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essentials.of.thoracic.imaging-1416027602.pdf Radiol Clin NPreface Essentials of Thoracic Imaging Caroline Chiles, MD Guest EditorDiagnostic radiology, like many other medical specialties, does not allow physicians to maintain competence solely on the basis of accumulating ex- perience, but requires a commitment to life– long learning. Keeping pace with new knowledge and new technology competes with clinical demands on a radiologist’s time. At the 2002 annual meeting in Chicago, the Radiological Society of North America initiated a series of continuing medical education lectures called bThe Essentials.Q Attendance and audience feedback surpassed all expectations. Sur- veys of radiologists attending bThe EssentialsQ lectures showed an equal mix of general radiologists, and radiologists who practice subspecialties outside the lecture topic. The participants were seeking prac- tical information that would impact their daily radiol- ogy work—applying new technologies to diseases that are encountered every day. My goal for this issue of Radiologic Clinics of North America is to condense the overwhelming0033-8389/05/$ – see front matter D 2005 Elsevier Inc. All rights doi:10.1016/j.rcl.2005.03.001amount of current literature in thoracic radiology to the application of new technologies to bread-and- butter cases. Thank you to my colleagues who have shared their expertise in the basics of thoracic imag- ing: lung cancer, metastatic disease, the solitary pul- monary nodule, pneumonia, cardiovascular disease, and high resolution CT. Thank you as well to Ron Zagoria, who included me in the initial Radiological Society of North America Essentials faculty, and to Barton Dudlick, who saw this project through from start to finish. Caroline Chiles, MD Division of Radiological Sciences Department of Radiology Wake Forest University School of Medicine Medical Center Boulevard Winston-Salem, NC 27157-1088, USA E-mail address: cchiles@wfubmc.eduAm 43 (2005) xireserved. radiologic.theclinics.com Radiol Clin N AmImaging of Non–Small Cell Lung Cancer Reginald F. Munden, MD, DMD*, John Bruzzi, MD Division of Diagnostic Imaging, Department of Radiology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USALung cancer is the most common type of cancer and the leading cause of cancer deaths in the United States for both men and women. It was estimated that 173,770 new cases and 160,440 deaths from lung cancer would occur in 2004 [1]. More Americans die of lung cancer than of colorectal, breast, and prostate cancers combined, which are the second through fourth leading causes of cancer mortality, respec- tively. Even though major efforts at improving sur- vival have occurred over the years, the overall 5-year survival of lung cancer remains dismal at 14% for all stages (clinical staging), 61% for stage IA, 38% for stage IB, 34% for stage IIA, 24% for stage IIB, 13% for stage IIIA, 5% for stage IIIB, and 1% for stage IV [2]. Once lung cancer has been established, the Inter- national System for Staging Lung Cancer is used to stage newly diagnosed non–small cell lung cancer (NSCLC). This system describes the extent of NSCLC in terms of the size, location, and extent of the primary tumor (T descriptor); the presence and location of lymph node involvement (N descriptor); and the presence or absence of distant metastatic disease (M descriptor) [2]. Radiologic evaluation is an important component of the clinical staging evaluation and can greatly influence whether the patient is treated with surgical resection, radiation therapy, chemotherapy, or a combination of these modalities [3]. In addition to staging, the radiologic evaluation of the patient undergoing treatment and subsequent follow-up is important to the clinician for0033-8389/05/$ – see front matter D 2005 Elsevier Inc. All rights doi:10.1016/j.rcl.2005.01.009 * Corresponding author. E-mail address: rmunden@mdanderson.org (R.F. Munden).assessing treatment effects and complications. This article discusses the imaging in patients with NSCLC and its use in caring for these patients.Importance of staging lung cancer Because surgical resection of lung cancer offers the best chance of cure, accurate staging is important to determine if patients are surgical candidates. In general, clinical stage I, II, and some stage IIIA pa- tients are considered to have disease that is resectable, whereas more extensive disease as in some patients with stage IIIA and most with stage IIIB and IV is treated with radiation therapy, chemotherapy, or a combination of both [4]. More than 60% of patients with lung cancer receive radiotherapy at some point in their disease, 17% of which is for palliation [5]. Patients with early stage disease (stage I–II) who are not surgical candidates because of medical comor- bidities or who refuse surgery may undergo radio- therapy with curative intent [6]. Radiotherapy may also be used as preoperative concurrent chemo- radiotherapy in locally advanced lung cancer to ‘‘downstage’’ the patient to a lower stage and make them a candidate for surgical cure. Preliminary studies suggest this technique may have a role in treating NSCLC, but remains controversial [7]. For locally advanced and inoperable lung cancer, chemo- therapy is used in conjunction with radiation therapy to improve survival [8–10]. Chemotherapy alone is used in stage III and IV NSCLC patients who are not candidates for surgery or chemoradiation. Because the determination of disease extent is often based on clinical staging, imaging studies and the radiologist’s interpretation are very important43 (2005) 467 – 480reserved. radiologic.theclinics.com Fig. 1. A 60-year-old man with T2 non–small cell lung cancer. Axial image from a contrast-enhanced CT scan shows that the primary tumor is located centrally (arrow), causing distal postobstructive