Breast Treatment Planning

Motion Management for Breast Radiotherapy

In breast radiotherapy, breathing motion presents a unique challenge, especially for the left breast. As close as it is to the anterior chest wall, the heart can receive significant dose if no mitigation techniques are implemented. Patients selected for motion management for breast radiotherapy were predominantly left breast according to survey data, with 87.5% of clinicians stating they only gate left breast.

According to the 2017 survey, 76.7% of clinicians used some form of motion management for breast treatment. The majority (71.4%) used either Varian RPM/RMM or Vision RT as their equipment of choice, though other options exist. Of those that chose to gate, 73.3% of those do so by directly interfacing with the linac for automatic gating and 26.7% employ some sort of manual gating.

Among clinicians that use motion management techniques for breast, 89.1% used verbal or visual feedback to coach the patient through gating cycles. Visual gating was achieved using goggles in 58.3% of clinics and an in-room display in 41.7%.

Types of Feedback Used in Breast Gating

Imaging for DIBH

Breath-hold gating is a common motion management solution that creates space between the field borders and the heart, greatly limiting heart dose in a majority of patients. Deep-inspiration breath-hold (DIBH) is a popular gating method in which the patient inhales deeply and holds their breath during imaging and treatment. To ensure the accuracy of the inhale positioning, the patient is imaged prior to treatment. In a recent 2020 survey, 62.7% preferred imaging with weekly MV ports. Of those that imaged MV ports once per week, 34.4% were satisfied with weekly ports alone while 37.5% supplemented with daily SGRT.

Filming MV ports at the beginning of the treament course was the option of choice for 17.6% of respondents, coupled with either daily kVs or daily SGRT. The least common options for DIBH imaging were daily MV at 11.8% and daily kV at 7.8%. It was almost unanimous that clinicians do not use MV CINE imaging to verify DIBH, with 94.0% indicating they never use it for DIBH.

Imaging Protocol for Breast Tangents

Combined serial data from 2014 and 2019 showed that for the treatment of simple breast tangents, a large majority of respondents (91.3%) image using weekly MV ports in some form or fashion. The remaining clinicians used a combination of daily setup pairs (MV and/or kV) and daily CBCT.

Eclipse Breast Planning Methods

When it comes to breast treatment planning, tangents are the modus operandi for standard cases. A whopping 73.9% of 2016 survey takers said they generate tangent plans using the Field-in-Field (FIF) technique. Others admitted to using irregular surface compensator (9.9%), 6.8% used electronic dynamic wedges (EDWs), 5.6% used an electronic compensator, 3.1% used full or hybrid IMRT, and 0.6% used a physical wedge. For those that claimed to use irregular surface and electronic compensators, the techniques were almost exclusively used for breast treatment, with 97.2% and 94.4% of respondents noting they don’t use those techniques for any other body sites.

Prone Breast Treatment Methods

Some clinicians prefer treating breast patients in a prone position. By lying prone, the breast is pulled away from the body, enabling improved PTV dose homogeneity and sparing dose in cardiac and lung tissue. Because prone planning poses a variety of challenges—like additional equipment and larger bore scanners—only 53.9% treat “some” patients with it. A survey from four years earlier (2015) showed similar prone treatment usage at 43.6%. For those that performed prone treatment, 71.4% had a large bore CT scanner, and 61.5% of clinicians noted using the technique in a majority of cases with patients with pendulous breasts.

Breast Setup and Immobilization

The reverse of the prone setup is employed more commonly. In the standard supine treatment, the patient’s arms are placed above their head in a stable position to move them from the direct beam and limit motion. The most common immobilization, according to a 2020 survey, was a breast board at 54.2%, followed by a wing board at 25.0%. Some 16.7% used both depending on the case, and 4.1% used an arm shuttle. Users commented that the breast board was the most common since it can be used on patients of all sizes, unlike wing boards, which suffer from stability issues with larger patients.

Breast Flash with VMAT

While VMAT usage is relatively rare compared to other breast tangent techniques like FIF, almost a third (32.1%) of 2016 survey takers used it to treat breast or chest wall cases. Of those that used VMAT, 66.0% generated flash around the external contour. The most common choice method was to optimize on fake bolus and perform a PTV expansion.