The volume of (99m)Tc sulfur colloid SPET‐defined active bone marrow can predict grade 3 or higher acute hematologic toxicity in locally advanced cervical cancer patients who receive chemoradiotherapy

BACKGROUND: The purpose of the current study was to evaluate whether radiation dose‐volume metrics to technetium‐99m ((99m)Tc) sulfur colloid single‐photon emission tomography (SPET)‐defined active bone marrow (ABM) subregions can more accurately predict acute hematologic toxicity in locally advanced cervical cancer patients who receive chemoradiotherapy than conventional dosimetric parameters. METHODS AND MATERIALS: Thirty‐nine patients with stage IB2‐III cervical cancer who underwent (99m)Tc sulfur colloid SPET imaging before treatment with cisplatin‐based chemoradiation between January 2017 and March 2018 were analyzed. The total bone marrow (TBM) volume was defined as the external contours of all bones within the vertebral bodies from L4 to the coccyx, the pelvic bones, and the proximal femoral heads. The ABM volume was defined by SPET as the subregion of TBM with a nuclide uptake value greater than or equal to the mean total body nuclide uptake value. Student's t test was used to test for statistical significance between TBM and ABM dose‐volume metrics. Receiver operating characteristic (ROC) curves were generated to compare the predictors of grade 3 or higher (grade 3+) hematologic toxicity. RESULTS: The mean ABM‐V40 (23.22% ± 7.65%) and ABM‐V30 (45.28% ± 9.20%) were significantly lower than the mean TBM‐V40 (33.06% ± 6.72%) and TBM‐V30 (53.08% ± 7.77%), respectively (t = 5.78, P = .001) (t = 4.13, P = .001). The ABM volume (<387.5 cm(3), AUC = 0.928, P = .001), ABM‐V30 (>46.5%, AUC = 0.875, P = .001), and ABM‐V40 (>23.5%, AUC = 0.858, P = .001) can predict the occurrence of grade 3+ hematologic toxicity. Among patients with an ABM volume < 387.5 cm(3), 16/19 (84.2%) had grade 3+ hematologic toxicity compared to 3/20 (15%) with an ABM volume > 387.5 cm(3). CONCLUSIONS: The ABM volume (<387.5 cm(3)) may be a better predictor of hematologic toxicity than conventional dose‐volume metrics, but this finding needs to be further evaluated.