Long-term follow-up of residual mediastinal-hilar Ga-67 uptake after treatment for Hodgkin's and non-Hodgkin's lymphomas - What degree of Ga-67 uptake is significant?

Purpose: Ga-67 planar and SPECT images of 85 patients after treatment for m ediastinal-hilar (M-H) lymphoma were reviewed retrospectively. Forty-seven patients had Hodgkin's disease and 38 patients had non-Hodgkin's lymphoma. The entire period was 7 years after diagnosis. The main goal was visual ass essment of the significance of mild (grades 1 or 2) Ga-67 uptake in the M-H area as compared with Ga-67 uptake in bone marrow. Methods: Residual Ga-67 mediastinal uptake after a complete course of chemo therapy or other treatments was defined as normal (no residual) M-H uptake, borderline (M-H residual uptake with intensity less than that or equal to the sternum, spine, or both), and abnormal (M-H residual uptake with intens ity greater than that of the sternum or spine). Results: Among the 38 patients (45%) with no residual M-H uptake, four (one Hodgkin's disease and three non-Hodgkin's lymphoma) experienced recurrence : two in the mediastinum and two in the abdomen. Among the 45 patients (53% ) with borderline M-H uptake, five experienced recurrence: two in the media stinum and three in other sites. The two patients (2%) with abnormal (M-H) uptake never responded to treatment. No significant statistical difference in tumor recurrence was found between no residual and borderline uptake (P = 0.21). Conclusions: Visual assessment of M-H Ga-67 uptake (without quantification) could be useful to differentiate active residual tumor from nonactive resi dual uptake.