Follow-up of mediastinal lymphoma: role of ultrasonography

Patients with lymphoma are often young and require long and intensive treatment, the toxic effects of which compound the impact of frequent radiological examinations. Computed tomography (CT) is of great value in the evaluation of the mediastinum, which is frequently involved by the disease, but carries a high radiation load. Ultrasonography (US) has therefore been proposed as an alternative procedure to evaluate response to treatment. Major advantages include good compliance, absence of patient risks, low cost, easy reproducibility, dynamic images enabling multiplanar evaluation and qualitative and quantitative criteria. The purpose of this study was to investigate the role of US in evaluating response to treatment in patients with mediastinal lymphomas using CT as the gold standard.

In 2005, 12 patients were evaluated by chest X-ray, mediastinal sonography and contrast-enhanced CT (gold standard). Each mediastinal region was accurately assessed for adenopathies. Lymph nodes were studied by evaluating their structure and morphology, measuring their size and classifying them according to location.

US proved to be more sensitive and accurate (93%) than X-ray [66% sensitivity and 68% diagnostic accuracy (DA)]. In particular, the best sensitivity values were observed in the supraaortic (97% vs. 55%), prevascular (97% vs. 39%) and paratracheal (87% vs. 77%) regions and in the aortopulmonary window (80% vs. 0%). Deeper mediastinal compartments (subcarinal region and posterior mediastinum) could not be assessed. X-ray proved to be superior in hilar adenopathies only. US provides qualitative information (hypoechoic or hyperechoic tissues) in addition to quantitative data (maximum diameter of each lymph node) it shares with CT. DISCUSSION.: Compared with X-ray, US allows for a better evaluation of the anterior mediastinal regions, showing small, central adenopathies that do not alter the mediastinal lines on X-ray. It is, however, of very limited value in the evaluation of posterior compartments because of their deep location. US adds qualitative criteria to the quantitative criteria typical of CT. Limitations of mediastinal US include site of adenopathies, dependence on the patient's characteristics (body habit, concurrent diseases and chest anatomy) and dependence on the operator.

US may have a specific role in monitoring patients with mediastinal adenopathies, providing early indications on possible response to treatment and allowing the frequency of CT follow-up scans to be reduced. In conclusion, US may be used to complement, but not replace CT, which remains the gold standard.