Application of two intensity modulation techniques based on base dose planning function in breast cancer breast-conserving therapy

  Background  The radiotherapy dose of breast cancer patients has great influence on the quality of life after treatment. Based on base dose plan (BDP) function in the Varian Eclipse planning optimization system, two different radiotherapy plans are designed for breast cancer patients with breast conserving therapy, namely, intensity modulated technology and mixed intensity modulated radiotherapy, so as to improve data support for clinical application of BDP function.

  Objective  To compare the dosimetric differences and validation pass rates of breast cancer intensity modulated radiotherapy techniques and hybrid intensity modulated radiotherapy without supraclavicular lymph node prophylaxis based on the BDP function in the Varian Eclipse planning optimization system.

  Methods  From August 2018 to December 2020, 15 cases of female breast cancer without prevention of supraclavicular lymph nodes after breast conserving surgery were treated in the Affiliated Hospital of Jiangsu University, with the age range of 35-65 years. Intensity modulated radiotherapy (IMRT) and hybrid intensity modulated radiotherapy (Hy_IMRT) were designed according to the same CT image, the dose differences of target volume percentage (V95%, V105%), target conformity index (CI) and homegeneity index (HI), the maximum dose (D_max) and mean dose (D_mean), different organs at risk (OAR) and monitor unit (MU) were compared among the two different plans, the BDP function of varian system was used to analyze the pass rate of two validation plans in the 15 breast cancer patients.

  Results  In the Hy_IMRT plan, the planned target volume (PTV) V105%, D_max, D_mean and CI were lower than IMRT (all P＜0.05). Hy_IMRT was higher in terms of D_mean, V20_Gy, V30 _Gy and V40_Gy of the affected lung than those in IMRT (all P＜0.05). The V5_Gy of the left and right lung, the D_mean, V10_Gy and V20_Gy of the heart, the D_mean of healthy breast, and the spinal cord D_max were all significantly lower in Hy_IMRT than those in the IMRT (all P＜0.05), but there was no significant difference in V30_Gy and V40_Gy of the heart (P＞0.05). In terms of MU, Hy_IMRT plan was also lower than IMRT (P＜0.05). Dose verification results showed that the passing rates of the two groups were similar (P＞0.05).

  Conclusion  Compared with Hy_IMRT, IMRT has a higher mean dose in target area and a better advantage in reducing the high dose area which endangers organs, while Hy_IMRT can protect the low dose area which endangers organs and improve the therapeutic efficiency.