Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Surgery

Supervisor

Turley, Eva

2nd Supervisor

Wong, Eugene

Co-Supervisor

Abstract

Radiation-induced implant capsular contracture is a challenging complication of post-mastectomy breast reconstruction. The objective of this thesis was to establish a novel rodent model that replicates the critical properties of this complication. Retired breeder female Sprague-Dawley rats underwent surgery with custom smooth silicone implants placed under the right 4th mammary fat pad. Half these rats received 26Gy of ionizing radiation to the implant and fat pad. Radiated implants had both higher Baker grades of capsular contracture and Kumar scores denoting radiation-induced fibrosis. Irradiated capsules showed increased Masson’s trichrome staining and significantly higher hydroxyproline to total protein ratio compared to controls, collectively indicating higher collagen levels in irradiated capsules. Picrosirius red staining qualitatively demonstrated a trend towards increased red birefringence in irradiated capsules, reflecting denser collagen bundling. This model is therefore a reliable reproduction of radiation-induced capsular contracture, and can be used to evaluate potential preventative and therapeutic non-surgical interventions.

Summary for Lay Audience

Breast reconstruction can improve the quality of life for women with breast cancer. Reconstructing, or creating a new breast, with silicone implants is the most common technique. Excessive scarring around the implant is a difficult problem after surgery and is greatly increased when the patient has radiation treatment. This can be extremely painful and disfiguring for the patient. This thesis outlines the creation of an animal experimental model of this scarring around implants after radiation. For the study, 13 female rats had surgery to place implants below their breast tissue on the right side. Four weeks after surgery, half of the rats then received radiation treatment to the implant and breast tissue, the other half did not. The amount of scarring around the implants was examined and graded using known rating scales. The rats were sacrificed four weeks after radiation and eight weeks after surgery. The implant with surrounding scar and breast tissue were collected. Special tests were used to look at the scarring under the microscope and also to measure the amount of collagen in the scar around the implant. The difference between the rats receiving radiation and no radiation was compared. The radiation treatment created more scarring around the implant that could be seen and felt on exam. This could also be seen under the microscope with our special stains of the scar tissue. The radiated implant scar had more collagen measured with our special test. This thesis shows successful creation of an animal model of radiation created implant scar and has potential to impact the lives of women with breast cancer. This model is special because custom miniature implants were used that are exact copies of the ones used for patients. As well, the implants were placed below breast tissue which is unique, and replicates the position in patients. This model can be used in the future to further study this scarring and test possible medications that can prevent this problem.

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