Bone marrow function in cervical cancer patients after concurrent chemoradiotherapy using 99mTc-SC SPECT/CT: A...

99mTc-sulfur colloid (99mTc-SC) single-photon computed emission tomography/computed tomography (SPECT/CT) bone marrow (BM) scintigraphy is a key diagnostic tool for distinguishing active red BM from inactive yellow BM. Although previous research has documented that it could reduce the volume of ABM irradiated at higher doses, the role of SPECT/CT parameters in assessing BM function in different pelvic regions and in predicting hematologic toxicity (HT) remains underexplored. This study aimed to investigate the value of 99mTc-SC SPECT/CT imaging for assessing BM function and its predictive role for HT in patients with cervical cancer undergoing concurrent chemoradiotherapy (CRT). In this retrospective study, 40 patients with stage IB2-IVA cervical cancer underwent 99mTc-SC SPECT/CT before and within 2 weeks after CRT. Patients were stratified into BM suppression (BMS) and non-BMS groups based on grade ≥ 3 HT. Semi-quantitative uptake ratios (R, liver-normalized) and their changes (ΔR) across 5 pelvic sites (L4, L5, sacrum, ilium, pubis) were compared. Analyses incorporated False Discovery Rate correction for multiple comparisons, non-parametric sensitivity tests, and effect size reporting. Predictive performance for HT was assessed using receiver operating characteristic curves and internally validated via leave-one-out cross-validation. CRT induces a spatially heterogeneous suppression of BM function, predominantly affecting the lumbosacral region. Elevated semi-quantitative uptake on pretreatment 99mTc-SC SPECT/CT, particularly in the lumbosacral region, exhibits potential as a biomarker for predicting severe HT. These findings underscore the promise of functional imaging for personalized risk stratification, pending validation in larger, prospective, multi-institutional cohorts. Post-CRT reduction in BM uptake (ΔR) was significantly more substantial within the lumbosacral spine (L4, L5, Sacrum) compared to the pelvic bones (Ilium, Pubis), with a moderate overall effect (partial η2 = 0.156). Patients who developed grade ≥ 3 HT (BMS group) exhibited significantly higher pretreatment R values and greater ΔR declines in the lumbosacral spine compared to the non-BMS group, with large effect sizes (e.g., Cohen d up to -1.05). Pretreatment R values at L4 (area under the curve [AUC] = 0.769), L5 (AUC = 0.767), and sacrum (AUC = 0.793) were significant predictors of grade ≥ 3 HT, a finding affirmed by leave-one-out cross-validation (cross-validated AUCs: 0.724, 0.737, and 0.752, respectively).