Detection of Minimal Residual Disease in Acute Leukemia by Tc-99m MIBI Femoral Marrow Imaging

Abstract

To determine the potential of Tc-99m MIBI femoral marrow imaging for detecting minimal residual disease in acute leukemia, MIBI images of 68 patients with acute leukemia and 110 control patients were examined. MIBI accumulation was classified into three patterns: not detectable, mild accumulation, and clearly visualized accumulation. Clearly visualized accumulation was interpreted as abnormal. The mean uptake ratio of the femoral marrow to muscle was calculated. Forty-five patients who were in complete remission (CR) at the time of MIBI imaging had a follow-up study (mean interval, 23 months). Clearly visualized accumulation was demonstrated in 35 patients with acute leukemia: in 7 patients before starting induction chemotherapy, in 12 patients after relapse, and in 16 of the 49 patients in the CR group. Mild accumulation was demonstrated in 14 patients in the CR group and in 13 control group patients. No detectable accumulation was observed in 19 patients in the CR group and in 97 control patients. The marrow and muscle uptake ratio of patients before starting chemotherapy (2.29 ± 0.26) was greater compared with that in patients after relapse (1.78 ± 0.44, P < 0.02) and in patients with abnormal accumulation despite complete remission (1.84 ± 0.36, P < 0.01). The uptake ratio in patients with abnormal accumulation despite CR was higher compared with patients with mild accumulation in CR (1.26 ± 0.13, P < 0.001) and controls (1.23 ± 0.10, P < 0.001) who had mild accumulation. Fifteen patients with abnormal accumulation despite CR had a markedly greater relapse rate (66.7% > 10.0%, P < 0.005), a higher mortality rate (46.7% > 6.7%, P < 0.01), and shorter remission time (8.7 ± 10.2 months < 35.9 ± 20.1 months, P < 0.001) compared with 30 patients without abnormal accumulation in CR. MIBI femoral marrow imaging may be a useful and simple method for monitoring levels of residual leukemic cells. Clearly visualized MIBI accumulation may be a marker for relapse.