Abstract PS15-17: Hypofractionated versus conventional intensity modulated postmastectomy radiotherapy: Toxicity and quality of life in patients with tissue-expander breast reconstruction
Authors: Fariña Ariel , Alfonso Dagmar , Fernandez Aroldo , Carvajal Felipe , Ciudad Ana María , Martínez Celmira , Pérez Camila , González Pablo , Marsiglia Hugo 
Published: February 2021

Abstract
Introduction: Hypofractionation (HF) in breast cancer is a radiotherapy regimen frequently used in recent years. Greater toxicity has been described in irradiated patients with heterologous breast reconstruction procedures, but it is unknown if this greater toxicity could be avoided by using hypofractionated intensity modulated radiotherapy (IMRT). The objective of this study is to describe the toxicity and complications presented in breast cancer patients that were reconstructed with a tissue expander (EXP) treated with IMRT and to determine if there are differences according to the used fractionation regimen.
Method: All patients with breast cancer reconstructed with expander and treated with adjuvant IMRT to the chest wall and regional lymph nodes were included, using conventional fractionation (CF) dose of 50 Gy in 25 fractions or hypofractionated (HF) regimen dose of 45 Gy in 20 fractions. Acute and late toxicity, during treatment and at the end of follow-up, were recorded according to RTOG / EORTC and CTCAE 4.0 criteria and the BREAST Q 2.0 quality of life survey postoperative reconstruction module (QoL) was applied in the last follow-up visit.
Results: 33 patients were analyzed. With a median follow-up of 17 months, 31 were treated with Tomotherapy and 2 with VMAT. CF was used in 20 and HF in 13. There was no G3 acute toxicity, and G2 was observed in only 1 patient with HF (7.6%) and in 3 with CF (15%), mainly determined by radiodermatitis. Regarding late toxicity (LT), there was only one G3 event which occurred in a patient with CF and full axillary irradiation. Grade 2 LT was not observed in patients treated with HF, whereas with CF 2 cases (10%) were reported. During the expander period, 1 patient with HF presented a complication (7,6%) and 3 with CF (15%), 2 of the latter required unscheduled surgical intervention (USI). 12 patients in the HF group underwent prosthetic replacement (92%) and 15 in the CF group (75%). After the replacement 4 patients with CF required an USI (26.6%) and none of the patients in the HF group had post replacement complications that required hospitalization. None of the previously mentioned differences were statistically significant. Regarding QoL, the patients with HF had a better late toxicity score, with an average of 96.7 vs. 82.4 points (p &lt;0.005), and better physical well-being of the chest, with an average of 81.7 vs. 66 points, which did not reach statistical significance (p = 0.052). The rest of the scales within the module did not show any differences. Conclusions: Postmastectomy IMRT in patients with heterologous reconstruction is associated with low toxicity and complications. The use of hypofractionation presents a toxicity profile similar to that of conventional fractionation, with a tendency to less frequent complications associated with reconstruction. HF is also associated with a better QoL score in late toxicity and physical well-being of the chest. Prospective studies are required to confirm whether hypofractionation using IMRT could decrease complications and improve quality of life in patients undergoing total mastectomy and tissue-expander breast reconstruction.
Citation Format: Ariel Fariña, Dagmar Alfonso, Aroldo Fernandez, Felipe Carvajal, Ana María Ciudad, Celmira Martínez, Camila Pérez, Pablo González, Hugo Marsiglia. Hypofractionated versus conventional intensity modulated postmastectomy radiotherapy: Toxicity and quality of life in patients with tissue-expander breast reconstruction [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-17.