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Abstract: Radiation of the Breast: Optimization of Treatment Planning with a Gas-Filled Tissue Expander

INTRODUCTION: External beam radiation in the mantle field has been a mainstay of therapy for Hodgkin’s lymphoma for several decades. While the incidence of breast cancer in patients treated with mantle radiation is known to be elevated and mastectomy is often indicated, little has been reported regarding the outcomes of breast reconstruction in this high-risk group. The current study presents the largest series of immediate breast reconstruction in this population and aims to evaluate reconstruction outcomes and examine differences between implant-based and autologous reconstructions.


INTRODUCTION:
External beam radiation in the mantle field has been a mainstay of therapy for Hodgkin's lymphoma for several decades. While the incidence of breast cancer in patients treated with mantle radiation is known to be elevated and mastectomy is often indicated, little has been reported regarding the outcomes of breast reconstruction in this high-risk group. The current study presents the largest series of immediate breast reconstruction in this population and aims to evaluate reconstruction outcomes and examine differences between implant-based and autologous reconstructions.

METHODS:
A retrospective review of records from a 10-year period at two institutions was performed. Patients with prior mantle radiation for Hodgkin's lymphoma therapy who subsequently underwent mastectomy with immediate reconstruction were identified and included for analysis. Patient demographics, clinical characteristics, and outcomes including complications and operative revisions were collected. Univariate and multivariate analyses were performed to examine differences between implant-based and autologous reconstructions.

RESULTS:
A total of 99 breast reconstructions were performed in 53 patients. 81 reconstructions were implant-based and 18 were autologous. Patients with autologous reconstructions were younger than implant-based reconstructions (42 ± 6.5 vs 47 ± 8.8 years, p<0.05), otherwise, the groups were similar with respect to BMI, medical comorbidities, oncologic diagnosis, and therapy. The time between mantle radiation and reconstruction was similar for implant-based and autologous groups (23.4 ± 9 vs 21.3 ± 6.1 years, p=0.6). The overall breast complication rate was not statistically different between the implant-based and autologous groups (35% vs 16%, p=0.16). Three implant-based reconstructions (3.7%) failed requiring explantation, and there were no complete flap losses in the autologous group. Autologous reconstruction group was associated with over 5-fold higher rate of unplanned revisions compared to the implant-based reconstruction group (OR: 5.29, 95% CI: 1.24-22.51, p=0.025).
CONCLUSION: Immediate breast reconstruction in patients with prior mantle radiation can be achieved safely with an acceptable complication profile utilizing both implant-based and autologous techniques. Autologous breast reconstruction is associated with higher rate of revisions compared to implant-based breast reconstruction.

Presenter: Yvonne Zissiadis, MBBS, FRANZCR; Affiliation: Genesis Cancer Care, Wembley
INTRODUCTION: Radiation of the breast with a saline tissue expander in situ has been managed successfully for many years despite the presence of an embedded metallic injection port. A new breast tissue expander has been introduced that is filled with carbon dioxide released via remote control from a stainless-steel reservoir located within PSTM 2017 Abstract Supplement Saturday, October 7, 2017 the expander. Radiation oncologists and medical physicists will need to consider what effect the gas filled chamber and metal components within the expander have on their treatment planning and dosimetry. Breast air expanders require a wedged pair planning technique however, Saline expanders can be planned with a IMRT hybrid technique. It is critical to understand the contour and overrides to get an accurate dose distribution in pinnacle.

METHODS:
All patients referred for radiation therapy with the AeroForm Tissue Expander in place were evaluated at the Genesis Cancer Care in Western Australia. Treatment planning was conducted after evaluation of the device properties. The Radiation Oncologist marks the clinical target volume (skin, subcutaneous tissue), a planning target volume is then created (beam generated ptv).

RESULTS:
Patients referred to the radiation oncology team with the AeroForm Tissue Expander in place underwent routine CT guided treatment planning. Treatment plans were implemented with consideration of the density and position of the stainless-steel reservoir as well as the potential effects of radiation through an air-filled chamber. Details of the planning technique are included. A total of 9 patients with Aeroform Tissue Expanders in situ have been treated with chest wall Radiation Therapy for local control. All patients were able to complete their course of radiation without noticeable effect of the AeroForm Tissue Expander on acute toxicity.

CONCLUSIONS:
CT based optimization of dosimetry with respect to the properties of the new gas-based expander was completed to successfully reduce dose variation in patients with the gas-filled expander in place. When patients are referred for breast radiation therapy, it is important to inform the radiation oncologist of the presence of this expander for optimal treatment planning.