[Scintigraphy in staging upper aerodigestive tract epidermoid carcinomas]

To determine the value of technetium-99m bone scintigraphy in the screening of bone metastases in the systematic initial extension assessment of upper aerodigestive tract suamous cell carcinomas; to identify risk factors of these bone metastases for better screening.

In this prospective study, the initial assessment of tumoral extension was systematically associated with bone scintigraphy. Only patients with no malignant tumors were included in the study. Any skeletal fixation identified was then analyzed with standard radiography and/or tomodensitometry and with the patient's clinical progression to confirm whether or not the fixation was metastatic. The sensitivity and specificity of bone scintigraphy was then calculated. A correlation between bone pain or hypercalcemia and confirmed bone metastases was also systematically sought to determine whether these factors were predictive of bone metastases so as to better target the screening.

Among the 55 patients included in the study, three had confirmed bone metastases. All were detected by the bone scintigraphy, with a sensitivity of 100%. However, the 20 false-positive results gave a low specificity of 62%. Bone pain was described by two patients, but they were among the three metastatic patients. Specificity was 100%, but the sensitivity was only 67%. Three patients had hypercalcemia: the three metastatic patients. The sensitivity and specificity were 100%. In the tumoral status of the three patients with bone metastasis, tumors were small, classified as T1 or T2, but with substantial node involvement, classified N3, and with invasion of the internal jugular vein in two cases.

The incidence of bone metastases in the initial extension assessment was low; consequently, they are not sought systematically. However, their presence radically changes the prognosis and the therapeutic management, raising the question of screening. The technetium-99m bone scintigraphy has limits, with many false-positive resulting the need for additional investigations. Defining the risk factors for bone metastases would improve screening. Two questions remain: what factors are involved? The bone pain and the hypercalcemia must be analyzed with a larger number of cases, but they seem to be nonspecific. The node involvement stage could be a more reliable parameter, in particular in cases of jugular vein invasion; what method should be used? In the future, the PET scan could be the key procedure not only in the locoregional extension assessment, but also for general extensions, in a single procedure investigating the whole body.