Aeroform carbon dioxide tissue expander device is a novel alternative system to the traditional saline tissue expanders for patients who have had mastectomy for breast cancer and require adjuvant radiation therapy (RT). However, the metallic reservoir within the device poses a significant impact on RT dosimetry while treating the chest wall area. The aim of this study is to compare RT dosimetry outcomes using volumetric modulated arc therapy (VMAT) versus tangential intensity-modulated radiation therapy (t-IMRT) techniques when planning post-mastectomy RT, using the recent ESTRO-ACROP target...

Five patients with left sided breast cancer who underwent mastectomy, axillary dissection, carbon dioxide tissue expander insertion were identified. Retrospectively, their CT simulation planning scans were utilised to delineate the ipsilateral chest wall (CW) and nodal target volumes as per ESTRO consensus guidelines. A dose of 50.4Gy in 28 fractions was prescribed and four plans generated to consider VMAT and t-IMRT to the left CW, supraclavicular fossa (SCF), with and without internal mammary nodes (IMN). Dosimetry for all target volumes and organs at risk were...

When comparing VMAT with t-IMRT techniques, there was no statistically significant difference in the planning target volume receiving 50.40Gy (PTV5040) D95 or D2 coverage (p=0.122, p=0.816, respectively). Within t-IMRT plans, excluding IMN leads to higher D95 coverage (p=0.002). The heart mean dose and V25 were significantly lower with VMAT than t-IMRT (p<0.001). There was no significant difference to the heart dose whether IMN was included or not. The ipsilateral lung V20 was significantly lower with VMAT than t-IMRT (p<0.001), but not the V5 (p=0.246). Within...

VMAT technique was able to achieve a lower mean heart dose, ipsilateral lung V20, ipsilateral ribs and intercostal muscle minimum dose, than t-IMRT technique. However, it is also associated with higher absolute dose values to contralateral lung and right breast, whilst maintaining similar target volume coverage. Each patient should be considered individually by their risk factors when deciding which planning technique to use.

[1] Kaidar-Person, O., et al., ESTRO ACROP consensus guideline for target volume delineation in the setting of postmastectomy radiation therapy after implant-based immediate reconstruction for early stage breast cancer. Radiother Oncol, 2019. 137: p. 159-166.