FDG-PET/CT helps assess pulmonary lymphangitic carcinomatosis

Friday, December 4 | 11:30 a.m.-11:40 a.m. | SST12-07 | Room S505AB
FDG-PET/CT has high specificity for detecting pulmonary lymphangitic carcinomatosis (PLC), while FDG-PET alone can miss focal PLC in close proximity of primary cancer. Those conclusions will be presented by researchers from Massachusetts General Hospital (MGH) in Boston, who observed that FDG-PET showed "significant uptake" in the area of PLC and aided in more accurate diagnoses.

"In our study, we used FDG-PET/CT with which the anatomic and metabolic data can be acquired in the same setting," said co-author Priyanka Prakash, research fellow at MGH. "It thus provides precise localization of suspicious areas of increased FDG uptake unlike the previously used FDG-PET alone. Moreover, measuring the [standardized uptake value (SUV)] and using the cutoffs for abnormal uptake increases the specificity of diagnoses."

The retrospective analysis reviewed 35 patients with PLC confirmed with follow-up chest CT scans or histopathology. Standardized uptake values were measured in the affected lung, the contralateral normal lung, and the mediastinal blood pool based on patient's body weight and the initial injected activity.

A visually identifiable increase in SUV in the region of pulmonary lymphangitic carcinomatosis was discovered in 86% of patients.

As for FDG-PET's inability to locate focal PLC in close proximity of the primary cancer, Prakash said there is no way to correct for that omission.

"This only suggests that the radiologist should carefully assess the areas of close proximity to the primary lung malignancy on the CT scan for possible lymphangitic spread of the tumor, even if there was no corresponding area of increased uptake on the PET/CT," Prakash added. "However, clinically it is the distant PLC which is more important, as its presence would change the staging of lung cancer to stage 4, which is inoperable and thus would have entirely different treatment approach, unlike focal PLC, which does not change the tumor node metastasis staging of lung cancer."

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