Seeing into cells. The promise of in vivo molecular imaging in oncology

Abstract

The promise of in vivo molecular imaging in oncology

Figure 1

Example of functional imaging used to measure the response of gastrointestinal stromal tumours (GIST) to imatinib. First column (left) shows a pre-therapy fluorine-18-labelled fluorodeoxyglucose-positron emission tomography (FDG-PET) scan (top) and a contemporaneous computed tomography (CT) scan (bottom). GIST lesions are present in the liver (single arrowhead) and stomach (double arrowheads). There is intense FDG uptake in both lesions. The radioactivity seen in the pelvis is due to normal urinary excretion of the compound. The middle column shows similar scans one month after the start of therapy. The tumour masses are still present, although smaller, on the CT scan but there is no FDG uptake in either lesion. The lack of FDG uptake indicates a biological response to therapy and predicts a long-term beneficial response, despite the tumours being present on the CT scan. Normal collections of radioactivity are present in the urinary bladder and the heart. The third column (right) shows scans one year later. Continued absence of FDG uptake in the liver or stomach indicates an absence of tumour activity. The residual lesions seen on the CT scan are due to scar tissue. Images courtesy of Annick D. Van den Abbeele, Dana Farber Cancer Institute, Boston, MA, USA.

Figure 2

Images illustrating the potential for targeted imaging agents to stratify patients for therapy. Coronal images from two patients (top and bottom rows) of fluorine-18-labelled fluoroestradiol (FES; left column) and F-18-fluorodeoxyglucose (FDG; middle column) uptake before therapy, along with FDG uptake six weeks after hormonal therapy (right column). The patient in the top row is a 44-year-old woman who was previously treated with adjuvant tamoxifen and had a sternal recurrence of breast cancer 4 years later. Her sternal lesion had high pre-therapy FES uptake, which indicated a high level of oestrogen receptors in the tumour (arrowhead; image also shows normal liver and bowel uptake). Such tumours are more likely to respond to hormonal agents such as letrozole. FDG images taken before and after six weeks of letrozole treatment show a significant decline in FDG uptake, with subsequent excellent clinical response. The patient in the bottom row is a 69-year-old woman with newly diagnosed metastatic breast cancer that was not previously treated. Bone metastases were documented by multiple imaging modalities, including FDG-positron emission tomography (PET). Her pre-therapy FES scan showed no uptake in the bone metastases. The patient received multiple letrozole treatments with no response shown by the bone metastases, which is indicated by the post-therapy FDG-PET. (Images courtesy of Mankoff D.. Reprinted from Sem Nucl Med 34: 224–240 with permission from Elsevier.)