The effects of granulocyte colony-stimulating factor on MR images of bone marrow

Abstract

Granulocyte colony-stimulating factor (G-CSF) analogs such as filgrastim/pegfilgrastim are increasingly used to enhance neutrophilic recovery after chemotherapy. It is widely known that, physiologically, pegfilgrastim stimulates marrow mitotic activity and induces marrow reconversion from fatty to cellular. However, there is limited literature discussing the effects of pegfilgrastim on musculoskeletal magnetic resonance imaging, with the consensus that marrow reconversion secondary to pegfilgrastim therapy is easily confounded with a malignant process, especially in patients with a history of cancer. We attempt to discuss the expected changes and MRI findings after pegfilgrastim therapy through a summary of current literature. Additionally, we provide images from our own practice to support the previously established findings. G-CSF-stimulated reconversion can appear as patchy expansions of baseline hematopoietic marrow, but can also appear to be diffusely homogeneous, adding to its ambiguity. We conclude that using a baseline MRI, clinical information, and assessing sequential MRI changes in conjunction with pegfilgrastim therapy may aid the differentiation between benign and pathological change. We expand our discussion to include the effects of novel technologies, such as whole-body MRI, chemical shift imaging, and contrast agents in helping the distinction.

Normal Bone Marrow and Non-neoplastic Systemic Hematopoietic Disorders in the Adult

“…Prominent red marrow reconversion can be seen following treatment with granulocyte colony-stimulating factors (G-CSF), commonly used to manage febrile neutropenia during chemotherapy. 12 Red marrow reconversion has been observed in 40 to 100% of patients undergoing postchemotherapy G-CSF treatment, visible on MRI as soon as 16 days following the onset of treatment. 13,14 No consensus opinion is currently available regarding when exactly marrow reconversion disappears after cessation of treatment.…”

Therapy-Related Imaging Findings in Patients with Sarcoma

“…8-10). 25 Rebound hyperplasia following cessation of chemotherapy can also be seen in the thymus and spleen, resulting in enlargement and increased 18F-FDG uptake up to a year. Marrow reconversion may mimic tumor activity on both MRI and 18F-FDG-PET/CT, up to 4 weeks after termination of G-CSF medication, longer than the period that the blood neutrophil count is elevated.…”

“…Conversely, diffuse BM metastases may be mistaken for rebound red marrow on 18F-FDG-PET/CT because the limited spatial resolution of PET/CT decreases the more granular appearance of bone metastases. 25,28 Normally there is no or very little (< 40%) enhancement on Gd-chelate enhanced images that may assist in differentiating cellular BM from tumor. 29 Diffusion MRI may be especially confusing.…”