Abstract P3-13-11: The outcomes of ReFilx soft tissue filler as an immediate reconstruction technique for lumpectomy followed by radiotherapy

Abstract

Abstract Introduction: Lumpectomy for breast cancer can often result in poor cosmetic outcomes which can lead to long-lasting impairment of quality of life. ReFilx is a synthetic porous degradable polyurethane scaffold that has mechanical properties comparable to that of native healthy breast tissue. It has been shown in two previous porcine studies to preserve breast shape and volume over 9 months when inserted into the cavities immediately after lumpectomy. We observed minimal foreign body reaction with good integration of the host tissue while the material degraded over time. In this study, we examined the healing process of lumpectomy treated with radiation. Radiotherapy is currently a standard adjuvant therapy after lumpectomy for breast cancers; and radiation is known to affect the healing process in general. Objective: To evaluate ReFilx, as soft tissue fillers for lumpectomy cavities in combination with standard radiotherapy. Hypothesis: ReFilx will preserve breast shape and volume by supporting tissue infiltration with minimal inflammation in the presence of clinically relevant radiotherapy. Methods: 3 female Yucatan minipigs received lumpectomies carried out using electrocautery to remove normal breast tissue of approximately 2 cm diameter, after which the cavities were filled with (case) or without ReFilx (sham control) (n=3 for each condition, each pig has 12-13 breasts). 6 weeks post-implantation, 2 of the pigs received radiation directed at the right half of their bodies (6 breasts per pig) for a total dose of 42.4 Gy delivered over 15 fractions using a clinical linear accelerator. The delivered doses to target sites and the adjacent tissue were confirmed with optically stimulated luminescent dosimeters (OSLDs). A third pig was maintained as a non-irradiated control. Ultrasound examinations were performed every 3 weeks post-implantation. At week 24 and 36, samples consisted of n=3 for irradiated and non-irradiated ReFilx and sham sites for the half-irradiated pigs, and n=3 for non-irradiated ReFilx and sham sites for the non-irradiated control pig were excised by mastecomy, the tissue samples were fixed in 10% buffered formalin for subsequent histological (H&E, Masson's Trichrome) studies. Potential side effects were monitored by vital signs, pain control, wound checks, ultrasound and blood tests. Necropsies were performed at the conclusion of the study. Results: Ultrasound examination indicated no difference between ReFilx's ability to maintain breast shape and volume with or without the presence of radiation treatment, in contrast to the collapse of the sham sites by 24 weeks. Similarly, the histology of irradiated and non-irradiated ReFilx samples showed similar levels of tissue infiltration, inflammatory changes and degradation of ReFilx. There was no significant side effects observed. Conclusions: ReFilx's ability to act as a soft tissue filler for breast volume restoration post-lumpectomy does not appear to be significantly impacted by the presence of clinically relevant radiation treatment. Longer-term follow-up is currently in progress for this study. Acknowledgements: Connaught Innovation Award (University of Toronto) and Joule Innovation Fund (Canadian Medical Association). Citation Format: Leong WL, Battiston K, Cheung F, Fulton C, Lin A, Levin W, Done S, Santerre P. The outcomes of ReFilx soft tissue filler as an immediate reconstruction technique for lumpectomy followed by radiotherapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-13-11.