Treatment-Induced Bone Marrow Enhancement at MRI in Breast Cancer Patients Receiving Granulocyte-Colony Stimulating Factor Adjunct to Chemotherapy

Rationale and Objectives: Granulocyte-colony stimulating factor (G-CSF) induces the reconversion of fatty bone marrow to hematopoietic bone marrow. The bone marrow changes are detectable as signal intensity changes at MRI. The aim of this study was to evaluate sternal bone marrow enhancement following G-CSF and chemotherapy treatment in women with breast cancer. Materials and Methods: This retrospective study included breast cancer patients who received neoadjuvant chemotherapy with adjunct G-CSF. The signal intensity of sternal bone marrow at MRI on T1-weighted contrast-enhanced subtracted images was measured before treatment, at the end of treatment, and at 1-year follow-up. The bone marrow signal intensity (BM SI) index was calculated by dividing the signal intensity of sternal marrow by the signal intensity of the chest wall muscle. Data were collected between 2012 and 2017, with follow-up until August 2022. Mean BM SI indices were compared before and after treatment, and at 1-year follow-up. Differences in bone marrow enhancement between time points were analyzed using a one-way repeated measures ANOVA. Results: A total of 109 breast cancer patients (mean age 46.1 ± 10.4 years) were included in our study. None of the women had distal metastases at presentation. A repeated-measures ANOVA determined that mean BM SI index scores differed significantly across the three time points (F[1.62, 100.67] = 44.57, p < .001). At post hoc pairwise comparison using the Bonferroni correction BM SI index significantly increased between initial assessment and following treatment (2.15 vs 3.33, p < .001), and significantly decreased at 1-year follow-up (3.33 vs 1.45, p < .001). In a subgroup analysis, while women younger than 50 years had a significant increase in marrow enhancement after G-CSF treatment, in women aged 50 years and older, the difference was not statistically significant. Conclusion: Treatment with G-CSF as an adjunct to chemotherapy can result in increased sternal bone marrow enhancement due to marrow reconversion. Radiologists should be aware of this effect in order to avoid misinterpretation as false marrow metastases.