A Topical Betamethasone Versus Moisturizer in Preventing Radiation Dermatitis in Large-Breasted Patients Treated in the Prone Position: A Randomized Phase III Trial

Radiotherapy (RT) is common in the treatment of breast cancer, however, 95% of breast cancer patients are at risk of developing acute and chronic skin toxicities known as radiation dermatitis (RD) which includes symptoms such as pruritus, edema, erythema, and moist desquamation (MD). Patients with a larger breast size are especially at risk of developing RD. The severity of RD can impact patient's quality of life (QOL) and their ability to complete treatment. Skin care guidelines for patients receiving RT vary and include barrier films and dressings, antibiotics, topical corticosteroids, and moisturizers. A study conducted at the Sunnybrook Odette Cancer Centre investigated the effectiveness of the prone treatment position during RT compared to the supine position. The results indicated that the prone position reduced the incidence of MD from 39.6% in supine to 26.9% in prone. However, 1 in 4 patients in the prone position still develop MD. Another study conducted at Sunnybrook Odette Cancer Centre found that Mepitel Film (MF), a barrier film, is more effective than the standard of care in preventing grade 2 or 3 RD, reducing the incidence of grade 2 or 3 RD from 45% to 15%. Despite its effectiveness, MF cannot be used for patients in the prone position and is costly. The topical corticosteroid betamethasone can prevent skin toxicity through its anti-inflammatory properties and is absorbed by the skin with minimal side effects. Betamethasone is cost-efficient and studies have found that it is effective in reducing the severity of RD in the supine position by half. Moreover, betamethasone can be applied in patients positioned in both prone and supine. The investigators hypothesize that adding betamethasone in large-breasted patients treated in prone during RT will further reduce RD. This randomized control trial is the first of its kind to aim at investigating the effectiveness of betamethasone when compared with the standard of care in reducing the severity of RD in large-breasted patients being treated in the prone position during RT. The investigators will enroll 276 breast cancer patients with band size ≥ 40 or ≥ D cup to be randomized to receive 0.1% betamethasone cream or the standard of care in a 2:1 ratio (alpha = 5% and power = 80% with the hypothesis that the addition of betamethasone to prone reduces the severity of RD from 30% to 15%). Upon enrolment, stratification factors will be recorded, and patients will be randomized into trial arms using procedures that balance stratification factors. All eligible patients will be stratified according to the following factors: patients receiving conventional RT (50Gy/25#) versus hypofractionated RT (40Gy/15#) versus extreme-hypofractionated RT (26Gy/5#), whole or partial breast radiation, patients with Fitzpatrick skin type VI versus patients with Fitzpatrick skin type I-V, patients receiving a planned boost versus patients without planned boost. The CRA will be responsible for collection of assessments and photos from patients. Patients will use the assigned cream daily during RT treatment and up until 2 weeks after RT. The primary endpoint of this study is acute grade 2 or 3 toxicities as defined by the Common Terminology Criteria for Adverse Events v5.0. Secondary endpoints will include patient- and clinician-reported outcomes as assessed by the Skin Symptom Assessment and the Radiation-Induced Skin Reaction Assessment Scale. Moreover, the investigators will also employ a QOL tool, the Skindex-16, and a Patient Satisfaction Questionnaire. Patients will complete assessments weekly during RT and 2 weeks post-RT in person, followed by 6 weekly assessments and a 3-month telephone follow-up post-RT. Clinicians will assess patients weekly during RT and at the 2-week follow-up appointment.