FAQs - Radiation Therapy

Images courtesy of Martin Keisch, MD
University of Miami

Can a patient continue expanding while undergoing radiation treatments?
Active expansion should not be done during the time the patient is undergoing radiation treatments. It is important that the volume of the Expander remain constant once the CT-planning is completed and until radiation treatment is completed.
Does radiation impact the function of an implanted AeroForm Expander?
Functional testing was conducted and concluded that the electronics inside the Expander continue to function properly after exposure to radiation levels up to 75 Gy, which is well above the maximum total dose level typically used in post-mastectomy radiation therapy (50Gy)(Rembert J. et al.).
How does the position of the Expander impact radiation planning?
Expanders may be placed in a sub-pectoral or pre-pectoral position.

In most cases, the anterior surface of the pectoral muscle is the anatomic deep border to cancer risk. Thus, in the sub-pectoral position, the target area is anterior to the Expander. However, in the pre-pectoral position, the target area is surrounding and underneath the Expander.
What if the Radiation Oncologists requires deflation of the contralateral side?
The AeroForm Expander cannot be deflated. Deflation of the contralateral side for radiation treatment is not typically necessary with the state of the art algorithms that allow the radiation oncologist to contour the beam and avoid adjacent structures.

If the radiation oncologist requires that the Expander on the contralateral side be in a deflated state, it may be best to delay full expansion on that side until the radiation treatment is completed. This assessment can be determined prior to full inflation with a mock CT simulation if it is a potential concern.
What are factors to consider when radiation is delivered with the AeroForm Expander in place versus a saline expander?
  • The Expander is filled with gas (CO2) instead of liquid - which may theoretically impact dose planning - since the radiation x-ray beam travels through a gas medium easier than through liquid or tissue.
  • There is an internal metal reservoir. This stainless steel reservoir is affixed to the posterior wall - away from the skin surface. Compared to a saline expander, whose metal component (magnetic port) is located on the anterior wall of the Expander - closer to the skin surface.
  • The AeroForm reservoir is not uniformly dense; there are 3 distinct sections.
What peer-reviewed studies have been published studying radiation of the breast with the AeroForm Expander?
What peer-reviewed studies have been published studying radiation of the breast with the AeroForm Expander?

Moni J. et al., Dosimetric Impact of the AeroForm Tissue Expander in post-mastectomy radiation therapy – An ex vivo analysis
(Practical Radiation Oncology April 2015)

Purpose: The study was designed to evaluate the effect of the AeroForm Expander on dose distribution in a simulated postmastectomy radiation treatment.

Conclusion: Film dosimetry demonstrated beam attenuation in the shadow of the metallic reservoir in the Expander. This decrease in dose was not reproduced on the intact Expander on the phantom designed to replicate a clinical setup. There was very little difference in the measured vs expected dose.

Tran, T. et al., A dosimetric analysis of the aeroform™ tissue expander in radiation therapy (Int J Cancer Ther Oncol 2014; 2(3):020316. DOI: 10.14319/ijcto.0203.16)

Purpose: The aim of this study is to evaluate the effects of the metallic reservoir and the use of gas within the AeroForm™ tissue expander with respect to the radiation dose distribution.

Conclusion: Dosimetric effects due to the metallic reservoir within the AeroForm breast tissue expander have been demonstrated and have been observed to be significant. To increase the dosimetric accuracy when contouring, individual components of the reservoir should be distinguished. Our in-vivo experiment showed that dose homogeneity was difficult due to the metallic reservoir and we recommend stringent patient dose monitoring when using this expander during radiotherapy.

Kuo JV et al. Dose Measurements in the post-mastectomy irradiation of a patient with a gas based tissue Expander (ASTRO Meeting 2013)

Purpose: This study was designed to investigate the dosimetric consequences of the Expander’s, gas-filled compartment within the treatment volume.

Conclusion: The dosimetric realities of treating a tumor within a gas (i.e. most lung cancers) or accommodating a metallic object within/adjacent to a radiated volume (i.e. hip replacements) are not unique and are encountered by radiation oncologists frequently. Radiation oncologists should follow their standard practice when dealing with these issues: utilizing low energy photon beams (~6MVx) for improved dose build-up at the gas/tumor interface, utilizing dose heterogeneity corrections with a state-of-the art dose calculation algorithm (AAA, Monte Carlo etc). In addition, treating physicians may want to perform in vivo dose measurements to ensure that the expected skin dose is being delivered.

Rembert J. et al., Radiation Testing of the AeroForm CO2-based breast tissue Expander implant (Radiation Oncology 2013 8:235)

Purpose: This study was designed to evaluate the impact of radiation levels up to 75 Gy on AeroForm® Tissue Expanders and on the associated internal printed assemblies. (Breast cancer patients who undergo mastectomy and tissue expander/implant-based breast reconstruction may require radiation therapy at doses up to 50-60 Gy while the Expander is in place.)

Conclusion: The electronics inside the AeroForm Tissue Expander implant continued to function properly after exposure to radiation levels up to 75 Gy, which is well above the maximum total dose level typically used in post-mastectomy radiation therapy. Standard post-mastectomy radiation therapy doses do not damage or affect the functionality of the AeroForm Tissue Expander.
Images courtesy of Martin Keisch, MD
University of Miami