Correlation Between Radiation Dose to {sup 18}F-FDG-PET Defined Active Bone Marrow Subregions and Acute Hematologic Toxicity in Cervical Cancer Patients Treated With Chemoradiotherapy

Purpose: To test the hypothesis that radiation dose to {sup 18}F-fluorodeoxyglucose positron emission tomography ({sup 18}F-FDG-PET)-defined active bone marrow (BM{sub ACT}) subregions is correlated with hematologic toxicity in cervical cancer patients treated with chemoradiotherapy. Methods and Materials: The conditions of 26 women with cervical cancer who underwent {sup 18}F-FDG-PET before treatment with concurrent cisplatin and intensity-modulated radiation therapy were analyzed. BM{sub ACT} was defined as the subregion of total bone marrow (BM{sub TOT}) with a standardized uptake value (SUV) equal to or above the mean for that individual. Inactive bone marrow (BM{sub INACT}) was defined as BM{sub TOT} - BM{sub ACT}. Generalized linear modeling was used to test the correlation between BM{sub ACT} and BM{sub INACT} dose-volume metrics and hematologic nadirs, particularly white blood cell count (WBC) and absolute neutrophil count (ANC). Results: Increased BM{sub ACT} mean dose was significantly associated with decreased log(WBC) nadir ({beta} = -0.04; 95% CI, -0.07to -0.01; p = 0.009), decreased log(ANC) nadir ({beta} = -0.05; 95% CI, -0.08 to -0.02; p = 0.006), decreased hemoglobin nadir ({beta} = -0.16; 95% CI, -0.27 to -0.05; p = 0.010), and decreased platelet nadir ({beta} = -6.16; 95% CI, -9.37 to -2.96; p < 0.001). By contrast, there was no association between BM{sub INACT} mean dose and log(WBC) nadir ({beta} = -0.01; 95% CI, -0.06 to 0.05; p = 0.84), log(ANC) nadir ({beta} = -0.03; 95% CI, -0.10 to 0.04; p = 0.40), hemoglobin nadir ({beta} = -0.09; 95% CI, -0.31 to 0.14; p = 0.452), or platelet nadir ({beta} = -3.47; 95% CI, -10.44 to 3.50; p = 0.339). Conclusions: Irradiation of BM subregions with higher {sup 18}F-FDG-PET activity was associated with hematologic toxicity, supporting the hypothesis that reducing dose to BM{sub ACT} subregions could mitigate hematologic toxicity. Future investigation should seek to confirm these findings and to identify optimal SUV thresholds to define BM{sub ACT}.