Dosimetric analysis of bone marrow-sparing pelvic intensity-modulated radiotherapy after surgery for cervical cancer

Objective: To investigate the effects of bone marrow (BM)-sparing pelvic intensity-modulated radiotherapy (IMRT) alter surgery for cervical cancer on radiation dose to the target volume, organs at risk (OAR), and hematologic toxicity. Methods: Ten patients with cervical cancer who would receive postoperative radiotherapy were selected. BM-sparing pelvic IMRT and conventional IMRT were performed for the same image by the Varian planning system. The radiation dose to the pelvis, the dose distribution of the target volume, and the radiation dose to OAR were compared between the two plans. A total of 30 patients with cervical cancer who had received postoperative radiotherapy were selected to investigate the relationships of the radiation dose to the pelvis with the lengths of the pelvis in coronal axis, sagittal axis, and vertical axis and the pelvic volume. A total of 41 patients with cervical cancer who would receive postoperative radiotherapy were randomly divided into observation group and control group. The observation group was given BM-sparing IMRT, while the control group was given conventional IMRT. The incidence of grade ≥ 2 hematologic toxicity was compared between the two groups and the relationship between the hematologic toxicity and the radiation dose to the pelvis was investigated. Results: Both groups showed excellent dose coverage to the clinical target volume. There was no significant difference in radiation dose to the OAR between the two groups (all P > 0.05). However, the observation group had significantly lower D_mean, V₁₀, V₂₀, V₄₀, and V₅₀ of the pelvis than the control group (P = 0.003-0.045). The Pearson correlation analysis showed that D_mean, V₂₀, V₃₀, V₄₀, and V₅₀ of the pelvis were negatively correlated with the length of the pelvis in coronal axis (P = 0.008-0.038). The observation group had a significantly lower incidence of hematologic toxicity than the control group (P = 0.019). The logistic regression analysis showed that the development of hematologic toxicity was significantly associated with V₂₀ of the pelvis (OR = 1.191, P = 0.042). Conclusions: BM-sparing IMRT after surgery for cervical cancer can reduce the radiation dose to the pelvis and the incidence of blood toxicity. The radiation dose to the pelvis is negatively correlated with the length of the pelvis in coronal axis. The development of hematologic toxicity is associated with V₂₀ of the pelvis. (authors)