atelectasis. Note the difficulty of differentiating tumor from collapsed lung parenchyma. munden & bruzzi468aspects of the treatment plan decision between surgery, radiation therapy, chemotherapy, or a combi- nation of treatments. Common imaging modalities for staging lung cancer are chest radiographs, CT, MR imaging, positron-emission tomography (PET), and fused PET-CT. Although a common method of detecting lung cancer, chest radiographs are of lim- ited value in staging lung cancer. The most common radiologic examination in the lung cancer patient is chest CT [11] because of its ability to provide anatomic information regarding the primary tumor and evaluate the extent of intrathoracic and regional extrathoracic disease. Whole-body PET using fluorine- 18–fluorodeoxyglucose (18F-FDG) has become a very useful tool in staging lung cancer; fused PET– CT imaging is a newer technique that has further improved staging [3,12,13].Staging The radiologic evaluation of the primary tumor (T descriptor) should describe the size, location, mar- gins, and relationship to adjacent structures for the surgeon, radiation oncologist, or medical oncologist to determine an appropriate treatment plan. T1 tumors are technically the easiest to resect because they are smaller (< 3 cm) and are limited to the lung paren- chyma. T1 tumors are surrounded by lung paren- chyma but may reside near other structures that are important to note. As an example, tumors adjacent to pulmonary vessels may require a change in surgical technique or radiotherapy treatment plan. T2 tumors are larger (
3 cm), but should not be closer than 2 cm to the carina and may have asso- ciated atelectasis or pneumonitis that does not include the entire lobe (Fig. 1). As with T1 tumors, the ana- tomic relationship of the tumor to nearby structures may influence the treatment plan and should be reported. For instance, if the lobar bronchus or main bronchus is involved by tumor, a sleeve resection or pneumonectomy may be required [14]. Associated atelectasis is important because it may require an alteration in the radiotherapy treatment plan. T3 tumors can be any size; invade the chest wall, diaphragm, mediastinal pleura, parietal pericardium, or be within 2 cm of the carina; or have associated atelectasis or pneumonitis of the entire lobe. Appro- priate description of location is important because if the tumor is less than 2 cm from the carina, a carinal pneumonectomy needs to be performed [15]. The extent of chest wall invasion is also important to convey because more extensive surgical techniques or larger radiotherapy treatment plans are required.The sensitivity and specificity of CT in determining chest wall invasion is reported to vary from 38% to 87% and 40% to 90%, respectively [16]. Glazer et al [17] reported CT to have 87% sensitivity, 59% speci- ficity, and 68% accuracy for assessing chest wall invasion; however, local chest pain was more specific (94%) and accurate (85%). MR imaging sensitivity and specificity (63%–90% and 84%–86%, respec- tively) in diagnosing chest wall invasion are similar to those of CT [16,18,19]. Even though radiologic evaluation for chest wall invasion is somewhat limi- ted, at times definite invasion can be determined, and important to note for treatment planning. Likewise, if invasion is not definite, this uncertainty should also be noted. Invasion of the primary tumor into the medias- tinum is also important to assess. As in chest wall invasion, CT and MR imaging can be accurate (56%–89% and 50%–93%, respectively) for con- firming gross invasion of the mediastinum [20–22], but have limited accuracy when invasion is subtle. Definite invasion, however, should be reported. Improvement in determining the extent of chest wall or mediastinal invasion by the primary tumor using PET and PET–CT has not been reported. T4 tumors involve the mediastinum, heart, great vessels, trachea, esophagus, vertebral body, carina, or have a malignant pleural or pericardial effusion (Fig. 2). If the patients have no other contraindication to surgery, some of these tumors represent the one subset within clinical stage IIIB patients who remain good candidates for surgery [23]. Surgical resection of selected tumors involving the left atrium, great vessels, superior vena cava, vertebral body, trachea, and esophagus in selected patients has been shown to Fig. 3. A 72-year-old woman with mucinous adenocar- cinoma of the right upper lobe. Axial CT demonstrates a spiculated right upper lobe mass and satellite nodules in the same lobe. The presence of satellite nodules results in classification of the tumor as a T4 lesion. Fig. 2. An 83-year-old man with adenocarcinoma of the left lower lobe that invaded the descending thoracic aorta (arrow) and left main pulmonary artery, depicted by contrast-enhanced CT. The invasion of these structures results in classification of the tumor as a T4 lesion. non–small cell lung cancer imaging 469have an improved survival [24]. Also of note, the most recent version of the International Staging System states that primary tumors of any size asso- ciated with satellite nodules in the same lobe are also classified as T4 (Fig. 3), whereas nodules in other lobes are classified as metastatic (M1) [2]. Classi- fication of primary tumors with satellite nodules as T4 may imply a worse prognosis than is warranted, and some authors advocate that patients with satellite nodules undergo definitive resection if no other contraindications to surgery exist [25,26]. Malignant pleural effusion can be difficult to diagnose because cytologic evaluation is positive in only approximately 66% of patients [27]. In the absence of cytology- positive fluid, a clinical T4 staging is assigned if there is clinical suspicion of a malignant effusion, which may be raised because of the radiologic appearance [2,28]. PET imaging with 18F-FDG may aid in characterizing