ESTRO 2024 - Abstract Book

S491

Clinical - Breast

ESTRO 2024

Capsular contracture is a significant challenge faced by breast cancer patients who undergo post-mastectomy radiotherapy (PMRT) after implant-based breast reconstruction (IBR). A wide range (16.9% to 67.5%) of incidence of capsular contracture following PMRT with implant-based reconstruction has been reported [1-3]. There is no specific treatment to directly treat or manage capsular contracture, underscoring the importance of its prevention. Our study aims to identify the risk factors and dosimetry characteristics associated with capsular contracture.

Material/Methods:

We performed a retrospective analysis of patients who underwent PMRT following an IBR between 2010 and 2022. Capsular contracture was categorized in Baker-Classification for Reconstructed Breasts. The primary outcome comprised the occurrence of capsular contracture and reconstruction failure. Possible risk factors included patient characteristics, tumor classifications, chemotherapy, hormone therapy, postoperative complications (prolonged pain, seroma, prolonged wound healing), radiation extent, technique and dosimetry and were analyzed using Chi square test or Wilcoxon rank sum test. Kaplan-Meier method was used to visualize the differences between the assumed risk factors. Patients were censored either at the first diagnosis of capsular contracture, death or at the last follow-up, measured in months starting the last day of radiotherapy. A p-value<0.05 was considered to be significant.

Results:

118 breast cancer patients who received PMRT (50.0-50.4 Gy in 25-28 fractions) following IBR were identified. After a median follow-up of 22 months, the incidence of clinically relevant capsular contracture (Baker III-IV) was 22.9%. Overall, capsular contracture (Baker I-IV) occurred on 56 patients (47.5%) in a median of 9 months (IQR: 3.0-16.5 months) after PMRT. Of 56 patients with capsular contracture, 4 patients (7.1%) were classified as Baker I, with 25 (44.6%), 14 (25.0%) and 13 (23.2%) patients categorized as Baker II, III and IV respectively (Figure 1). The rate of reconstruction failure/implant loss was 25.4%. Eighty-one patients (68.6%) were irradiated using DIBH and 37 patients (31.4%) in free-breathing, 102 patients (86.4%) were treated using VMAT, meanwhile 16 patients (13.5%) in 3D-CRT. 5 patients (4.2%) received additional boost dose. Postoperative complications (prolonged pain, prolonged wound healing, seroma and swelling) were associated with higher rate of capsular contracture (p=0.017, OR: 2.5 95%CI: 1.2-5.3). We observed a higher rate of capsular contracture on patients who received chemotherapy, although insignificant (p=0.153). We found no significant association between its occurrence with age, menopausal status, BMI, hormone therapy and admission of Her2-targeted therapy. Interestingly, a higher nodal status was associated with an increased incidence of capsular fibrosis (p=0.031). Detailed dosimetric analysis of radiotherapy (Table 1) did not reveal any significant correlation with the occurrence of capsular contracture. Furthermore, the extent of nodal irradiation (p=0.183) as well as the admission of boost-irradiation (p=0.580) was not significantly associated with capsular contracture. Multivariate analysis revealed postoperative complications and nodal status as independent prognostic factors for the occurrence of capsular contracture (p<0.001 and p=0.025 respectively).