast medium. The time-attenuation curves of the aorta, portal vein, and liver were used to calculate liver perfusion with a deconvolution model designed for the dual blood supply.

RESULTS

Micrometastases in an apparently normal liver caused a 34% decrease in portal blood flow and a 25% increase in the mean transit time for the blood to pass through the liver. These findings suggest increased resistance in the sinusoidal capillaries. Similar but greater changes were found in the macrometastases.

CONCLUSION

Occult liver micrometastases in rats generate changes in liver perfusion that can be detected with CT.

Hepatic metastases from colorectal cancer: preoperative detection and assessment of resectability with helical CT

PURPOSE

To prospectively evaluate helical computed tomography (CT) in the preoperative detection of hepatic metastases and assessment of resectability with surgical, intraoperative ultrasonographic (US), and histopathologic correlation.

MATERIALS AND METHODS

Between October 1995 and December 1998, preoperative staging with helical CT (5-mm collimation; reconstruction interval, 5 mm) was performed in 157 patients with hepatic metastases. Iodinated contrast material was injected intravenously (160-170 mL; rate, 2.5-3.0 mL/sec); acquisition began at 60-70 seconds. Four radiologists prospectively assessed the metastatic involvement of the liver by indicating the number and location of the lesions; resection was indicated in 113 patients (119 instances). Helical CT findings were correlated with pathologic and surgical findings on a lesion-by-lesion basis.

RESULTS

Intraoperative US, palpation, and histopathologic examination revealed 290 liver metastases; helical CT correctly depicted 247. Helical CT results were the following: overall detection rate, 85.1% (95% CI: 80.8%, 89.3%); positive predictive value, 96.1% (95% CI: 92.9%, 98.1%); and false-positive rate, 3.9% (10 of 257 findings; 95% CI: 1.9%, 7.1%). False-positive findings were related to hemangioendothelioma, hemangioma, hepatic peliosis, biliary adenoma, centrilobar hemorrhage, biliary hamartoma, periportal fibrosis, and normal liver parenchyma. Curative resection was performed in 112 instances with a resectability rate of 94.1%. Four-year patient survival rate was 58.6%.

CONCLUSION

Helical CT is a noninvasive, reliable, and accurate technique for imaging the liver and should be considered as the standard preoperative work-up of hepatic metastases from colorectal cancer.

Evaluation of the accuracy of gadobenate dimeglumine-enhanced MR imaging in the detection and characterization of focal liver lesions

OBJECTIVE

We evaluated the extent to which hepatic lesion characterization and detection is improved by using gadobenate dimeglumine for enhancement of MR images.

MATERIALS AND METHODS

Eighty-six patients were imaged before gadobenate dimeglumine administration, immediately after the 2 mL/sec bolus administration of a 0.05 mmol/kg dose (dynamic imaging), and at 60-120 min after the IV infusion at 10 mL/min of a further 0.05 nmol/kg dose (delayed imaging). The accuracy for lesion characterization was assessed for a total of 107 lesions. Sensitivity for lesion detection was assessed for a total of 149 lesions detected on either intra-operative sonography, iodized oil CT, CT during arterial portography, or follow-up contrast-enhanced CT as the gold standard.

RESULTS

The accuracy in differentiating benign from malignant liver lesions increased from 75% and 82% (the findings of two observers) on unenhanced images alone, to 89% and 80% on dynamic images alone (p<0.001, p = 0.8), and to 90.7% when combining the unenhanced and dynamic image sets (p<0.001, p = 0.023). Delayed images did not further improve accuracy (90% and 91%; p = 0.002, p< 0.05). A similar trend was apparent in terms of accuracy for specific diagnosis: values ranged from 49% and 62% on unenhanced images alone, to 76% and 70% on combined unenhanced and dynamic images (p<0.001, p = 0.06), and to 75% and 70% on inclusion of delayed images (p<0.001, p = 0.12). The sensitivity for lesion detection increased from 77% and 81% on unenhanced images alone, to 87% and 85% on combined unenhanced and dynamic images (p = 0.001, p = 0.267), and to 92% and 89% when all images were considered (p<0.001, p = 0.01).

CONCLUSION

Contrast-enhanced dynamic MR imaging with gadobenate dimeglumine significantly increases sensitivity and accuracy over unenhanced imaging for the characterization of focal hepatic lesions, and delayed MR imaging contributes to the improved detection of lesions.

Hepatic metastases from breast carcinoma: comparison of noncontrast, arterial-dominant, and portal-dominant phase spiral CT

PURPOSE

The purpose of this work was to determine the relative value of noncontrast (NC), arterial-dominant (AD), and portal-dominant (PD) phase images in spiral CT of the liver for breast cancer metastases.

METHOD

Forty-four spiral CT scans in 18 patients with hepatic metastases from breast cancer were retrospectively reviewed by three radiologists. Subjective evaluations of overall lesion conspicuity and margination were graded on a 5 point scale for NC, AD, and PD phase images, and the three phases were also ranked for demonstration of overall tumor volume. Those scans with hypervascular lesions were separately analyzed, resulting in three groups (all, hypervascular, hypovascular).

