Esophageal Cancer: Role of Imaging in Primary Staging and Response Assessment Post Neoadjuvant Therapy
Introduction
Esophageal cancer is the eighth most common malignancy worldwide with 456,000 new cases diagnosed in 2012.1 Rates have risen by 65% in men and 14% in women since the mid 1970s. In the UK, the incidence rate is the second highest in Europe for men and the highest for women. Although it is a leading cause of mortality (sixth most fatal cancer globally), survival rates have been improving with now approximately 20% surviving at least 5 years after diagnosis for all stages of esophageal cancer.1
Precise pretreatment staging of esophageal cancer is essential to determine which patients are suitable for surgery and to help formulate the optimal treatment plan. This minimizes inappropriate treatment and results in better clinical outcome. Computed tomography (CT), endoscopic ultrasound (EUS), and positron emission tomography-computed tomography (PET-CT) are all considered complementary modalities in the preoperative staging and therapeutic monitoring of esophageal cancer. This article reviews their clinical utility and relative strengths and weaknesses.
Section snippets
Histologic Types of Esophageal Cancer
More than 90% of esophageal cancers are either squamous cell carcinomas (SCCs) or adenocarcinomas. SCCs are linked to tobacco and alcohol abuse, whereas adenocarcinomas are highly associated with obesity and gastroesophageal reflux disease. SCC has historically been more prevalent than adenocarcinoma. However, over the last few decades, there has been an unexplained shift in histologic type and primary tumor location with a dramatic rise in rates of adenocarcinoma in the United States and
TNM Staging of Esophageal Cancer
Accurate staging of esophageal cancer requires an innate understanding of the pattern of tumor spread. Radiologists need to be familiar with the seventh edition of the TNM staging system (Table 1) as developed by American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC).7 This has made significant changes to the sixth edition with new definitions for the anatomical classifications of Tis, T4, N (regional lymph node), and M (distant metastasis) together with
Treatment of Esophageal Cancer
In the absence of metastatic disease, localized tumors (T1 and T2) have a high likelihood of R0 resection. In patients with stage I disease, especially Tis and T1aN0, endoscopic mucosal resection or endoscopic submucosal dissection can be considered, where local expertise is available. Primary oesophagectomy can be performed in patients with T1b (and any N) disease. For patients with T2 and T3 disease, trimodality treatment is now recommended, if tolerated, which involves neoadjuvant
T Staging
The CT provides the primary noninvasive method for staging esophageal cancer. Water (eg, 750 mL) can be given orally just before the CT scan to distend the esophagus, although the volume ingested may be limited by dysphagia. A distended esophagus has a normal wall thickness of 3 mm. Greater than 5 mm is considered abnormal. The CT defines the site of primary tumor. The esophagus is divided into the following 4 regions for purpose of classification and staging: cervical, upper thoracic,
Role of Imaging in the Assessment of Therapeutic Response
Neoadjuvant chemoradiotherapy is becoming more routinely used in patients with stage IIB and stage III disease. The aim is to treat coexistent micrometastases and downsize the primary tumor. Patients who demonstrate a major histopathological response (regression to less than 10% of the primary tumor) after preoperative treatment show improved survival. On current treatment regimes, 40%-50% of patients show a major histopathological response. The remaining cohort does not benefit from this
Interpretative Pitfalls in Assessing Treatment Response With PET-CT
The CT acquisition is performed with the patient in suspended expiration, whereas the PET images are acquired in quiet breathing. This results in slight misregistration of the fused PET-CT images and therefore discrepancies in the calculation of the SUVmax. This is most problematic at the level of the diaphragm where SUVmax can vary by up to 30%-50%.68 Hence, changes in SUVmax between baseline and follow-up PET-CT post neoadjuvant treatment in distal esophageal or gastroesophageal cancers in
Conclusions
The CT, EUS, and PET-CT all have important contributions in the initial staging and restaging post neoadjuvant treatment in patients with esophageal cancer.
The CT is required for the initial staging following confirmed histologic diagnosis of malignancy. The MDCT benefits from use of thin slices and multiplanar reformats. The EUS is the best test for assessing depth of tumor invasion and regional nodal involvement. The PET-CT is helpful for assessing distant metastatic disease but is of limited
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