Objective To explore the relationship between bone marrow suppression and the dose volume of iliac irradiation in postoperative cervical cancer patients that received intensity-modulated radiotherapy (IMRT).

Methods A total of 109 postoperative cervical cancer patients that received IMRT were enrolled in this study from January 2013 to January 2016. The patients were divided into bone marrow sparing–intensity-modulated radiotherapy (BMS-IMRT)56 cases (including 31 patients who received radiotherapy alone and 25 patients who received concurrent radiotherapy and chemotherapy), aged (43.03 ± 4.49) years and IMRT (53 cases (including 21 patients who received radiotherapy alone and 32 patients who received concurrent radiotherapy and chemotherapy), aged (42.72±5.23) years) groups. The bone marrows from the patients in both groups were delineated on the planning system, including bone marrows from the lumbosacral vertebra, iliac bone, ischium, pubic bone, and proximal femur. The dose of bone marrow was limited in the BMS-IMRT group only. The relationship of dose distribution in the target area of the treatment plan, irradiation volume and dose of bone marrow, the irradiation volume of bone marrow and the bone marrow suppression during radiotherapy between two groups were observed. Measurement data, such as planned target volume dosimetry and the dose-volume parameters of organ at risk, were expressed as mean ± standard deviation. All data conformed to a normal distribution. The comparison between the groups was performed using t-test. Chi-square test was applied to the comparison of the groups in terms of counting data, such as the comparison of bone marrow suppression, leukocyte and neutrophil reduction, and other adverse reactions.

Results The degree of bone marrow suppression was significantly related to irradiation volume and dose. No significant difference in PTV dosimetry was found between the BMS-IMRT and IMRT groups (t=−4.220−2.923, all P >0.05). Significant differences in the V₂₀ (the volume percentage of the total volume≥20 Gy) and V₄₀ (the volume percentage of the total volume≥40 Gy) of bone marrow, V₄₅ (the volume percentage of the total volume≥45 Gy) and D_2% (approximate maximum dose) of the rectum, and D_2% of the small intestine were found between the groups (t=−12.696−2.917, all P<0.05). Significant differences of hemamebas and neutrophils reduced between two groups (χ²=6.728, 6.813, P=0.035, 0.033). No significant differences in red blood cell and hemoglobin levels were found between the groups (χ²=0.385, 0.006, 1.419, P=0.825, 0.938, 0.492). In patients that underwent radiotherapy alone, difference in the degree of reduction in leukocyte level between the two groups was statistically significant (χ²=9.709, P=0.008). By contrast, no significant difference was found in patients that underwent concurrent radiochemotherapy (χ²=0.073, P=0.786), and the degree of neutrophil decrease was not statistically significant between the two groups (χ²=4.171, 1.523, P=0.093, 0.217). Moreover, differences in other adverse reactions between the two groups were nonsignificant (χ²=0.369, 1.845, 1.158, 0.610, P=0.544, 0.398, 0.560, 0.558).

Conclusions Reduction in leukocyte and neutrophil levels during pelvic IMRT after radical operation for cervical cancer is positively correlated with bone marrow irradiation dose and volume. Bone marrows within the irradiation range should be outlined, including those in the lumbosacral vertebrae, iliac bones, ischium, pubic bone, and proximal femur, and should be protected by limiting irradiation dose.