Abstract P2-12-15: ReFilx- synthetic biodegradable soft tissue fillers for breast conserving surgery in breast cancer
Authors: Leong WL , Sharifpoor S , Battiston K , Charleton D , Corrigan M , McCready DR , Done SJ , Santerre JP 
Published: February 2018

Abstract
Introduction: Breast conserving surgery (BCS) is the most common procedure performed in breast cancers, but it can often result in breast deformities that can have negative impacts on quality of life. With better treatments, more breast cancer survivors are expected to live longer, the demand for achieving optimal cosmetic outcomes has also increased accordingly. Currently, oncoplastic techniques involving local tissue rearrangement with or without contralateral balancing procedures are used in specialized centers to achieve breast symmetry in some patients. When a breast deformity occurs, corrective options include: fat grafting, autologous flap procedures and completion mastectomy with immediate reconstruction. These techniques have long operative times, longer length of hospital stay and higher complication rates. Commercially-available synthetic implants are fabricated in pre-determined sizes and thus are not suitable to reconstruct partial breast deformities of varying size and shape. We explored the use of amino-acid based biodegradable polyurethanes as tissue fillers for BCS due to their chemical versatility, superior mechanical properties and tailored biocompatibility. Objective: To evaluate novel biodegradable polymer constructs, referred to as ReFilx, as soft tissue fillers for BCS defects. Hypothesis: Implantation of ReFilx during BCS will maintain breast shape and size and promote tissue regeneration in and around the biodegradable biomaterial, in contrast to sham controls. Methods: Two ReFilx formulations with high porosity, mechanical properties (compressive modulus=45±6 kPa and 31±9 kPa) comparable to native breast tissue and a moderate degree of swelling (202±6% and 248±6%) were selected for implantation in porcine BCS defects. Three female Yucatan Minipigs (age=4 years, weight=100-120 kg, 12 breasts per pig) received BCS to remove normal breast tissue of approximately 2 cm diameter, after which the defects were filled with ReFilx Formulation A, ReFilx Formulation B, or no filler (sham control). At 6, 12, 24, and 36 weeks post-implantation (n=3 per group), ultrasound breast examinations and mastectomies of each selected group of breasts were performed. Samples were fixed in 10% buffered formalin and stained with H&E, Masson's Trichrome and immunohistomchemistry using CD31. Results: ReFilx formulations maintained breast size and shape, with similar stiffness to native breast tissue, while sham controls collapsed over 36 weeks. The ReFilx fillers supported cell and tissue infiltration and neovascularization, as indicated by Masson's Trichrome and CD31 staining, respectively, without eliciting foreign body giant cell formation, fibrosis, or chronic inflammation, commonly associated with implanted medical devices. Conclusions: ReFilx are promising soft tissue fillers for breast volume restoration, representing a simple, versatile, permanent, and aesthetically superior solution to prevent soft tissue deformities. Acknowledgements: MaRS PoP fund, grant # MI 2011-170, NSERC # SYN 430828. Haynes Connell Foundation Breast Cancer Fund.
Citation Format: Leong WL, Sharifpoor S, Battiston K, Charleton D, Corrigan M, McCready DR, Done SJ, Santerre JP. ReFilx- synthetic biodegradable soft tissue fillers for breast conserving surgery in breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-12-15.