REVIEW
Current Status of Imaging and Emerging Techniques to Evaluate Liver Metastases From Colorectal Carcinoma Dushyant V. Sahani, MD,∗ Mohammad Ali Bajwa, MD,∗ Yasir Andrabi, MD, MPH,∗ Surabhi Bajpai, MD,∗ and James C. Cusack, MD† Colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. Liver is a common site of tumor spread and in approximately 30% of the cases; synchronous liver disease is present at the time of diagnosis. Early detection of liver metastases is crucial to appropriately select patients who may benefit from hepatic resection among those needing chemotherapy, to improve 5-year survival. Advances in imaging techniques have contributed greatly to the management of these patients. Multidetector computed tomography is the most useful test for initial staging and in posttreatment surveillance settings. Magnetic resonance imaging is considered superior to multidetector computed tomography and positron emission tomography for the detection and characterization of small lesions and for liver evaluation in the presence of background fatty liver changes. Positron emission tomography–computed tomography has a problem-solving role in the detection of distant metastasis and in posttreatment evaluation. The advanced imaging methods also serve a role in selecting appropriate patients for radiologically targeted therapies and in monitoring response to conventional and novel therapies. Keywords: colorectal cancer, imaging, liver metastases, treatment options, treatment response monitoring (Ann Surg 2014;259:861–872)
C
olorectal cancer (CRC) is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society’s most recent estimates in the United States for 2011 are 141,210 new cases and 49,380 deaths.1 Liver is a common site of tumor spread and in approximately 30% of the cases, synchronous liver disease is present at the time of diagnosis. Even during chemotherapy almost 14.5% patients develop liver metastases.2,3 Early detection of liver metastases is crucial to appropriately select patients who may benefit from hepatic resection from those needing chemotherapy, to improve 5-year survival.4 Imaging plays an integral role in planning various treatments and monitoring the response. A variety of imaging techniques, including ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) scan, PET-CT are being currently used in the management of CRC. By virtue of its fast speed, higher resolution and availability, multidetector computed tomography (MDCT) is considered the imaging modality of choice for the initial evaluation of suspected or known liver metastases, whereas liver MRI is best utilized for problem-solving
From the ∗ Department of Radiology, Division of Abdominal Imaging and Intervention, and; and †Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA. Disclosure: The authors declare no conflicts of interest. Reprints: Dushyant V. Sahani, MD, Department of Radiology, Division of Abdominal Imaging and Intervention, Massachusetts General Hospital, Harvard Medical School, White 270, 55 Fruit St, Boston, MA 02114. E-mail: [email protected]. C 2014 by Lippincott Williams & Wilkins Copyright ISSN: 0003-4932/14/25905-0861 DOI: 10.1097/SLA.0000000000000525
Annals of Surgery r Volume 259, Number 5, May 2014
situations in the detection and characterization of small lesions. 18 F-Fluorodeoxyglucose (18 F-FDG)-PET-CT assumes an important role in the detection of extrahepatic metastases and is also a sensitive test for liver metastases detection.5–7
ROLE OF IMAGING IN THE DETECTION OF COLORECTAL LIVER METASTASES Although transabdominal US is the least expensive and most readily available modality to screen the liver, it has relatively low sensitivity for the detection of metastatic lesions.5 Studies have shown that it fails to recognize over 50% of liver metastases. High operator dependence and patient’s body habitus are limitations inherent to US. Liver steatosis, a common occurrence in patients receiving chemotherapy, is also an impediment to US performance for lesion detection. Inadequate lesion characterization and detection of extrahepatic disease are other challenges with US. However, US is useful in screening for biliary obstruction from neoplastic causes or other causes in patients presenting with jaundice. Table 1 summarizes advantages and limitations of various imaging modalities in evaluating liver metastases. In contrast, intraoperative ultrasonography (IOUS) provides high-resolution imaging of the liver and its vascular structures and is frequently used for intraoperative decision making. Specifically, localization of deep-seated, nonpalpable lesions can be facilitated by IOUS. Moreover, by mapping the major hepatic veins and determining the relationship of the liver lesions to the adjacent vascular