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Prone breast radiation therapy (RT) can improve the RT toxicity profile, but discomfort and imprecise breast positioning limit its use. Adopting a positioning aid could solve these problems.

We report on the results of the VENUS SHELL study, a proof-of-concept study simulating and evaluating time required for patient (pts) positioning, comfort, positioning accuracy and ability to self-position when using personalized, MRI compatible, shells for breast RT in prone position.

We enrolled 20 pts, age ≥ 18 years, WHO performance status ≤ 2 undergoing adjuvant RT after surgery. Exclusion criteria included allergies to plastic substances or medical dressings, body weight >90 kg, current pregnancy, and mastectomy without breast reconstruction.

A shell was made based on a surface scan of the body with the pts lying on a table having a transparent element to control, shape and image the region to be immobilized. Ultra-low dose CT scans of pts on the treatment board, 3 with and 3 without shell, simulated planning and repeated treatment. The time required to preposition the pts before each CT and their ability to self-align were measured. Automatic registration of images between the first (reference) CT and the verification (second and third) CTs was used to assess pre-positioning accuracy. The anterior breast to sternum distance was calculated from the CT as a breast pendularity parameter. Comfort was studied through pts surveys.

The median age (range) of the pts was 59 years (41-80), with cup ranging from A to G, 5/15 right/left-sided breast, and median body mass index of 24 (17-32) kg/m2. One pt was excluded from this analysis due to an incorrect procedure. Although there was no significant difference for pre-positioning time with shell versus without shell mean 2 min P = 0.24, when using the shell, the accuracy of pre-positioning increased significantly, see figure, with mean±std.dev translation distance of 1.3±0.8 mm with shell compared to 37±26 mm (P<<0.001) without, and maximum absolute yaw, roll, and pitch average angle of 0.03±0.06° versus 1.02±0.95° respectively (P<<0.001). Without a shell, pts were never able to self-position, whereas with the shell 14/19 pts self-positioned at least once and 7/19 at each CT session. Self-positioning did not require additional adjustments in 9/19 pts at the first repositioning assessment and in 12/19 pts at the second assessment. No significant differences were detected in time, pre-positioning accuracy, and self-positioning by age, BMI, or pts cup . Pendularity did not influence time to pre-position. The prone position was considered more comfortable when using the shell 17/19 pts than without 8/19 pts (P=0.005) with a reduction of the need to move passing from 6 to 1 pts out of 19 when using the shell (P=0.03).

Venus shell™ allows for easy, comfortable, fast and precise positioning of patients, making it a promising solution for breast SBRT treatments.