Can intensity-modulated radiation therapy spare the central flapped area while encompassing the target volume in radiotherapy after immediate breast reconstruction?

Abstract

Radiotherapy increases the morbidity of immediate breast reconstruction. To spare the flapped area without an adverse dose distribution of the target volume and organ at risks, various radiation techniques were assessed. Twelve breasts undergoing skin-sparing mastectomy and immediate transverse rectus abdominis myocutaneous flap reconstruction were evaluated. After a delineation of whole breast, the doughnut-like breast target volume (BTV) including the chest wall and skin and the subtracted central flapped volume (FV) were defined. The opposed wedge tangential radiotherapy (3-dimensional conformal radiotherapy (3-D CRT) ), field-in-field radiotherapy (FiF), inverse intensity-modulated radiotherapy (iIMRT), volumetric modulated arc radiotherapy (VMRT) and the mixture of FiF and iIMRT (HYBRID) were tried. Total 50 Gy was prescribed to the BTV. The paired student t-tests were performed. The V47.5Gy of the BTV was improved in iIMRT and VMRT compared with 3-D CRT and FiF. The mean FV doses in iIMRT and VMRT were 76.7 ± 3.9% and 85.5 ± 4.0%, respectively. However the mean ipsilateral lung doses were aggravated by iIMRT and VMRT. In terms of HYBRID, the V47.5Gy for the BTV was 97.5 ± 0.7%. The mean FV dose was 89.4 ± 2.1%. While the mean FV dose in HYBRID was 13.7 ± 2.1% (P < 0.001) lower than FiF, it was 12.8 ± 1.9% (P < 0.001) higher than iIMRT. The mean ipsilateral lung dose in HYBRID was 2.8 ± 1.9% (P < 0.001) worse than FiF, and 2.6 ± 1.8% (P < 0.001) better than iIMRT. The HYBRID could minimise the adverse dose distribution of lung and reduce 10% of the mean dose to the flapped area. For patients with adverse factors for the failure of breast reconstruction, the HYBRID could be considered.