ESTRO 2020 Abstract Book

S78 ESTRO 2020

PH-0164 A randomised clinical feasibility trial of a breast immobilisation device:The SuPPORT 4 All Project. H. Probst 1 , H. Reed 2 , A. Stanton 2 , C. Robertson 3 , R. Simpson 4 , S. Walters 4 , H. Simpson 5 , G. Brown 5 , K. Bryan- Jones 6 , S. Hielscher 5 , O. Din 7 1 Sheffield Hallam University, Faculty of Health and Wellbeing, Sheffield, United Kingdom ; 2 Sheffield Hallam University, Faculty of Science- Technology and Art, Sheffield, United Kingdom ; 3 Panache Lingerie, Design and Innovation, Sheffield, United Kingdom ; 4 Sheffield University, School of Health and Related Research, Sheffield, United Kingdom ; 5 Sheffield Teaching Hospitals NHS Trust, Radiotherapy Department Weston Park Hospital, Sheffield, United Kingdom ; 6 Sheffield Teaching Hospitals NHS Trust, Radiotherapy Physics, Sheffield, United Kingdom ; 7 Sheffield Teaching Hospitals NHS Trust, Clinical Oncology- Weston Park Hospital, Sheffield, United Kingdom Purpose or Objective Improvements in cancer specific and overall survival for women with early breast cancer have led to more focus on long-term toxicities of treatment. Whole breast radiotherapy has been shown to increase the risk of ischaemic heart disease (1) , symptomatic pulmonary fibrosis or a second primary cancer of the lung (2, 3) . Hence it is important to investigate methods to reduce radiation doses to these critical OAR. We have developed a novel support bra (S4A bra) to lift the breast away from the chest wall, particularly suited for women with larger breast size. The primary purpose was to test the feasibility of using the S4A bra for women undergoing whole breast irradiation and to determine acceptability of the pathway to patients and clinicians. Feasibility and efficacy endpoints were measured to inform the design of a future larger RCT and to confirm product safety. Material and Methods This was a single centre randomised feasibility trial. Eligible patients were assigned to either the S4A bra (group A) or standard positioning without immobilisation (group B) via computer-generated randomisation remote to the clinical and S4A project team; randomisation was stratified by breast size. All patients received 40Gy in 15 fractions over 3 weeks without a boost or regional nodal irradiation; no bolus was applied to any patients. Group A received two planning CT scans (using a repeated measure design); one wearing the S4A bra and one without the bra, to enable a direct comparison of OAR doses. Data on set up reproducibility were measured using 2D on

clinical practice (Table 1). A questionnaire was also distributed, in which for each case, an inventory was requested of which structures and dosimetry metrics were used during planning and evaluation. Additional information was requested on the possible compromise that could be made to PTV dose coverage. The benchmark results, in combination with a literature review, was then used to formulate a consensus proposal.

Table 1: Benchmark Cases

Results 19 out of 20 departments participated in this project. 1 institute did not participate due to time limitations. There was a wide variation in dose evaluation parameters used clinically. For example, PTVs were evaluated using 10 different combinations of dose/volume criteria. Although target coverage did not differ much between institutions, substantial OAR dose differences were observed (Figure 1). These differences were more pronounced for the cases including the lymph nodes. Only 6% of the radiation oncologists said to always take into account clinical factors, social factors and gene mutation when delineating the CTV-breast and CTV-lymph nodes. 44% said to take this sometimes into account and 39% never. In order to spare OARs, 61% of the radiation oncologists said that they sometimes make a compromise to PTV dose coverage without there being an established protocol, 28% would make a concession to the PTV dose coverage with an established protocol for this, and 11% said to adjust the delineation of the PTV when they want to do a conscious concession. The project group formulated a proposal with regard to both dosimetric and clinical parameters to be evaluated. The parameters are planned to be an extension to the Dutch Nabon Breast Cancer Audit-Radiotherapy indicators. The harmonization proposal was discussed at an inventational conference on October 11 th 2019. Figure 1: DVH parameter values relative to the average DVH parameter value over all institutions for case 1.

treatment images (5 images per patient). The following measures were included: • Skin reactions-RTOG (4) . •

Moist desquamation in the inframammary fold.

• •

Dose to OAR.

Patient comfort, modesty

and

(5)

empowerment (6)

•

Acceptance using an adapted technology acceptance tool (7) .

Conclusion There is large variation in both volume and dosimetric parameters used for calculation and evaluation of a radiotherapy treatment plan for breast cancer. Radiation oncologists take into account clinical factors when performing the target volume delineations and assessing the treatment plans. Mostly this consideration is based on own experience, without established protocols. Approval of the consensus guidelines for plan evaluation by the Dutch Platform for Breast Radiotherapy is expected in November 2019.

•

Body Image (8)

Results Population systematic errors for central lung depth was 0.9mm for the S4A arm and -1.5mm for the control (difference 2.4mm CI 0.9-3.9). There was a difference in systematic error in the cranial-caudal distance (CCD) 2.7mm (S4A bra) vs 1.5mm. Differences in random errors between the groups were all below 1mm except for CCD where there was a small difference in favour of the control arm (2.4mm difference). RTOG scores were comparable between the groups. No difference in mean heart dose was identified (mean heart doses all <1.5Gy) all left sided cases had DIBH. Table 1 shows mean ipsilateral lung dose when