FDG-PET Superior to CT and MRI in Detecting Lymph Node Metastases in Neck

FDG-PET Superior to CT and MRI in Detecting Lymph Node Metastases in Neck

In patients with squamous cell cancer of the mouth, imaging with fluorodeoxyglucose positron emission tomography (FDG-PET) detected more hidden lymph node metastases in the neck than computed tomography (CT) or magnetic resonance imaging (MRI). These results were published in the Journal of Clinical Oncology.

Oral cancer refers to cancer that involves the mouth, lips, or tongue. A majority of cases of oral cancer are linked with tobacco use. High alcohol intake also increases the risk of oral cancer.

Because oral cancer can spread to lymph nodes in the neck, treatment of oral cancer may involve surgical removal or irradiation of these lymph nodes. While it would be optimal to reserve lymph node treatment for those patients with lymph node metastases, it can be difficult to determine in advance whether lymph node metastases are present. Some lymph node metastases are too small to be felt. They may also be missed by conventional imaging techniques such as computed tomography (CT) or magnetic resonance imaging (MRI).

To determine whether an alternative imaging technique-FDG-PET-can be used to identify hidden lymph node metastases in the neck, researchers in Taiwan conducted a study among 134 patients with oral cancer. None of the patients had lymph node metastases that could be felt by palpating the neck. Before surgical removal of the lymph nodes of the neck, patients underwent imaging with FDG-PET and CT or MRI.

  • Surgery detected lymph node metastases in 26% of the patients.
  • FDG-PET detected more lymph node metastases than CT or MRI. FDG-PET detected 51% of patients with lymph node metastases, compared to 31% for CT or MRI.
  • Overall, the probability of a false-negative result using FDG-PET was 6.7% for patients with T1 tumors (tumors smaller than 2 cm); 10.8% for patients with T2 tumors (tumors between 2 cm and 4 cm); 13.3% for patients with T3 tumors (tumors larger than 4 cm); and 25% for patients with T4 tumors (tumors that invade nearby tissue).

The researchers conclude that FDG-PET was superior to CT or MRI for detecting hidden lymph node metastases in the neck. The performance of FDG-PET was not perfect, however; it produced false-negative results in up to 13% of patients with T1-T3 tumors. In patients with T4 tumors, it produced false-negative results in 25% of patients.

Reference: Ng S-H, Yen T-C, Chang T-C et al. Prospective Study of [18F] Fluorodeoxyglucose Positron Emission Tomography and Computed Tomography and Magnetic Resonance Imaging in Oral Cavity Squamous Cell Carcinoma with Palpably Negative Neck. Journal of Clinical Oncology. 2006;24:4371-4376.

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