Positron Emission Tomography Imaging for Gastroesophageal Junction Tumors

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Positron emission tomography (PET) is now widely used in the initial evaluation of esophageal and gastroesophageal junction tumors. It can detect otherwise occult metastases, affecting staging and treatment in a significant proportion of patients. The intensity of PET uptake before treatment has been correlated with outcomes, but it remains uncertain whether PET is an independent prognostic factor for survival. An emerging application for PET is the assessment of response to induction chemotherapy or chemoradiotherapy. In particular, PET has the ability to discriminate treatment responders from nonresponders early in the course of induction chemotherapy. This can form the basis for further treatment decisions, such as a change in chemotherapy or the addition of concurrent radiotherapy, and this approach is now being tested in prospective trials. PET after concurrent chemoradiotherapy may also provide information regarding the utility of surgical resection. PET data can affect radiotherapy target definition, which may lead to improved tumor coverage in cases where the true extent of disease is not accurately reflected by computed tomography or endoscopic imaging.

Section snippets

PET for Initial Staging Evaluation

PET is considered a standard part of the staging workup for GEJ cancer owing to its ability to identify distant metastases and therefore incurable disease.1 In newly diagnosed esophageal cancer, it has been shown that 15%-20% of patients will be found to have distant metastases not identified by computed tomography (CT).2, 3, 4, 5 Integrated PET-CT is now widely available and is preferred, as it improves sensitivity compared with PET alone.6

However, the resolution of PET is limited for lesions

PET as an Initial Prognostic Marker

Multiple studies have examined the relationship between initial maximum SUV (SUVmax) and prognosis. Correlation between high SUV and diminished survival has been frequently reported, but whether SUVmax is an independent prognostic factor is less clear. Investigators at Memorial Sloan–Kettering Cancer Center (MSKCC) reviewed 50 patients who underwent surgery without preoperative therapy for esophageal adenocarcinoma and found that patients with SUVmax >4.5 had a 3-year survival of 57%, compared

PET as a Prognostic Marker After Induction Therapy

Because PET imaging can be obtained at various time points in the treatment process, serial scans may provide additional prognostic information based on metabolic response. PET appears to be a more specific marker of favorable treatment response after chemotherapy alone compared with chemoradiotherapy, likely owing to the confounding effect of radiation esophagitis.

In an initial report, German investigators studied 40 patients with GE junction adenocarcinoma who received 12 weeks of

Using PET to Direct Subsequent Treatment

The finding that PET can identify early responders and nonresponders to chemotherapy has prompted interest in using PET imaging to guide the choice of further therapy. Metabolic response evalUatioN for Individualization of neoadjuvant Chemotherapy in Oesophageal and oesophagogastric adeNocarcinoma (MUNICON), a multicenter phase II trial, demonstrated that early metabolic responders to chemotherapy had significantly better event-free survival compared with metabolic nonresponders (29.7 vs 14.1

PET for Radiotherapy Target Delineation

Precise delineation of the primary tumor is often difficult for esophagogastric carcinomas, which are intimately associated with the gastrointestinal mucosa and often lack clear borders detectable with standard cross-sectional imaging. Metabolic imaging with PET may visualize lymph node or submucosal spread of tumor that otherwise would not be visible using CT or endoscopic imaging. Multiple studies have evaluated the role of PET in tumor delineation and radiotherapy planning. However, there is

Conclusion

Because it can detect distant metastatic disease in patients otherwise thought to have curable disease, PET is now indicated in the initial workup of all patients with GEJ cancer. PET also may have prognostic value before, during, and after induction therapy. It is now hoped that PET will lead to therapeutic benefit for patients with localized disease by identifying nonresponders to induction therapy so that they can be switched to an alternate treatment regimen. Because PET can identify areas

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