Breast Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_2_3341 - Early toxicity and patient reported outcomes of post-mastectomy pencil-beam scanning proton therapy in women with immediate tissue expander breast reconstruction

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Early toxicity and patient reported outcomes of post-mastectomy pencil-beam scanning proton therapy in women with immediate tissue expander breast reconstruction
N. Smith1, K. R. Jethwa1, K. Gonuguntla1, S. Elswick2, J. Grauberger3, A. Amundson1, T. J. Whitaker1, N. Remmes1, C. Harless2, J. C. Boughey4, S. S. Park1, V. Lemaine2, E. S. Yan1, K. S. Corbin1, and R. W. Mutter1; 1Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 2Department of Plastic Surgery, Mayo Clinic, Rochester, MN, 3Mayo Clinic School of Medicine, Rochester, MN, 4Department of Breast Surgery, Mayo Clinic, Rochester, MN

Purpose/Objective(s): We previously reported the feasibility of intensity modulated proton postmastectomy radiotherapy (P-PMRT) in women with immediate tissue expander (TE) reconstruction with metallic ports. Our purpose is to analyze early complication rates and patient reported outcomes of this novel treatment approach.

Materials/Methods: All patients underwent mastectomy, axillary staging, and immediate TE placement. P-PMRT was delivered to the chest wall and regional lymphatics, including the internal mammary nodes, to a median dose of 50 Gy (RBE1.1) in 25 fractions with a median of two multifield optimized beams. Second-stage implant or autologous reconstruction took place a minimum of 6 months after the completion of P-PMRT. Adverse effects, patient-reported quality of life (QoL), and breast cosmesis were prospectively-assessed with the CTCAEv4.0, linear analog 10-point scales, and the Harvard Breast Cosmesis Scale, respectively.

Results: Between 2015 and 2017, 53 patients underwent mastectomy with immediate TE reconstruction followed by P-PMRT. TE placement was prepectoral in 40 (75%) and subpectoral in 13 (25%). Forty patients (75%) underwent contralateral prophylactic mastectomy with TE reconstruction. Median age was 49 (interquartile range [IQR] 43-57). The tumor was left-sided in 36 (68%), right-sided in 14 (26%), and bilateral in 3 (6%). Chemotherapy [neoadjuvantly (68%) or adjuvantly (15%)] was delivered in 44 (83%) patients, prior to P-PMRT. Median time from surgery to initiation of P-PMRT in the 45 patients who did not receive adjuvant chemotherapy was 59 days (IQR 53 - 71). The median mean heart dose and ipsilateral lung V20 Gy was 0.65 Gy (IQR 0.44 - 0.92) and 13.9 % (IQR 10.3% - 15.3%), respectively. Maximal acute dermatitis grade was 1 in 60%, 2 in 26%, and 3 in 8%. Median follow-up after P-PMRT was 8 months. Six of 56 (11%) irradiated and 1 (3%) non-irradiated implants had been removed due to complications. Other reconstruction complications are shown in the table. QoL was reported as ≥7 in 75% at baseline prior to P-PMRT initiation, with improvement to 83% at 6-months post-treatment. Eighty-six percent of responding patients reported good or excellent cosmesis at 6-month follow-up.

Conclusion: Early toxicity and patient reported outcomes of P-PMRT appear favorable in patients with immediate TE reconstruction, although complications remain higher on irradiated vs non-irradiated sides. Intensity modulated P-PMRT is a promising cardiopulmonary sparing modality for women with immediate reconstruction. Table:
Complications Irradiated, n = 53 Non-irradiated, n= 43
Total 19 (36%) 2 (5%)
Infection Prior to P-PMPT 2 (4%) 2 (5%)
<30 days after completion of P-PMPT 2 (4%) 0
>30 days of P-PMPT to second stage procedure 7 (13%) 0
After second stage procedure 4 (8%) 0
Implant removal 6 (11%) 1 (2%)
Seroma 4 (8%) 0
Mastectomy skin flap necrosis 2 (4%) 0
Capsular contracture 1 (2%) 0

Author Disclosure: N. Smith: None. K.R. Jethwa: None. K. Gonuguntla: None. S. Elswick: None. N. Remmes: None. J.C. Boughey: Research Grant; NCI. Publications Committee Chair; ASBS. E.S. Yan: Research Grant; Canadian Institutes of Health Research. Travel Expenses; Netcare Healthcare. Reviewer; Canadian Institutes of Health Research. Committe Member; ACTION. R.W. Mutter: Research Grant; ASTRO.

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