Gallium scan in the evaluation of post chemotherapy mediastinal residual masses off aggressive non-Hodgkin's lymphoma

Optimal evaluation of residual masses of non Hodgkin's lymphomas (NHL) afte r chemotherapy is of major importance, and gallium scan (GS) is routinely u sed for this purpose, particularly for mediastinal sites. However, sensitiv ity and specificity of GS in this setting has been diversely appreciated an d needs to be more accurately defined especially if radiotherapy is not pla nned. A retrospective analysis selected all the patients treated in a singl e institution for aggressive NHL who presented a residual mass in the media stinum after chemotherapy and who were evaluated by GS. The value of GS for distinguishing true complete responses (CR) from partial responses (PR) wa s analyzed in patients who were either submitted to resection of their resi dual mass or followed up without further treatment after GS. A residual mas s with mean perpendicular diameters measuring 4.1 cm x 2.8 cm was found in 42 patients and was GS positive in 8 cases and negative in 34 cases. After GS, radiotherapy was delivered to 10 patients, but 12 patients underwent re section of their residual mass and 20 were followed up without further trea tment. In the patients who did not receive radiotherapy, 3 false positive a nd 6 false negative GS results were disclosed. The specificity and the sens itivity of GS were 88% and 25%, and its positive predictive value and negat ive predictive value 40% and 78%, respectively. GS was not sufficiently rel iable to evaluate post chemotherapy residual masses. Surgical resection of residual masses should be considered particularly in young patients. Patien ts in true CR should be spared pointless radiotherapy and its late side eff ects, while patients in PR may benefit from further intensified chemotherap y followed by radiotherapy.