Measuring the “Unmeasurable” Assessment of Bone Marrow Response to Therapy Using FDG-PET in Patients with Lymphoma
Received 18 February 2010; accepted 1 May 2010. published online 16 July 2010.
Rationale and Objectives
To determine if anatomically “nonmeasurable” disease in bone marrow (BM) is assessable for response to therapy by [18F]-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET)/computed tomography (CT).
Materials and Methods
FDG PET/CT images of 27 patients with lymphoma, FDG-avid bone marrow (BM) lesions, and ≥1 FDG-avid, tumor-involved lymph node (LN) at baseline were retrospectively reviewed. FDG uptake in target LNs and BM foci was determined pre- and posttherapy using the standardized uptake value corrected for lean body mass (SULmean). Size of the same target LNs was measured pre- and posttherapy on CT. Percentage decreases of LN size and LN and BM SUL were calculated. Response was classified according to revised International Workshop Criteria (IWC) with and without modification for metabolic evaluation of BM and correlated to overall survival. Statistical analyses were performed using paired t-tests, Pearson correlation coefficients, and z-tests.
Results
LN size, LN SULmean, and BM SULmean were significantly higher pre- versus posttherapy (2337 mm2 ± 1810 vs. 309 mm2 ± 323; 6.94 ± 4.96 vs. 1.02 ± 1.00; and 6.81 ± 4.58 to 1.84 ± 1.58, all P < .001, respectively). After therapy, significant correlation was found between percentage declines of LN size and SULmean of LNs (r = 0.84, P < .001) or BM (r = 0.56, P = .002) and SULmean of LN and BM (r = 0.76, P < .001). Including a metabolic assessment of BM correctly altered overall response assessment in 5/27 (19%) patients and better predicted overall survival than revised IWC.
Conclusion
Anatomically “unmeasurable” BM infiltration with lymphoma behaves similarly to LN disease after therapy and is “measurable” by FDG PET/CT. FDG PET/CT is valuable for monitoring tumor response in “measurable” disease and BM, which was previously considered “unmeasurable” by anatomical imaging.
aDivision of Nuclear Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, 601 North Caroline Street, JHOC 3223, Baltimore, MD 21287-0817
Address correspondence to: R.L.W.
Supported in part by a grant from NIH/NCI (3 P30 CA006973-43S2 Abeloff/Wahl for IRAT: Imaging Response Assessment Teams in Cancer Center Supplement).
ABSTRACT