structures, IOUS provides real-time guidance for the surgical resection plane. Although the reported sensitivity of IOUS ranges from 85% to 95%, its independent sensitivity for liver lesion detection is not well known as the operator usually has a prior knowledge of liver tumors detected on preoperative imaging studies. The performance of IOUS is also dependent on the operator’s experience, lesion size, location, and echogenicity. Although IOUS may increase the duration of surgery by a few minutes, it plays a significant role in the surgical management of liver metastases. Earlier studies showed that findings on IOUS altered the planned surgical approach in 44% to 83% of patients; however the routine use of advanced imaging tests such as MRI and PET-CT before surgery has significantly decreased the yield of IOUS for the intraoperative detection of new lesions that would alter the surgical plan.9–12 There has been increasing interest with the use microbubble contrast media (CM) to overcome some of the limitations of US for the detection of liver metastases using either the transabominal or intraoperative approach. In few clinical trials, microbubble contrastenhanced (CE)-US has shown a performance comparable to CT and CE-MRI in liver lesion detection and characterization.13–18 However, these microbubbles agents have not yet received the regulatory approval for the clinical use in North America. MDCT has emerged as the modality of choice for staging of CRC and screening for liver metastases. Rapid technological advancements in CT and improved resolution and scanning speed have enabled MDCT to attain a higher sensitivity and specificity in the detection of liver metastases.19–22 Liver metastases for CRC (mCRC) www.annalsofsurgery.com | 861
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Annals of Surgery r Volume 259, Number 5, May 2014
Sahani et al
TABLE 1. Advantages and Limitations of Various Imaging Modalities in Evaluating Liver Metastases Modality
Advantages
US
Low cost Availability
IOUS
Localization of deep-seated lesion Mapping vasculature Real-time guidance for surgical plane Guiding RFA Availability Relatively low cost High sensitivity and specificity Extrahepatic spread evaluation Vascular mapping Liver volume estimation Planning targeted therapies Therapy monitoring
MDCT
MRI
PET
Increased sensitivity and specificity for Detection of small lesions(
Current Status of Imaging and Emerging Techniques to Evaluate Liver Metastases From Colorectal Carcinoma Dushyant V. Sahani, MD,∗ Mohammad Ali Bajwa, MD,∗ Yasir Andrabi, MD, MPH,∗ Surabhi Bajpai, MD,∗ and James C. Cusack, MD† Colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. Liver is a common site of tumor spread and in approximately 30% of the cases; synchronous liver disease is present at the time of diagnosis. Early detection of liver metastases is crucial to appropriately select patients who may benefit from hepatic resection among those needing chemotherapy, to improve 5-year survival. Advances in imaging techniques have contributed greatly to the management of these patients. Multidetector computed tomography is the most useful test for initial staging and in posttreatment surveillance settings. Magnetic resonance imaging is considered superior to multidetector computed tomography and positron emission tomography for the detection and characterization of small lesions and for liver evaluation in the presence of background fatty liver changes. Positron emission tomography–computed tomography has a problem-solving role in the detection of distant metastasis and in posttreatment evaluation. The advanced imaging methods also serve a role in selecting appropriate patients for radiologically targeted therapies and in monitoring response to conventional and novel therapies. Keywords: colorectal cancer, imaging, liver metastases, treatment options, treatment response monitoring (Ann Surg 2014;259:861–872)
C
olorectal cancer (CRC) is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society’s most recent estimates in the United States for 2011 are 141,210 new cases and 49,380 deaths.1 Liver is a common site of tumor spread and in approximately 30% of the cases, synchronous liver disease is present at the time of diagnosis. Even during chemotherapy almost 14.5% patients develop liver metastases.2,3 Early detection of liver metastases is crucial to appropriately select patients who may benefit from hepatic resection from those needing chemotherapy, to improve 5-year survival.4 Imaging plays an integral role in planning various treatments and monitoring the response. A variety of imaging techniques, including ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) scan, PET-CT are being currently used in the management of CRC. By virtue of its fast speed, higher resolution and availability, multidetector computed tomography (MDCT) is considered the imaging modality of choice for the initial evaluation of suspected or known liver metastases, whereas liver MRI is best utilized for problem-solving
