A patient who had undergone placement of a temporary tissue expander immediately following modified radical mastec┬Čtomy, was evaluated for receiving external beam radiation therapy to the breast mound. Due to the presence of a 6.3 cm tumor as well as involvement of 8 axillary lymph nodes, this patient was recommended to receive post-operative external beam radiation treatment to the chest wall. The patient gave informed consent to receive definitive radiation treatment.

In the past1 at our institution, we had encountered adverse affects in such patients having a temporary tissue expander in place and receiving radiation treatment. Three out of 10 patients, had to have their prosthesis removed due to complications. This had lead to unacceptable cosmetic results. One patient developed a leak in the prosthesis. In two other patients, undiagnosed damage to the prosthesis resulted in poor wound healing and seroma formation leading to tissue necrosis. Taking our previous experience into consideration, we obtained a series of radiologic images (CT scans) prior to, during and at completion of radiation treatment (fig 7 & 8). This enabled us to detect changes early and prevent any untoward changes. The CT images were used to monitor and record any possible changes in the temporary tissue expander itself and the surrounding structures adjoining the prosthesis.
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Figure 5. Mechanical stress and strain

Figure 5. Mechanical stress and strain of the prosthesis during radiation can cause the prosthesis to expand superiorly abnormally and extend beyond the planned radiation treatment field.

The patient, plastic surgeon and other members of the medical team were kept informed of our plan. The normal expansion of the prosthesis was achieved by injection of saline through a valve connected to the prosthesis. The expander was initially filled with 50 to 100 ml of normal saline through the connecting tube. Subsequent normal saline injections of approximately 50 ml were undertaken in 3 to 5-day intervals until the size and appearance of the breast mound was acceptable to the patient and the surgeon. Usually the expanded breast is about 150 to 200 ml larger than the projected size of the permanent prosthesis. To make sure that there were no volume changes in the prosthesis during radiation treatment, the amount of fluid in the prosthesis was kept constant (750 ml) following patient’s satisfaction with the size and appearance of the breast mound. This was done prior to initiation of radiation therapy and acquisition of the pre-treatment radiologic images. Moreover, the relative position of the prosthesis with respect to the surrounding structures was recorded. Comparisons were also made among the CT scans obtained during the course of radiation therapy to judge the geographical changes.

The external beam radiation treatment to the whole breast mound (fig 6) consisted of a standard protocol of 5040 cGy in 180 cGy fractions, via 6 MV photon tangents, given over a period of 6 weeks124.

Figure 6. The external beam radiation treatment

Figure 6. The external beam radiation treatment to the whole breast mound consists of a standard protocol of 5040 cGy in 180 cGy fractions, via 6 MV photon tangents, given over a period of 6 weeks

We also undertook additional studies on the effects of improper expansion of a breast prosthesis using the “Alderson-Rando” body-shaped phantom, made of tissue equivalent material. We simulated various hypothetical geometries of prosthetic deformations. Radiologic simulations were obtained of these hypothetical conditions of improper expansions of the prosthesis. Dosimetry calculations were performed for each hypothetical simulation. Computerized calculations of the dosimetric variations were obtained. The photon dose distributions of these hypothetical conditions were compared to the dose distribution obtained on an unde-formed prosthesis.
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