Breast Cancer

SS 12 - Breast 1 - Toxicity

85 - Reconstruction Failure Rates in Breast Cancer Patients With Two-Stage Expander/Implant Reconstruction Receiving Regional Nodal Irradiation With VMAT: Early Results of a Phase II Trial

Monday, October 22
11:05 AM - 11:15 AM
Location: Room 214 C/D

Reconstruction Failure Rates in Breast Cancer Patients With Two-Stage Expander/Implant Reconstruction Receiving Regional Nodal Irradiation With VMAT: Early Results of a Phase II Trial
D. Gelblum1, A. Y. Ho2, Z. Cost1, B. B. Arnold3, N. Tyagi1, Z. Zhigang1, B. McCormick1, and S. N. Powell1; 1Memorial Sloan Kettering Cancer Center, New York, NY, 2Cedars Sinai, Los Angeles, CA, 3Cedars Sinai Medical Center, Los Angeles, CA

Purpose/Objective(s): Reconstruction failure (RF) is a well-known complication of radiation therapy (RT) in breast cancer patients with reconstruction. Results may vary based on RT timing and technique. We conducted a phase II trial of volumetric modulated arc therapy (VMAT) in breast cancer patients with immediate, implant-based reconstruction, hypothesizing that homogenous dose distribution to the chest wall achieved with VMAT may enhance reconstructive outcomes.

Materials/Methods: RF rates were prospectively assessed in breast cancer patients with two- stage tissue expander(TE)/permanent implant (PI) reconstruction enrolled onto an IRB-approved trial. VMAT was delivered to the chest wall and regional lymph nodes (50 Gy/25 fractions, 3mm daily bolus, no chest wall boost). The primary endpoint was RF, defined as removal of the prosthesis with or without subsequent replacement. Secondary endpoints were quality of life, cosmesis and capsular contracture rates (CC) assessed by BREAST-Q and MRI. Clinical follow-up and MRIs were performed at pre-RT, 12-18 mo and 24-30 mo post-RT. Two cohorts were identified based on RT timing: RT_PI and RT_TE. Kaplan Meier methods estimated time to RF, calculated from start of RT. Fisher’s exact and chi-squared tests compared group characteristics.

Results: 121 patients were enrolled between 5/2014 – 8/2016; 107 patients completed all study assessments and were evaluable. 48 (45%) were stage II and 59 (55%) stage III. 44 (41%) received RT_PI, 63 (59%) RT_TE. Median follow up was 26.4 mo in the entire cohort (range 9.3-43.9) and was shorter in RT_TE (25.7 vs. 28.1 mo in RT_PI). The overall 2-year RF rate was 27% (29/107), with no difference between groups (29.3% vs 23.3%, p=.37). The 2-year rate of PI removal trended higher in the RT _TE group (9.5% vs. 0% RT_PI, p=0.12). Receipt of chemotherapy, hormone therapy, smoking, diabetes and hypertension was well balanced between groups (p=NS). Median time to RF was similar (11.6 mo RT_PI vs 11.1 mo RT_TE). Etiologies for RF differed between groups: CC (9/10) and PI exposure (1/10) in the RT_PI; infection (10/19), CC (7/19), and pain (2/19) in RT_TE. Results from correlative MRI and patient-reported outcome studies and multivariate analysis will be presented.

Conclusion: In this prospective trial, the rate of RF in breast cancer patients treated with VMAT was comparable to historical patients treated with conventional, 3D-conformal RT techniques. Consistent with other published reports, one type of RT timing was not favored over another. Minimizing complications and improving patient reported outcomes remains an important goal, justifying further study of RT techniques in breast cancer patients with reconstruction.

Author Disclosure: D. Gelblum: None. A.Y. Ho: None. B.B. Arnold: None. N. Tyagi: None. B. McCormick: Stock; Varian.

Daphna Gelblum, MD, MS

Memorial Sloan Kettering Cancer Center

Disclosure:
Employment
Memorial Sloan Kettering Cancer Center: Attending Radiation Oncology: Employee

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