Effect of internal port on dose distribution in post-mastectomy radiotherapy for breast cancer patients after expander breast reconstruction

Background: In patients with expander-based reconstruction a few dosimetric analyses detected radiation therapy dose perturbation due to the internal port of an expander, potentially leading to toxicity or loss of local control. This study aimed at adding data on this field. Materials and methods: A dosimetric analysis was conducted in 30 chest wall treatment planning without and with correc-tion for port artifact. In plans with artifact correction density was overwritten as 1 g/cm3. Medium, minimum and maximum chest wall doses were compared in the two plans. Both plans, with and without correction, were compared on an anthropo-morphic phantom with a tissue expander on the chest covered by a bolus simulating the skin. Ex vivo dosimetry was carried out on the phantom and in vivo dosimetry in three patients by using film strips during one treatment fraction. Estimated doses and measured film doses were compared.Results: No significant differences emerged in the minimum, medium and maximum doses in the two plans, without and with correction for port artifacts. Ex vivo and in vivo analyses showed a good correspondence between detected and calculated doses without and with correction.Conclusions: The port did not significantly affect dose distribution in patients who will receive post-mastectomy radiation therapy.