Abstract
BackgroundTo explore the differences and correlations between the target volumes defined using preoperative prone diagnostic magnetic resonance imaging (MRI) and postoperative prone computed tomography (CT) simulation imaging based on deformable image registration (DIR) for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS).MethodsEighteen breast cancer patients suitable for EB-PBI were enrolled. Preoperative prone diagnostic MRI and postoperative prone CT scan sets for all the patients were acquired during free breathing. Target volumes and ipsilateral breast were all contoured by the same radiation oncologist. The gross tumor volume (GTV) delineated on the preoperative MRI images was denoted as the GTVpreMR and the tumor bed (TB) delineated on the postoperative prone CT images was denoted as the GTVpostCT. The MIM software system was used to deformably register the MRI and CT images.ResultsWhen based on the coincidence of the compared target centers, there were statistically significant increases in the conformity index (CI) and degree of inclusion (DI) values for GTVpostCT-GTVpreMR, GTVpostCT-CTVpreMR + 10, CTVpostCT + 10-GTVpreMR, and CTVpostCT + 10-CTVpreMR + 10 when compared with those based on the DIR of the thorax (Z = − 3.724, − 3.724, − 2.591, − 3.593, all P < 0.05; Z = -3.724, − 3.724, − 3.201, − 3.724, all P < 0.05, respectively).ConclusionsAlthough based on DIR, there was relatively poor spatial overlap between the preoperative prone diagnostic MRI images and the postoperative prone CT simulation images for either the whole breast or the target volumes. Therefore, it is unreasonable to use preoperative prone diagnostic MRI images to guide postoperative target delineation for EB-PBI.
Highlights
To explore the differences and correlations between the target volumes defined using preoperative prone diagnostic magnetic resonance imaging (MRI) and postoperative prone computed tomography (CT) simulation imaging based on deformable image registration (DIR) for external-beam partial breast irradiation (EB-PBI) after breastconserving surgery (BCS)
The patients underwent a lumpectomy, which was performed with a circumferential margin of at least 1.0 cm [19], with sentinel lymph node dissection (SLND) or axillary lymph node dissection (ALND), and tumor-negative margins were ensured during a single operation
The degree of inclusion (DI) and Dice’s similarity coefficient (DSC) median values for the GTVpostCT-GTVpreMR, the GTVpostCT-CTVpreMR + 10, the CTVpostCT + 10-GTVpreMR and the CTVpostCT + 10-CTVpreMR + 10 were generally low; there were statistically significant increases in these parameters based on the center-coincidence of the GTVpreMR and GTVpostCT when compared with those based on the DIR of the thorax (Z = − 3.724, − 3.724, − 3.201, − 3.724, all P < 0.05; Z = -3.724, − 3.724, − 2.591, − 3.636, all P < 0.05, respectively, Table 4)
Summary
To explore the differences and correlations between the target volumes defined using preoperative prone diagnostic magnetic resonance imaging (MRI) and postoperative prone computed tomography (CT) simulation imaging based on deformable image registration (DIR) for external-beam partial breast irradiation (EB-PBI) after breastconserving surgery (BCS). For patients with a low risk of recurrence, accelerated partial breast irradiation (APBI) is gaining acceptance as an alternative to whole breast irradiation (WBI) for early-stage cancer [2,3,4,5,6]. External-beam partial breast irradiation (EB-PBI) is an important approach to APBI. An Italian randomized trial has indicated [7] that the rates of Grades 1 and 2 acute skin toxicity in a APBI cohort were remarkably lower than those in a WBI group with decreases of 17 and 18.2%, respectively. The rates of Grades 1 and 2 toxicity in the EB-PBI patients were significantly higher than those in the WBI group
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