Do metallic ports in tissue expanders affect postmastectomy radiation delivery?

PURPOSE: Postmastectomy radiation therapy (PMRT) is often delivered to patients with permanent breast implants. On occasion, patients are irradiated with a tissue expander (TE) in place before their permanent implant exchange. Because of concern of potential under-dosing in these patients, we examined the dosimetric effects of the Magna-Site (Santa Barbara, CA) metallic port that is present in certain TEs. METHODS AND MATERIALS: We performed ex vivo film dosimetry with single 6-MV and 15-MV photon beams on a water phantom containing a Magna-Site disc in two orientations. Additionally, using in vivo films, we measured the exit dose from 1 patient's TE-reconstructed breast during chest wall treatment with 15-MV tangent beams. Finally, we placed thermoluminescent dosimeters (TLDs) on 6 patients with TEs who received PMRT delivered with 15-MV tangent beams. RESULTS: Phantom film dosimetry revealed decreased transmission in the region of the Magna-Site, particularly with the magnet in the parallel orientation (at 22 mm: 78% transmission with 6 MV, 84% transmission with 15 MV). The transmission measured by in vivo films during single beam treatment concurred with ex vivo results. TLD data showed acceptable variation in median dose to the skin (86-101% prescription dose). CONCLUSION: Because of potential dosimetric effects of the Magna-Site, it is preferable to treat PMRT patients with permanent implants. However, it is not unreasonable to treat with a TE because the volume of tissue affected by attenuation from the Magna-Site is small. In this scenario, we recommend using 15 MV photons with compensating bolus.

Unilateral postoperative chest wall radiotherapy in bilateral tissue expander/implant reconstruction patients: a prospective outcomes analysis.

BACKGROUND: Implant reconstruction has a major role to play in breast reconstruction, as some patients neither wish nor are suitable for autogenous reconstruction. The suitability of implant reconstruction in patients who may receive postoperative, adjuvant radiation therapy has not, however, been fully clarified. The purpose of this study was to evaluate complications, capsular contracture, aesthetic outcomes, and patient satisfaction in patients who have undergone bilateral tissue expander/implant reconstruction and unilateral, post exchange, adjuvant radiotherapy. In this study population, the effect of radiation can best be appreciated because the nonirradiated breast acts as a control. METHODS: A review of all bilateral tissue expander/implant reconstructions at a single cancer center was undertaken. Twelve patients who underwent bilateral expander/implant reconstruction and unilateral postexchange radiotherapy were eligible for participation. A prospective evaluation of complications, cosmesis, and patient satisfaction was performed. The evaluation of cosmesis and patient satisfaction was executed for 10 of the 12 patients, as two were dead at the time of follow-up. RESULTS: Mean follow-up was 23.5 months (range, 12 to 58.5 years). In 40 percent of patients, there was no discernible difference in capsular contracture between the irradiated and nonirradiated breasts. In 50 percent of patients, the irradiated breast demonstrated increased contracture by a single modified Baker grade. In 10 percent of patients, contracture of the irradiated breast was two modified Baker grades greater than that of the nonirradiated side (grade III versus grade I). CONCLUSION: For the majority of patients, the degree of capsular contracture was higher on the irradiated side, yet overall symmetry, aesthetic results, and patient satisfaction remained high. These data support the conclusion that immediate, bilateral breast reconstruction using tissue expansion and implants is an acceptable option for the subset of patients who may undergo unilateral, postexchange radiotherapy.