MR-IMAGING OF BONE-MARROW IN CHILDREN WITH OSTEOSARCOMA - EFFECT OF GRANULOCYTE-COLONY-STIMULATING FACTOR

OBJECTIVE. Granulocyte colony-stimulating factor (GCSF) is used to Sti mulate myeloid cell production and function in children undergoing che motherapy for osteosarcoma. We hypothesize that GCSF can cause reconve rsion of marrow from fatty to hematopoietic and that this change can b e detected by MR imaging at sites away from the primary tumor. This be nign effect of treatment should not be confused with tumor spread. MAT ERIALS AND METHODS. MR images of marrow of the affected and contralate ral limbs were retrospectively reviewed for 16 patients with osteosarc oma of the femur or tibia; nine of these patients had received GCSF A grade was assigned to marrow signal intensity at sites away from the t umor, and findings before and after treatment were compared. The valid ity of MR image interpretation was assessed by comparing the signal in tensity of marrow with the histologic appearance of marrow at 19 resec tion margins. RESULTS. Changes consistent with reconversion were seen on MR images in seven of nine patients who had received GCSF in additi on to chemotherapy and in none of seven patients who had received chem otherapy alone. The difference in proportions was statistically signif icant (p = .006; Fisher's exact test, two tailed). The histologic appe arance of marrow at the resection margins agreed with the interpretati on of the short-TI inversion recovery sequence in all cases (100%). CO NCLUSION. The findings suggest that GCSF causes changes in the MR imag ing appearance of marrow. Histologic correlation supports the hypothes is that these changes are attributable to reconversion from fatty to h ematopoietic marrow. Awareness of this finding is important to avoid f alse-positive diagnosis of marrow metastases.