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The impact of prepectoral implant positioning in breast reconstruction on the technical delivery of postmastectomy radiotherapy
Deutschmann C.1, Knoth J.1, Gschwantler-Kaulich D.1, Singer C.F.1, Leser C.1, Kauer-Dorner D.1
1Medizinische Universität Wien, Wien, Österreich

Background: Concerning the impact of implant-based breast reconstruction (IBBR) on the technical delivery of postmastectomy radiation therapy (PMRT) data is limited particularly lacking studies on the effect of prepectoral implant positioning on postmastectomy radiation planning.
Methods: A retrospective chart review and reevaluation of CT planning scans of all patients who received a PMRT following an IBBR between 2013 and 2018 at the University Clinic of Radiotherapy of the Medical University of Vienna, Austria was performed.
Results and discussion: In total 10 patients (10 breasts, 3 right-sided, 7 left-sided) with prepectoral implants and 12 patients (13 breasts, 7 right-sided, 6 left-sided) with retropectoral implants were included in the study.
No major compromises in defining the clinical target volume (CTV) or planning target volume (PTV) due to the implant position were noted.
Regarding dosimetric characteristics of the PTV a statistically significant difference in PTV D90 (%) (p =.006) and PTV Dmax(%) (p = .046) with higher values in the prepectoral compared to the retropectoral cohort was found.
Regarding dosimetric characteristics of organs at risk (OAR) a statistically significant difference in Lung Dmax(%) (p = .027) and Lung Dmean(%) (p = .039), with higher values being present in the prepectoral compared to the retropectoral cohort were found.
Any differences in dosimetric characteristics of the PTV and OAR could be explained by the higher percentage of new radiation techniques in the prepectoral cohort.