Bingxu.TAN
Purpose: This study aimed to evaluate the differential effects of helical tomotherapy (TOMO) and intensity-modulated radiation therapy (IMRT) on bone marrow suppression and assess the efficacy of prophylactic PEG-rhG-CSF in preventing neutropenia during concurrent chemoradiotherapy (CCRT) for pelvic malignancies.
Methods: In this multicenter randomized phase III trial, 240 patients with cervical, rectal, or bladder cancer were stratified by radiotherapy modality (TOMO vs. IMRT) and randomized to receive prophylactic PEG-rhG-CSF (6 mg, 48 hours post-chemotherapy) or reactive management. Primary endpoints included grade 3–4 neutropenia incidence, pelvic bone marrow (PBM) dose-volume parameters (V10, V20, V30), and febrile neutropenia (FN) rates. Secondary endpoints encompassed treatment delays, hospitalization events, and 2-year overall survival (OS).
Results: TOMO demonstrated superior bone marrow sparing, with significantly lower V20 (32% vs. 48%, P<0.001) and V30 (18% vs. 29%, P=0.003) compared to IMRT. Prophylactic PEG-rhG-CSF reduced grade 3–4 neutropenia rates in both TOMO (12% vs. 40%, P<0.001) and IMRT groups (25% vs. 58%, P<0.001). FN incidence was lowest in the TOMO+PEG-rhG-CSF cohort (3% vs. IMRT+control: 20%, P<0.001). Treatment delays due to myelosuppression were reduced by 68% with prophylaxis (HR=0.32, 95% CI: 0.15–0.65).
Conclusion: Prophylactic PEG-rhG-CSF effectively mitigates neutropenia risk in pelvic CCRT, particularly in IMRT-treated patients with higher bone marrow exposure. TOMO’s dosimetric advantages support its integration into marrow-sparing protocols.