From the ∗ Department of Radiology, Division of Abdominal Imaging and Intervention, and; and †Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA. Disclosure: The authors declare no conflicts of interest. Reprints: Dushyant V. Sahani, MD, Department of Radiology, Division of Abdominal Imaging and Intervention, Massachusetts General Hospital, Harvard Medical School, White 270, 55 Fruit St, Boston, MA 02114. E-mail: [email protected]. C 2014 by Lippincott Williams & Wilkins Copyright ISSN: 0003-4932/14/25905-0861 DOI: 10.1097/SLA.0000000000000525
Annals of Surgery r Volume 259, Number 5, May 2014
situations in the detection and characterization of small lesions. 18 F-Fluorodeoxyglucose (18 F-FDG)-PET-CT assumes an important role in the detection of extrahepatic metastases and is also a sensitive test for liver metastases detection.5–7
ROLE OF IMAGING IN THE DETECTION OF COLORECTAL LIVER METASTASES Although transabdominal US is the least expensive and most readily available modality to screen the liver, it has relatively low sensitivity for the detection of metastatic lesions.5 Studies have shown that it fails to recognize over 50% of liver metastases. High operator dependence and patient’s body habitus are limitations inherent to US. Liver steatosis, a common occurrence in patients receiving chemotherapy, is also an impediment to US performance for lesion detection. Inadequate lesion characterization and detection of extrahepatic disease are other challenges with US. However, US is useful in screening for biliary obstruction from neoplastic causes or other causes in patients presenting with jaundice. Table 1 summarizes advantages and limitations of various imaging modalities in evaluating liver metastases. In contrast, intraoperative ultrasonography (IOUS) provides high-resolution imaging of the liver and its vascular structures and is frequently used for intraoperative decision making. Specifically, localization of deep-seated, nonpalpable lesions can be facilitated by IOUS. Moreover, by mapping the major hepatic veins and determining the relationship of the liver lesions to the adjacent vascular structures, IOUS provides real-time guidance for the surgical resection plane. Although the reported sensitivity of IOUS ranges from 85% to 95%, its independent sensitivity for liver lesion detection is not well known as the operator usually has a prior knowledge of liver tumors detected on preoperative imaging studies. The performance of IOUS is also dependent on the operator’s experience, lesion size, location, and echogenicity. Although IOUS may increase the duration of surgery by a few minutes, it plays a significant role in the surgical management of liver metastases. Earlier studies showed that findings on IOUS altered the planned surgical approach in 44% to 83% of patients; however the routine use of advanced imaging tests such as MRI and PET-CT before surgery has significantly decreased the yield of IOUS for the intraoperative detection of new lesions that would alter the surgical plan.9–12 There has been increasing interest with the use microbubble contrast media (CM) to overcome some of the limitations of US for the detection of liver metastases using either the transabominal or intraoperative approach. In few clinical trials, microbubble contrastenhanced (CE)-US has shown a performance comparable to CT and CE-MRI in liver lesion detection and characterization.13–18 However, these microbubbles agents have not yet received the regulatory approval for the clinical use in North America. MDCT has emerged as the modality of choice for staging of CRC and screening for liver metastases. Rapid technological advancements in CT and improved resolution and scanning speed have enabled MDCT to attain a higher sensitivity and specificity in the detection of liver metastases.19–22 Liver metastases for CRC (mCRC) www.annalsofsurgery.com | 861
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Annals of Surgery r Volume 259, Number 5, May 2014
Sahani et al
TABLE 1. Advantages and Limitations of Various Imaging Modalities in Evaluating Liver Metastases Modality
Advantages
US
Low cost Availability
IOUS
Localization of deep-seated lesion Mapping vasculature Real-time guidance for surgical plane Guiding RFA Availability Relatively low cost High sensitivity and specificity Extrahepatic spread evaluation Vascular mapping Liver volume estimation Planning targeted therapies Therapy monitoring
MDCT
MRI
PET
Increased sensitivity and specificity for Detection of small lesions(
