Introduction

The anatomical imaging techniques of computer tomography (CT) and endoscopic ultrasound (EUS) have limitations in the staging of esophageal cancer, in assessing response to therapy, and in predicting survival. Functional imaging using positron emission tomography (PET) has been shown to provide unique information in other tumors and is increasingly being used in oesophageal cancer.

Positron emission tomography

PET is an imaging technique that can map functional activity before structural changes have taken place and has established a recognized place in imaging cancer. The most commonly used isotope at the present time is 18F-fluoro-2-deoxy-d-glucose (FDG), which can differentiate malignant from normal tissue based on the enhanced glucose transport and glycolysis exhibited by many tumor cells. FDG is a glucose analogue, and both FDG and glucose are taken up by cells via the membrane glucose transporter system and are phosphorylated by hexokinase. Unlike glucose, FDG-6-phosphate does not cross the cell membrane and is trapped in cells and is visualized. It can be dephosphorylated, but this is a slow process particularly in cancer cells that lack or have reduced levels of glucose-6-phosphatase. FDG accumulation depends on the rate of transport through the cell membrane that is mediated by glucose transporters (GLUT). Many malignant cells, including gastrointestinal tumors, show increased expression of GLUT-1, contributing to increased FDG accumulation, and this correlates with tumor invasiveness and poor survival in some cancers.

Introduction: Why stage disease?

The staging of renal tumors is important as it divides them into groups that enable a logical framework for treatment planning, entry into clinical trials, and prognostication. With the increasing use of techniques such as nephron-sparing surgery and laparoscopic surgery the radiological staging information will determine the type of surgical approach. Also, unlike surgery which provides tissue for pathological staging, ablative therapies such as cryotherapy or radiofrequency ablation rely solely on radiological staging, with the occasional benefit of renal biopsy.

History of staging

The first staging system for renal tumors was introduced by Flocks and Kadesky in 1958 and subsequently modified by Robson in 1963. The TNM criteria was introduced in 1978 and revised in 1987, 1997, and most recently in 2002 (Table 5.1). These modifications reflected a change in surgical approach and better understanding of the survival characteristics of the different groups.

The 1997 AJCC (American Joint Committee on Cancer) revision resulted in reclassification of T1 lesions from confined tumors less than or equal to 2.5 cm to those lesions 7 cm or less. Confined tumors measuring greater than 7 cm were classified as T2. A subsequent study demonstrated an 83% 5-year survival for T1 tumors with a 57% 5-year survival for T2 tumors. This major difference in prognosis underlies the rationale for the division between T1 and T2 tumors.

Esophageal cancer is a relatively uncommon but highly lethal malignancy. The incidence of adenocarcinoma is rapidly increasing, and improved survival will depend on prevention, earlier diagnosis, improved staging, and appropriate treatment.

As is the case with other malignancies, it is the multidisciplinary team approach toward patient care that determines the appropriate management of patients with esophageal cancer. For this approach to be effective, it is essential for all members of the multidisciplinary team to understand the role of imaging in esophageal cancer, its advantages, and limitations. Equally, it is vital for the radiologist to appreciate the clinical context of the imaging.

This volume provides a detailed review of new endoscopic methods of diagnosis, staging using both conventional and functional imaging, and assessment of surgical and medical methods of therapy.