Initial clinical experience of postmastectomy intensity modulated proton therapy in patients with breast expanders with metallic ports.
OBJECTIVE
The feasibility of proton postmastectomy radiation therapy in patients reconstructed with expanders has not been previously reported, limiting treatment options. We analyzed the dosimetric impact of the metallic port contained within expanders on intensity modulated proton therapy (IMPT) and report our techniques and quality control for treating patients in this setting.


METHODS
Twelve patients with the same expander model underwent 2-field IMPT as part of a prospective registry. All planning dosimetry was checked with an in-house graphic processing unit--based Monte Carlo simulation. Proton ranges through the expander were validated using a sample implant. Dosimetric impact of setup metallic port position uncertainty was evaluated. Pre- and posttreatment photographs were obtained and acute toxicity was graded using the Common Terminology Criteria for Adverse Events, version 4.0.


RESULTS
Nine patients had bilateral skin-sparing mastectomy with bilateral tissue expander reconstruction, and 3 patients had unilateral skin-sparing mastectomy and reconstruction. The left side was treated in 10 patients and the right side in 2. Target coverage and normal tissue dose uncertainties resulting from the expander were small and clinically acceptable. The maximum physician-assessed acute radiation dermatitis was grade 3 in 1 patient, grade 2 in 5 patients, and grade 1 in 6 patients.


CONCLUSIONS
Postmastectomy IMPT in breast cancer patients with expanders is feasible and associated with favorable clinical target volume coverage and normal tissue sparing, even when taking into account treatment uncertainties; therefore, these patients should be eligible to participate in clinical trials studying the potential role of proton therapy in breast cancer. We caution, however, that institutions should carry out similar analyses of the physical properties and dosimetric impact of the particular expanders used in their practice before considering IMPT.
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota. Electronic address: mutter.robert@mayo.edu.
Robert W
RW
Mutter
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Nicholas B
NB
Remmes
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Mohamed Mh
MM
Kahila
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Kathy A
KA
Hoeft
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Deanna H
DH
Pafundi
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Yan
Y
Zhang
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Kimberly S
KS
Corbin
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Sean S
SS
Park
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Elizabeth S
ES
Yan
Division of Plastic and Reconstructive Surgery, Mayo Clinic, Rochester, Minnesota.
Valerie
V
Lemaine
Department of Surgery, Mayo Clinic, Rochester, Minnesota.
Judy C
JC
Boughey
Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
Chris J
CJ
Beltran
D000328:Adult; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008408:Mastectomy / Q000379:methods*; D008875:Middle Aged; D061766:Proton Therapy / Q000379:methods*; D015625:Tissue Expansion Devices