Novel method of radiotherapy planning to improve the dose homogeneity at the junction region for breast cancer

Abstract

AbstractObjectivesThis article introduces a new method to design the radiation therapy planning after radical surgery for breast cancer in order to provide a better homogeneity of the dose distribution in the junction region between the supra clavicular fossa and chest wall.MethodsA total of 15 women who received supra clavicular and chest wall irradiation therapy for breast cancer after radical surgery at Cancer Hospital Chinese Academy of Medical Sciences, Shenzhen Center, Shenzhen, China, between 1 October 2018 and 30 November 2019 were included. The prescription dose was 50 Gy/25 fractions. We designed a new plan on the basis of the original plan for each patient on an Varian Eclipse 13.6 planning system, which added two subfields to each tangential opposing field to change the dose distribution at the junction region. Statistical analysis of the target dose distribution – homogeneity index, conformal index, and irradiation doses to the ipsilateral lung, contralateral lung, heart, left‐side breast, and spinal cord – was carried out for the two groups and the differences were compared.ResultsWhen comparing the two plans, the planning target volume minimum dose (P = 0.04) and planning target volume of the junction region, which was defined as the target in the junction region minimum dose (P = 0.04), homogeneity index (P = 0.02), and conformal index (P = 0.01) for the new method plan were better than those for the original plan. However, there was no statistically significant difference in all dosimetric parameters of the organs at risk (P > 0.05) between the new and traditional method plans .ConclusionBoth plans by new and traditional methods for breast cancer after radical surgery can meet the clinical requirements. The prescription dose coverage, conformal index, and homogeneity index for the target in the new method plan were better than those in the traditional method plan. The new method plan provided a better homogeneity of the dose distribution in the junction region, but had no obvious effect on the dose distribution of the organs at risk. As a result, this new planning method can be used in clinical settings.