Elsevier

Brachytherapy

Volume 4, Issue 3, 2005, Pages 224-229
Brachytherapy

CT computer-optimized high-dose-rate brachytherapy with surface applicator technique for scar boost radiation after breast reconstruction surgery

https://doi.org/10.1016/j.brachy.2005.03.003Get rights and content

Abstract

Purpose

Immediate breast reconstruction has become increasingly prevalent after mastectomy for breast cancer. Postoperative scar boost radiation for the reconstructed breast presents many planning challenges due to the shape, size, and curvature of the scar. High-dose-rate (HDR) surface applicator brachytherapy is a novel and effective method of delivering scar boost radiation. Two cases, one with a saline implant and one with a transverse rectus abdominis musculocutaneous flap reconstruction, illustrate the method and advantages of HDR optimization of surface applicators.

Methods and materials

For 2 patients a mold of the breast was made with Aquaplast sheets. A reproducible system was used for arm positioning. Skin fiducials, including tattoos from external beam planning, were matched to fiducials on the mold. HDR catheters were sited on the mold at 1 cm intervals, with the central catheter situated along the scar. Topographically, both scars demonstrated extreme curvature in both craniocaudal and mediolateral directions. A CT computer-optimized HDR plan was developed, with the reference dose prescribed at the skin surface. The dosimetry was compared to single-field and matched-field electron plans.

Results

This surface applicator technique provided a uniform skin dose of 100% to the entire clinical target volume (CTV) without hot spots in both patients. The patient position and surface applicator setup were consistently reproducible. The patients tolerated the treatment well with minimal skin erythema. In the single-field electron plan, skin dose was decreased to 50% at the periphery of the scar. Matching fields addressed this depth dose decrement, but resulted in large localized hot spots of more than 200% centrally in each field.

Conclusion

CT computer-optimized HDR surface applicator brachytherapy provided a reproducible homogeneous method of treating highly curved scars on the reconstructed breast. Electron beam treatment would result in longer and more complex treatments yet still provide a less homogeneous dose than this surface applicator technique.

Introduction

Immediate breast reconstruction after mastectomy for breast cancer has become increasingly prevalent (1). Because mastectomy is frequently chosen for the treatment of locally advanced breast cancer, postoperative radiotherapy is often indicated. Therefore, the number of reconstructed breasts requiring adjuvant postoperative irradiation is also likely to increase. Postmastectomy radiotherapy has been shown to decrease locoregional recurrence and increase disease-free and overall survival when added to systemic therapy for postmastectomy patients [2], [3], [4]. The rationale for scar boost irradiation is based not on prospective clinical trials but rather on clinical observations of patterns of recurrence. Boost irradiation of the reconstructed breast can present many planning challenges due to the size, shape, and curvature of the resulting scar.

Surface applicator irradiation is one of the oldest forms of radiotherapy. The construction of wax and paraffin skin molds using radium needles and radon seeds was described at the turn of the 20th century (5). The use of these decreased due to radiation protection issues and the emergence of teletherapy. However, with the introduction of high-dose-rate (HDR) brachytherapy afterloader technology, the use of surface applicators is increasing again. Surface applicators of various designs have been described in the treatment of basal cell and squamous cell carcinoma of the face (5), Kaposi's sarcoma (6), and recurrent chest wall disease even after previous irradiation for breast cancer (7). A novel and effective use of surface applicator technology to deliver adjuvant scar boost irradiation to 2 patients with highly curved scars resulting from breast reconstruction surgery with both saline implant and transverse rectus abdominis musculocutaneous (TRAM) flap reconstruction is presented.

Section snippets

Methods and materials

Two patients underwent mastectomy with immediate reconstruction for breast cancer. Patient 1 received a saline implant and patient 2 had a TRAM flap reconstruction. Both surgical procedures resulted in scars that demonstrated extreme curvature in both craniocaudal and mediolateral directions. The patients were given external beam radiotherapy of 50.4 Gy in 28 fractions to the entire chest wall, including the reconstruction, and presented for additional radiation to the chest wall surgical

Results

Individualized dose optimization allowed the HDR surface applicator to provide a uniform skin dose of 100% to the whole target in both patients. The 80% isodose line lay at a distance beneath the skin surface of 8.4 mm in patient 1 and 6.5 mm in patient 2. This slight variation between patients was due to a difference in the thickness of Protoplast sheet (WFR/Aquaplast Corp.) after it had been stretched slightly during the molding process. Figures 3a and 4a are axial images showing the

Discussion

In patients undergoing mastectomy, the most common area of local recurrence is within the area of the surgical scar [8], [9]. Therefore, administration of additional radiation to the area of the chest wall incision after radiation to the entire chest wall is often a method of choice in patients who have undergone mastectomy for locally advanced breast cancer.

A tumor bed boost has been shown to significantly decrease local recurrence, even after wide local excision with negative margins, after

Conclusion

The use of HDR surface applicator technology in administering a radiation boost to the scar resulted in a homogeneous and easily reproducible treatment that was acceptable to the patients. The brachytherapy dosimetry was superior to single-field and matched-field electron treatment at the skin surface. This radiotherapy technique may also be useful in cases of disease relapse within the reconstructed breast. With increased patient numbers, this method of radiation delivery should be subjected

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