Positron emission tomography (PET) scanning in breast cancer.

Abstract

primary diagnosis, more accurate non-invasive Quantitative analysis techniques include dynamic staging, and more effective methods of following studies which generate absolute glucose metabolic therapy and establishing prognosis. A large number rates and simple relative quantitative ratios, known of new or improved imaging techniques have been as standardized uptake values or SUVs [3, 6]. developed in recent years yet most patients still Simple qualitative visual analysis of the images has require multiple examinations of various organs, also shown high accuracy [6, 7]. including ultrasound of the liver, isotope bone Several studies have examined the initial detecscans, mammograms and CT scans. Furthermore, tion and staging of breast cancer using FDG–PET the current sensitivities and/or specificities of these scans. Wahl and colleagues detected 10 out of 10 methods leave much room for improvement. primary breast lesions and, although these were Positron emission tomography (PET) imaging has generally large lesions (3.2–12 cm), 2 of the patients recently shown promise as a single technique that had dense glandular breast tissue with negative might have equivalent or better accuracy than the mammograms [4]. In a series of 28 patients with other current methods combined [1–4]. 35 suspect breast masses, 27 of which were found The greatest developments in PET imaging to be malignant, Adler et al reported a sensitivity during the 1990s have been in oncology. A number of 90% and specificity of 100% with primary of PET radiopharmaceuticals have been utilized lesions as small as 0.9 cm being correctly identified for oncological investigations including labelled as tumour [8]. In their quantitative analysis, the hormones or their analogues, labelled amino acids, malignant lesions had a mean FDG uptake value labelled hypoxia agents and labelled thymidine [2, (SUV) of 12.8, while benign solid lesions averaged 3]. However, the vast majority of the work to date 1.8 and benign cysts 0.2. Furthermore, there was a has centred on the use of fluorodeoxyglucose labsignificant correlation between normalized FDG elled with Fluorine-18 (18FDG). The 2 h half life uptake and the histological nuclear grade of the not only makes whole body imaging practical but primary lesion. Tse et al from the University of allows for multicentre distribution of tracer. The California at Los Angeles also reported 100% high aerobic glycolytic rate of most tumours means specificity but a false negative rate of 16% [9]. that there is a much higher uptake of FDG in One of their false negative studies had diffuse malignant tissues than in normal tissue. These high microscopic foci and the other had a low grade glycolytic rates are most likely the result of tumour with microscopic foci of invasion. Lesions increased glucose transporter expression and less than 1 cm were detected. While mammography increased hexokinase activity in tumours [2, 3, 5]. was less specific, it was complementary in detecting Moderate levels of hypoxia also increase tumour a FDG–PET negative non-palpable lesion. The glucose uptake rates by 30% or more [5]. Most following year, Nieweg et al from the MD modern PET scanners have large fields of view, Anderson Cancer Center reported a series of 20