Breast Cancer

PV 01 - Poster Viewing Q&A - Session 1

SU_12_2111 - Capsular Contracture after Radiation Therapy Following Mastectomy and Implant-Based Reconstruction

Sunday, September 15
1:15 PM - 2:30 PM
Location: ASTRO Innovation Hub

Capsular Contracture after Radiation Therapy Following Mastectomy and Implant-Based Reconstruction
J. Anderson1, J. B. Hammond2, C. S. Thorpe1, H. E. Kosiorek3, B. A. Pockaj4, R. J. Gray2, P. A. Cronin2, A. M. Rebecca5, W. J. Casey5, W. W. Wong6, S. R. Keole6, T. Z. Vern-Gross7, L. A. McGee1, M. Y. Halyard1, and C. E. Vargas8; 1Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 2Department of General Surgery, Mayo Clinic, Phoenix, AZ, 3Department of Research Biostatistics, Mayo Clinic, Phoenix, AZ, 4Department of Surgery, Mayo Clinic, Phoenix, AZ, 5Department of Plastic Surgery, Mayo Clinic, Phoenix, AZ, 6Mayo Clinic Arizona, Phoenix, AZ, 7Mayo Clinic, Phoenix, AZ, 8Mayo Clinic, Scottsdale, AZ

Purpose/Objective(s): Radiation therapy (RT) is a known risk factor for capsular contracture (CC) in breast cancer patients undergoing mastectomy and implant-based reconstruction, and there is relatively little data in the literature exploring radiation related details associated with risk of CC. We hypothesize that radiation specific details may be associated with increased risk of CC.

Materials/Methods: From 2010-2017, 53 patients underwent RT following mastectomy with implant-based reconstruction for invasive cancer or local recurrence at a single institution. Patients were treated with photon therapy using opposed tangents (n=45) or VMAT (n=2); and proton therapy (n=6). Radiation boost (n=27), when delivered, consisted of electrons to the surgical scar. CC was diagnosed based on physical exam findings. Patient and radiation specific risks for CC were analyzed using chi-square test for frequency data and Wilcoxon rank-sum test for continuous data.

Results: Median follow-up was 17.6 months (range 0.03 – 79.5 months). CC occurred in 10 out of 53 (18.9%) patients. Surgical reconstruction was evenly split between stage I (50.9%) and stage II (49.1%) with no difference in risk of CC (p=0.18). The majority of patients received 50 Gy in 25 fractions (70%) to the whole breast. Radiation doses ranged from 40.05 Gy in 15 fractions to 56.7 Gy in 28 fractions. Body mass index (BMI) did not differ between patients with CC (median=23.7, range 19.2-30.57) compared to those without CC (median=24.1, range 17.1-39.0, p=0.55). Breast volume treated did not differ between patients with CC (median=885.1 cm3, range 435.1-1798) compared to those without CC (median=773.9 cm3, range 103.8-1423.2, p=0.57). All patients who developed CC in our population received a minimum 50 Gy in 25 fractions. Hypofractionation was used in 5 patients and none of them developed CC (p=0.57). CC occurred in 2 of 6 patients (33%) who received proton therapy compared to 8 of 47 (17%) who received photon therapy (p=0.31). Boost to the surgical scar was not associated with an increased risk of CC (p=0.72). CC occurred in 9 of 32 patients (28.1%) who received neoadjuvant chemotherapy compared to 1 of 21 (4.8%) patients who did not receive neoadjuvant chemotherapy (p=0.07).

Conclusion: Hypofractionation was not associated with a higher risk of CC compared to standard fractionation. BMI and volume of breast tissue treated were not associated with risk of CC either. Patients treated with neoadjuvant chemotherapy in addition to RT following mastectomy and implant-based reconstruction may be at increased risk for CC.

Author Disclosure: J. Anderson: None. J.B. Hammond: None. H.E. Kosiorek: None. R.J. Gray: None. W.J. Casey: None. T.Z. Vern-Gross: None. M. Halyard: Vice Dean Mayo Medical School; Mayo Clinic College of Medicine and Science. C.E. Vargas: Chairman; Proton Collaborative Group. Stock; View Ray.

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