AR: PET measure may inform lymph node evaluation

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Standardized uptake value (SUV) of regional lymph nodes on PET/CT may provide a threshold to differentiate benign and malignant lymph nodes in patients with inflammatory breast cancer, according to a study published in the May issue of Academic Radiology.  

Inflammatory breast cancer, which accounts for 1 to 5 percent of all breast cancers, is an aggressive disease. Patients are more likely to have metastatic disease at diagnosis and shorter overall survival time, according to Selin Carkaci, MD, from the department of diagnostic radiology at MD Anderson Cancer Center in Houston, and colleagues.  

The authors noted that axillary lymph node involvement is the most significant prognostic factor among these patients. Women with axillary metastasis have shorter disease-free and overall survival than those with node-negative disease. However, anatomic imaging modalities, such as CT, ultrasound and MRI, are limited in their ability to detect metastases in normal-size lymph nodes.

Given these circumstances, Carkaci and colleagues sought to determine if maximum SUV (SUV max) of regional lymph nodes could provide a threshold for identifying nodal metastases.

The researchers conducted a database search to identify all patients newly diagnosed with inflammatory breast cancer who underwent PET/CT between Jan. 1, 2001, and Sept. 30, 2009. Three radiologists blinded to histopathology of the nodes measured SUV max of 888 regional nodal basins in 111 patients.

Of the basins, 70 percent were negative and 30 percent were positive for metastasis. A total of 249 lymph nodes showed increased FDG uptake on visual assessment, and 98 percent of these were malignant, according to Carkaci and colleagues. The malignant nodes had higher SUV max than the benign lymph nodes.

When the researchers compared various SUV max thresholds (2, 2.5 and 3), they found that a maximum cutoff of 2 provided the highest diagnostic accuracy at 89 percent sensitivity and 99 percent specificity.  

“This threshold may help guide biopsy of suspicious regional nodes that may be occult clinically or on routine imaging,” wrote Carkaci et al, before issuing a caveat about image quantification.

“Although SUV is the best method of image quantification, one should be cautious when using SUV alone. Visual assessment by an experienced physician who can consider the clinical context is still critical for real-life practice.”

Carkaci and colleagues offered that a library of lymph node SUVs and cutoffs from a large population of cases might help physicians evaluate borderline cases.

The concluded by noting the potential role of SUV max in the evaluation of metastasis and subsequent therapy planning in women with inflammatory breast cancer.