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Purpose: We aimed to compare breast-related complications between hypofractionated adjuvant postmastectomy radiation therapy (PMRT) and conventional fractionated radiation therapy (RT) in patients with breast cancer undergoing reconstruction by reconstruction surgery type.Methods and Materials: Data from a total of 396 patients with breast cancer who underwent breast reconstruction after mastectomy between 2009 and 2018 were retrospectively reviewed. All patients received adjuvant PMRT according to either a conventional fractionation or hypofractionation schedule. We analyzed breast-related complications according to the timing of breast reconstruction (immediate or delayed). In cases of delayed reconstruction, only PMRT delivered before final delayed reconstruction was included. A major breast complication was defined as a breast-related toxicity that required reoperation or rehospitalization after the end of RT.Results: The median follow-up time was 35.3 months (range, 8.8-122.7 months). Of all patients, 267 received immediate breast reconstruction and 129 received delayed breast reconstruction. In patients with immediate breast reconstruction, 91 were treated with conventional RT and 176 received hypofractionated RT. The occurrence of major breast-related complications did not differ significantly between the 2 fractionation regimens. Hypofractionated RT did not increase major wound problems (infection and dehiscence) compared with conventional RT. Furthermore, major contracture occurred significantly less frequently in hypofractionated RT. Of the patients who had delayed breast reconstruction, 48 received conventional RT and 81 received hypofractionated RT. There was no difference in the incidence of major breast complications between these 2 RT groups, and no difference in major breast complications were reported for either 1- or 2-stage delayed reconstruction. A time interval of >10 months between PMRT and final definitive reconstruction had a significantly lower incidence of major breast complications.Conclusions: Hypofractionated RT appears to be comparable with conventional fractionated RT in terms of breast-related complications in patients with breast cancer undergoing reconstruction, regardless of breast reconstruction type. An ongoing prospective randomized trial should confirm our findings. [ABSTRACT FROM AUTHOR]

Preclinical studies have shown that radiation therapy modulates antitumor immune responses. However, circulating T-cell responses after radiation therapy in patients with cancer have been poorly characterized. This study aims to explore the changes in circulating T cells after stereotactic body radiation therapy (SBRT). Peripheral blood samples of 30 patients with breast cancer who underwent SBRT for bone metastasis were analyzed using multicolor flow cytometry. Phenotypes of PD-1+ CD8+ T cells and regulatory T (T REG) cells were examined. Additionally, plasma protein levels were analyzed using a bead-based immunoassay. Circulating PD-1+ CD8+ T cells, which are enriched for tumor-specific clonotypes, were activated at 1 week after SBRT. However, circulating T REG cells were also activated after SBRT; this pattern was also evident among effector Foxp3hiCD45RA− T REG cells. We observed no difference in T-cell responses according to the fraction size and number. Notably, activation of T REG cells was more prominent in patients who experienced greater activation of PD-1+ CD8+ T cells. Plasma level changes in TGF-β1, soluble CTLA-4, and soluble 4-1BB at 1 week after SBRT were associated with PD-1+ CD8+ T-cell responses. Activation of T REG cells at 1 week after SBRT was associated with worse progression-free survival. Clinical factors including molecular subtype were not associated with the T-cell responses. SBRT induced activation of both potentially tumor-specific CD8+ T cells and T REG cells, which were tightly associated with each other. These results may support the use of T REG cell-modulating strategies with SBRT to improve the antitumor immune response. [ABSTRACT FROM AUTHOR]