life-long routine monitoring is mandatory. Although histopathologic confirmation is the definitive diagnostic method for BC recurrence, it is not always easy to perform as in cases with deeply located or very small-size lesions, or lesion too close to organs or great vessels, making sampling either inaccessible or hazardous. BC recurrence can be assessed using morphological imaging studies or tumor markers. Mammography, ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) are currently the most commonly used morphological imaging methods for detecting breast cancer recurrence. However, both of the two modalities have some restrictions.
Cancer antigen 15-3 (CA 15-3) and carcinoembryonic antigen (CEA) are two tumor markers that are frequently used in the monitoring of BC patients . However, the findings of many studies on these markers in BC follow-up are conflicting.
The introduction of integrated 2-deoxy-2-\[18 F\] fluoro-D-glucose (18FDG) positron emission tomography (PET) computed tomography (CT), known as PET/CT, has become a helpful tool for this purpose.
PET/CT is the functional imaging tool that can measure increased glucose metabolism in cancer cells by using 18F-FDG. Its ability to identify tumor recurrence before detection of morphologic changes in conventional imaging reflecting its importance in detecting BC recurrence in asymptomatic patients with high tumor markers and negative results of radiological imaging. 18F-FDG PET/CT is frequently used for BC evaluation. However, data on its value in evaluating BC recurrence in patients with elevated tumor markers are limited and unclear