RESULTS

For lesion conspicuity and margination for the entire study group, AD phase images showed the lowest grades (1.97 and 1.83), whereas the PD phase showed the highest grade (3.34 and 3.14; p < 0.0001) followed by NC (2.36 and 2.42; p < 0.0001). For the hypervascular subgroup, the AD phase also showed the lowest grades (2.39 and 2.24). In no case did the AD phase show more lesions than the combination of NC and PD phases. For depiction of overall tumor volume, the AD phase had the lowest ranking (2.51) compared with the NC and PD phases (1.71 and 1.78; p < 0.001). For the hypervascular subgroup, the AD phase had the lowest ranking (2.33) compared with the NC and PD phases (1.39 and 2.27; p < 0.0001).

CONCLUSION

The AD phase is not required for lesion detection in spiral CT for hepatic metastases from breast carcinoma. The NC phase depicts the maximal tumor volume.

The changing role of radiology in imaging liver tumors: an overview

The surgical and the radiological advances in liver tumors in last two decades have made some malignant tumors operable which were considered inoperable and have completely changed the expectations from radiology. However, accurate staging, that is performed by imaging modalities, has critical importance in the selection of patients who can benefit from resection. Radiologists and referring physicians, therefore, should be aware of the current concepts in imaging liver tumors. This report updates both the changing role of radiology in hepatic neoplasms and the appropriate use of radiological modalities in liver tumors.

DNA ploidy of liver biopsies from patients with liver cirrhosis and hepatocellular carcinoma: a flow cytometric analysis

Flow cytometric DNA analysis was used to assess cellular kinetics of needle liver biopsies from patients with liver cirrhosis and hepatocellular carcinoma (HCC). An abnormal DNA content was shown in 44.5% of liver cirrhosis cases and in 78.6% of tumor sites. The number of proliferating cells (S + G2M%) was significantly increased in cirrhotic liver (P < 0.05). Dysplasia was found in 66% of cirrhotic specimens. All negative dysplasia specimens showed a diploid pattern while 69% of positive dysplastic specimens were aneuploid (P < 0.001). In conclusion, cell proliferation, aneuploidy and liver cell dysplasia are important indicators in liver cirrhosis for the development of HCC.

Lung cancer staging and management: comparison of contrast-enhanced and nonenhanced helical CT of the thorax

PURPOSE

To determine whether contrast material-enhanced helical computed tomography (CT) of the thorax and upper abdomen changes the tumor stage and management compared with nonenhanced helical CT in patients with newly diagnosed lung cancer.

MATERIALS AND METHODS

During 15 months, any patient in whom lung cancer was strongly suspected or newly diagnosed and who was scheduled for thoracic CT was considered eligible for the study. All patients underwent nonenhanced thoracic helical CT from the lung apices through the adrenal glands and then contrast-enhanced thoracic helical CT from the lung apices through the entire liver. Each study was read independently, and the thoracic radiologic stage was determined. Tissue sampling was performed and the final pathologic stage assigned.

RESULTS

Ninety-six patients had a final pathologic diagnosis of lung cancer. There was agreement in stage between the nonenhanced and contrast-enhanced examinations in 92 of the 96 patients. In three patients, the tumor stage at nonehanced CT increased at contrast-enhanced CT, from IA to IIA (n = 1), IIB to IV (n = 1), and IIIB to IV (n = 1). In one patient, the tumor stage decreased from IIIB to IIB. There was no substantial change in management of any patient.

CONCLUSION

The results suggest that contrast-enhanced thoracic CT through the liver for staging lung cancer rarely changes the tumor stage determined with nonenhanced CT through the adrenal glands and does not substantially influence management decisions.

Improved imaging of liver metastases with stimulated acoustic emission in the late phase of enhancement with the US contrast agent SH U 508A: early experience

PURPOSE

To see whether stimulated acoustic emission (SAE) in the liver parenchyma in the late phase of enhancement with SH U 508A increases the conspicuity of occult metastases at ultrasonography (US).

MATERIALS AND METHODS

Eighteen patients with known hypo- or hypervascular hepatic metastases underwent US after SH U 508A administration, after a delay of at least 5 minutes, to ensure decay of blood pool enhancement. In 16 patients with visible metastases, conspicuity was compared on registered SAE and gray-scale scans by two blinded readers and by using computerized analysis of relative gray-scale and color Doppler conspicuity scores inside and outside the lesion. In nine patients, areas suspected of being involved but without definite gray-scale masses were imaged in the same way. Paired sections were analyzed by two blinded readers looking for parenchymal color defects without corresponding gray-scale masses; nine control images from three healthy volunteers were also included.

RESULTS

Intense, transient parenchymal SAE was seen in all subjects. All metastases appeared as areas of reduced or absent signal. The conspicuity score was 80% for SAE versus 9% for gray-scale US (P < .001, Wilcoxon signed rank test). SAE-specific defects were seen in all patients but in none of the volunteers. Metastases seen on SAE but undetectable on gray-scale images were proved in three patients.

CONCLUSION

SAE with SH U 508A improves the conspicuity of metastases. SAE-specific defects may reveal isoechoic or subtle metastases.

