In patients undergoing adjuvant radiotherapy for breast cancer, radiation-induced skin toxicities are a common occurrence and adversely impact patients' quality of life (QOL). In the last decade, there have been no significant advances in preventing or treating radiation-induced skin toxicities. Recently, a phase III randomized trial by Herst et al. (n=78) in New Zealand showed that the prophylactic use of Mepitel Film reduced skin reaction severity by 92% compared to skin treated only with aqueous cream. Mepitel film has not been widely adopted in North America. To validate the efficacy of the film and guide the development of a larger multi-centre phase II study, a pilot study testing the efficacy of the film is proposed. In the study, 30 patients will have the film applied on their breast for the duration of radiation treatment and their skin reactions will be assessed throughout the treatment and after the treatment. The investigators hypothesize that the severity and incidence rates of skin reactions for patients using Mepitel film will be lower when compared to real world data from our centre, and that cosmetic outcomes will be improved with the film.

In patients undergoing adjuvant radiotherapy for breast cancer, radiation-induced skin toxicities are a common occurrence and adversely impact patients' quality of life (QOL). Patients with large breasts or patients receiving chest wall radiation may be more likely to have worse skin reactions following radiation. In the last decade, there have been no significant advances in preventing or treating radiation-induced skin toxicities. Recently, a phase III randomized trial by Herst et al. (n=78) in New Zealand showed that the prophylactic use of Mepitel Film prevented moist desquamation (26% vs. 0%, p < 0.001) and reduced skin reaction severity by 92% (p < 0.001) compared to skin treated only with aqueous cream. Another study by Moller et al. (n=101) in Denmark reported a non-significant improvement in observer-rated radiation dermatitis with the film (p=0.1) compared to cream, and significant improvements in several patient-reported outcomes. Moreover, patients with breast cancer complain of hyperpigmentation in the radiated area during and after radiation.

Mepitel Film has not been widely adopted in North American clinical practice. To further study and validate the efficacy of Mepitel Film in preventing acute skin reactions caused by breast radiation and elucidate its efficacy in preventing poor cosmetic outcomes, a phase II efficacy study of three patient populations will be conducted:

1. Patients with large breasts
2. Patients with small or medium sized breasts
3. Patients with chest wall radiation

The results of the phase II efficacy study can guide the development of a subsequent multi-centre phase II and III trials to further validate the use of Mepitel film and increase its adoption rate.

The primary objective is to examine the efficacy of Mepitel film in the prophylaxis of radiation-induced skin reactions. Secondary objectives include an evaluation of patient-reported and healthcare professional (HCP)-reported skin toxicities including moist desquamation with the use of Mepitel film.

Radiation oncologists will first introduce the study to their patients in their breast clinic, showing a sample of the product and also pictures from the trial conducted in New Zealand. Patients if interested may be provided a patient information sheet to review at home. Then, patients will be approached by a CRA at their radiation planning appointment to review all information and obtain informed consent.

All patients will receive Mepitel film for the duration of treatment. Radiation treatment will be delivered as prescribed by the treating radiation oncologist and may include a variety of techniques and beam modifiers.

Trained clinical research assistants (CRA) or the radiation review nurse will apply the Mepitel film for patients prior to their first radiation treatment at a designated clinic room and will check daily prior to radiation that the breast/chest wall has not been distorted by the film. If the film needs to be readjusted, the CRAs or nurses will remove peeling sections of film and reapply where needed. The film will be removed two weeks post radiation treatment.

Patients will complete evaluations once a week at their regular review clinic visit and will be assessed by an HCP or CRA. At the last treatment or last review appointment, a photo of the patient's breasts/chest wall will be taken, and they will be asked to complete an assessment. An HCP will also conduct an assessment.

After completion of radiation, patients will be called at week 1 and weeks 3-6 to assess endpoints. Patients will be asked to return for a 2-week, 3-month, and 6-month follow-up assessment where photos of their breasts/chest wall will be taken, and they will complete their personal assessments. The film will be removed at the 2-week follow-up appointment. The 3-month follow-up assessment will occur at the same time as their regular clinic follow-up with their radiation oncologist. At the 3-month and 6-month follow-up assessment, an HCP will also an assessment.

Inclusion Criteria:

• Informed consent
• Patient will receive adjuvant breast or chest wall radiation
• Post-lumpectomy patients with band size of at least 36 inches or cup size of D or larger will be part of the large breast cohort
• Post-lumpectomy patients that do not meet this size requirement will be part of the small or medium sized breast cohort
• Post-mastectomy patients are part of the chest wall radiation cohort
• Can communicate in English or be aided by a hospital translator

Exclusion Criteria:

• Patient had previous radiation therapy to the treatment area
• Patient had breast reconstruction
• Patient has a Karnofsky Performance Status score <70
• Patient will have radiation treatment in prone or reverse decubitus positions
• Patient will receive partial breast external beam radiation or brachytherapy
• Patient will receive radiation to the supraclavicular region