Feasibility evaluation of prone breast irradiation with the Sagittilt^© system including residual-intrafractional error assessment

Feasibility evaluation of the Sagittilt^© prone breast board system (Orfit Industries, Wijnegem, Belgium) for radiotherapy focusing on patient and staff satisfaction, treatment time, treatment reproducibility with the assessment of residual-intrafractional errors.

Thirty-six patients underwent whole-breast irradiation in prone position. Seventeen received a sequential boost (breast: 42.56Gy in 16 fractions, boost: 10Gy in five fractions), while 19 patients received a concomitant boost protocol (breast/boost: 45.57/55.86Gy in 21 fractions). Treatment verification included a daily online cone-beam CT (CBCT). In order to assess the residual and residual-intrafractional errors post-treatment CBCTs were performed systematically at the first five treatment sessions. Treatment time, patient comfort, staff satisfaction were also evaluated.

The pretreatment CBCT resulted in a population systematic error of 4.5/3.9/3.3mm in lateral/longitudinal/vertical directions, while the random error was 5.4/3.8/2.8mm. Without correction these would correspond to a clinical to planning target volume margin of 15.0/12.3/10.3mm. The population systematic and random residual-intrafractional errors were 1.5/0.9/1.7mm and 1.7/1.9/1.6mm. Patient and staffs' satisfaction were considered good and average. The mean treatment session time was 21minutes (range: 13-40min).

The Sagittilt^© system seems to be feasible for breast irradiation and well-tolerated by patients, acceptable to radiographers and reasonable in terms of treatment times. Set-up accuracy was comparable with other prone systems; residual errors need further investigations.