18F-NaF PET in Detecting Metastatic Bone Lesion for Patients With Cancer.

Skeletal metastases are the most common cause of morbidity and mortality in patients with malignancy, especially in patients with breast cancer, lung cancer, prostate cancer and head & neck cancer. In patients with lung cancer, bone metastases are present in 20-30% of patient at initial diagnosis (1-2). Accuracy staging bone metastases can lead to modification of following treatment and evaluation of prognosis.

The planar whole-body 99mTc-methylene diphosphonate (MDP) radionuclide bone scintigraphy is the most widely used technique in detecting metastatic bone lesions at present. Abnormal tracer accumulation may occur at any skeletal site with an elevated rate of bone turnover. However, conventional planar bone scintigraphy was reported to be less sensitive than MRI in detecting spinal metastases (3-7).

18F ion is a positron emitting bone radiopharmaceuticals. The skeletal uptake of 18F relies on the exchange of hydroxyl ions in the hydroxyapatit crystal which is an indicator of bone metabolic activity (8). It has good soft tissue clearance and high affinity of to the bone matrix. It is able to perform a highly sensitive whole-body screening for bone metastases using a high resolution PET scanner.

To the best of our knowledge, there are only limited studies evaluating the clinical utilization of 18F-NaF PET for detection of bone metastases (10-12). Therefore, we would like to conduct a prospective study to evaluate the accuracy and clinical value of 18F PET in staging bone metastases by

1. Comparing the sensitivity of 18F-NaF PET with that of 99mTc-MDP scintigraphy;
2. Determining the clinical impact of PET results on subsequent patient management.

99mTc-MDP scintigraphy and 18F PET will be performed in 2 weeks for all patients. Interpretation of 99mTc-MDP scintigraphy and 18F PET will be performed following the criteria described by Crasnow et all (13). The accuracy of 99mTc-MDP scintigraphy and 18F PET detection of bone metastases for each patient will be determined by the histopathological results, MRI results, or other clinical evidences afterward.