Clinical evaluation of whole-body 18F-fluorodeoxyglucose positron emission tomography in the detection of liver metastases

BACKGROUND

Assessment of metastatic involvement of the liver remains a diagnostic challenge. The objective of this study was to evaluate the potential role of FDG PET in the detection of liver metastases.

PATIENTS AND METHODS

Sixty-four patients with malignancy and possible liver involvement were included. Liver metastases were present in 31 cases, demonstrated by histopathological analysis in 15 cases and by follow-up in 16 cases. The negative cases were confirmed by pathology in four cases, peroperative ultrasonography in 12 cases, and follow-up in 17 cases. Whole-body FDG PET was compared to CT (n = 53) and US (n = 43).

RESULTS

PET demonstrated a 97% sensitivity, an 88% specificity and a 92% accuracy, compared to 93%, 75% and 85%, respectively, for CT (P = NS). Concordant results were obtained in 44 of 64 patients (69%: 19 TP. 25 TN). PET provided new and accurate information in 15 of 64 patients (23.4%). PET demonstrated liver metastases in 11 patients in whom conventional methods yielded negative (two cases) or doubtful (nine cases) results. Four patients free of liver involvement were correctly staged with PET, while CT/US were equivocal. PET was erroneous in five of 64 cases (7.8%, four FP, one FN).

CONCLUSIONS

FDG PET allows an accurate screening of liver involvement in patients with malignancy. Combined with CT, it provides additional diagnostic information that could directly affect the management of these patients.

Hepatic metastases

Developments in ultrasound, CT scan, and MR imaging have increased our ability to detect and characterize focal liver lesions. Advances in the medical and surgical treatment of secondary liver tumors have continued to challenge these advances in radiology. A successful outcome depends on knowledge of the size and location of the tumor burden, and accurate radiologic assessment is crucial to identify those subgroups who may benefit from surgery and to prevent unnecessary radical surgery in those likely to gain only a short-term benefit.

Hepatic imaging. An overview

Recent advances in ultrasound, CT scan, MR imaging, and scintigraphy permit characterization of a variety of focal and diffuse liver diseases. Accurate clinical information, however, is of vital importance in selecting the optimal imaging modality and interpreting the study accurately. Using a combination of radiologic findings and clinical information, a correct diagnosis may be achieved noninvasively.

Magnetic resonance imaging of focal and diffuse hepatic disease

MRI is a powerful tool in the detection and characterization of both focal and diffuse liver pathology. Because of superior soft tissue characterization, direct multi-planar capabilities and lack of ionizing radiation, current state of the art MRI is useful when contrast CT is relatively contraindicated or not definitive. This article reviews the MRI findings of the most common focal and diffuse liver diseases encountered in clinical practice. Reviews of current MR techniques and MR contrast agents used in liver imaging have been recently published. For this article, discussion of specific techniques and use of contrast is addressed for each pathological entity discussed.

MnDPDP as a negative hepatic contrast agent: evaluation of STIR imaging compared with T1-weighted SE and GE techniques

Our goal was to assess the utility of manganese dipyridoxyl diphosphate (MnDPDP) as a negative hepatic contrast agent in short inversion time IR MRI (STIR). Twenty patients with focal liver lesions (15 with metastatic disease, 5 with hemangiomas) underwent MRI (T1-weighted SE, breath-hold GE, and STIR sequences) before and after infusion of MnDPDP (5 mumol/kg). We then compared the results obtained with each sequence for hepatic parenchymal enhancement, lesion-to-liver contrast-to-noise ratio (C/N) measurements, and the number of focal liver lesions observed in pre- and postcontrast images. Hepatic enhancement values of 25.3 +/- 9.7 and 33.6 +/- 2.7% (mean +/- SEM) were obtained for the T1-weighted SE and GE sequences, respectively. The STIR sequence showed 78.9 +/- 2.1% negative enhancement (decrease of parenchymal signal intensity). Although a significant (p < 0.0001) C/N increase was seen after MnDPDP administration for all sequences, STIR showed the highest increase (149.0 +/- 25.5%) compared with T1-weighted SE (58.5 +/- 12.7%) and GE (83.3 +/- 7.2%) sequences. Similarly, more lesions for all sequences were detected, but again STIR showed the greatest postcontrast increase (29.0%). MnDPDP is an effective hepatic contrast agent. As both the negative hepatic enhancement and the increase in lesion-to-liver C/N were superior with the STIR sequence when compared with the positive enhancement and C/N values produced by the T1-weighted sequences, it should be considered for inclusion in the imaging protocol for patients with focal liver disease.

Oncological applications of positron emission tomography with fluorine-18 fluorodeoxyglucose

Positron emission tomography (PET) is now primarily used in oncological indication owing to the successful application of fluorine-18 fluorodeoxyglucose (FDG) in an increasing number of clinical indications at different stages of diagnosis, and for staging and follow-up. This review first considers the biological characteristics of FDG and then discusses methodological considerations regarding its use. Clinical indications are considered, and the results achieved in respect of various organs and tumour types are reviewed in depth. The review concludes with a brief consideration of the ways in which clinical PET might be improved.