pleural disease [29–32]. It is important for the radiologist to indicate the presence of pleural disease in the radiologic report and to correlate CT and PET images when available. The goal of radiotherapy is to treat the tumor adequately with minimal damage to the surrounding normal tissues. As with surgeons, radiation oncolo- gists need to understand the size and location of the primary tumor and proximity of tumor to critical structures, particularly the spinal cord, esophagus, and heart where radiation tolerance imposes dose- volume constraints. Even though current imaging techniques cannot determine the true microscopic limits of tumors, radiologic definition of tumor mar- gins is critical for radiotherapy treatment planning.Radiation oncologists take into consideration imaging limitation of defining tumor margin. Accordingly, the International Commission of Radiation Units and Measurements [33,34] has defined the gross tumor volume as tumor that is visible by any imaging modality; clinical target volume as the volume that is likely to contain microscopic disease based on reported patterns of recurrence; and planning target volume (the area to be irradiated) as the clinical tumor volume with an added margin to account for daily setup error and target motion. Assessment of gross tumor volume is becoming more important in radiotherapy with an increasing use of conformal radiation therapy, which is a technique that uses mul- tiple radiation beams that conform tightly to target volumes and limit damage to surrounding normal structures. As the area around the tumor to be treated is decreased, accurate determination of tumor margin becomes more critical. Underestimation of tumor ex- tent can lead to high local recurrence rates and over- estimation can lead to destruction of normal tissue and complications. Accurate description of tumor margins is needed and at times diagnostic radiologists may assist in delineating gross tumor margins. For those patients treated by medical oncologists, determination of tumor location is important if the patient is at potential risk for a significant complica- tion or potentially life-threatening event, such as invasion into a vascular structure that may lead to exsanguination. The most important radiologic infor- mation for medical oncologists is the assessment of the effectiveness of treatment (whether the disease is stable, improved, or progressed). Determination of disease response is generally done by assessing the munden & bruzzi470primary tumor and metastatic disease for a change in size. To standardize the methods of determining effectiveness of treatment, uniform criteria for report- ing response, recurrence, disease-free interval, and toxicity were adopted at a meeting in 1979 on the Standardization of Reporting Results of Cancer Treatment [35,36]. These criteria, known as the ‘‘World Health Organization criteria,’’ are based largely on tumor measurements in two dimensions (bidimensional), which are obtained by multiplying the longest diameter of the tumor by the greatest perpendicular diameter in the axial plane. This product is the tumor size, and if there are multiple evaluable tumors, then the sum of the products is obtained to determine the total tumor size. Treatment response is defined as complete response (no evi- dence of tumor); partial response (decrease in tumor size by 50%); stable disease (no change in tumor size); or progressive disease (increase in tumor size by 25%) [36]. In 1994, the WHO criteria were revised and guidelines known as the ‘‘Response Evaluation Criteria in Solid Tumors’’ (RECIST) were proposed, whereby tumor measurements are performed with a single measurement (unidimensional), obtained by measuring the longest diameter of the tumor in the axial plane. This measurement is the tumor size, and if there are multiple tumors used, then the sum of the diameters is used to calculate total tumor size. Using RECIST criteria, treatment response is defined as complete response (no evidence of tumor); partialFig. 4. A 73-year-old woman with non–small cell lung cancer of image from a contrast-enhanced CT scan reveals a left lower (long arrow) indicating N1 disease. (B) Image more cephalad re (C) More superiorly, an image demonstrates right lower paratrachresponse (decrease in tumor size by 30%); stable disease (no change in tumor size); and progressive disease (increase in tumor size by 20%). RECIST is now the preferred method of assessing response [37]. Regardless of which criteria are used, new metastatic disease is also indicative of progressive disease and needs to be emphasized. It is important for the radiologist to be aware of these criteria and identify the primary tumor, if present, and any metastatic disease that can serve as measurable disease.Nodal disease The presence and location of regional lymph node metastases (N descriptor) is another important com- ponent of radiologic staging. Accurate assessment of lymph nodes of the mediastinum is essential in selecting the appropriate treatment plan for patients with NSCLC [38]. To standardize the description of nodal metastases, the American Thoracic Society defined nodal stations in relation to anatomic structures or boundaries that can be identified before and during thoracotomy. Although the American Thoracic Society description of nodal stations is the most commonly used system, others, such as that proposed by Naruke et al [39], are also in use, but this article uses the American Thoracic Society system. The presence of nodes within the ipsilateral peribronchial region or hilum indicates N1 disease. N1 lymph nodes can usually be resected at surgery,the left lower lobe and N1, N2, and N3 disease. (A) Axial lobe mass (short arrow) and ipsilateral hilar adenopathy veals subcarinal adenopathy (arrow) indicating N2 disease. eal adenopathy (arrow) consistent with N3 disease. ...