Efficacy Study With StrataXRT for the Prophylaxis of Radiation Dermatitis in Adjuvant Breast Radiation Treatment in Large Breasted Women Using a Prone Technique

For breast cancer patients undergoing adjuvant radiotherapy, radiation dermatitis (RD) is a common occurrence that can negatively impact patients' quality of life (QOL). RD often presents as erythema, pruritus, and/or edema and in more severe cases, skin breakage can occur, resulting in moist desquamation. In a study published, it was found that for women with large breasts (n=357), being positioned in the supine position during radiation could lower the rates of moist desquamation from 36.9% in the supine position down to 26.9% when treated in the prone position. Even though the prone position for patients with large breasts did reduce rates of moist desquamation, these results demonstrate that one in five patients still go on to develop severe reactions, even in the prone position. Building on these results, a phase II feasibility study conducted at Sunnybrook, found that the use of a silicone-based film forming topical gel known as StrataXRT could lower the incidence of moist desquamation for patients treated in the prone position even further. This currently unpublished study identified that only 10% of patients treated in the prone position using the prophylactic StrataXRT gel experienced grade 2 RD with moist desquamation, and no patients experienced grade 3 RD compared to 26.9% % of patients treated in prone that use the current standard of care moisturizer. Due to StrataXRT being a silicone-based film forming topical gel, it is very flexible and can be applied easily to the prone position and to the contours of the large breast unlike some other barrier film skin interventions.

StrataXRT has previously also been shown to be non-inferior to another silicone-based barrier film known as Mepitel film in the prevention of RD. A study by Chao et al compared the rates of moist desquamation and RD CTCAE scoring in 44 breast cancer patients. Medial and lateral halves of the breast were covered with Mepitel Film and StrataXRT. The results showed no significant differences in the rate of moist desquamation or severity of RD assessed on the CTCAE between groups. This study also noted that nurses had to be responsible for the application of the Mepitel Film, with the average time of application reported to be 15 minutes. In comparison, the StrataXRT was applied and maintained by the patients, and did not require dependency on nursing resources.

Other studies have shown benefits of StrataXRT . A recent randomized control trial published in 2022 by Omidvari et al found that in breast cancer patients (n=100), the use of StrataXRT significantly reduced the mean size of the radiation-induced dermatitis area (p=0.002) when compared to the control group. Additionally, RD as scored by the CTCAE was found to

be significantly more severe in the control group in weeks 1-5, except for week 4 where no significance was indicated. Another randomized control trial (n=49) demonstrated significant differences in the Erythema Index (EI) (p=0.001) and Melanin Index (MI) (p=0.005) between StrataXRT compared to the use of Xderm, a moisturizer. The EI and MI are alternative methods of measuring RD, using electrochemical reflectance most often with a handheld spectrophotometer. However, this tool is not the standard measurement for assessing RD and therefore these results are difficult to compare to other studies. There was no significant difference found between groups using physician assessed outcomes. However, this was likely due to the patient population being at low risk of severe skin reactions, and subsequently no patient in either cohort developed moist desquamation over the course of the study. No added risks or adverse events, other than mild irritation, have been reported following the use of StrataXRT in the aforementioned trials.

In the phase II feasibility study completed at Sunnybrook Odette Cancer Centre, the patient reported outcomes were also favorable and showed promising results for StrataXRT. When analyzing a patient satisfaction questionnaire completed with the prone patients of the study, seven out of eight (88%) patients reported that they felt moderate to high levels of skin protection from StrataXRT. Additionally, all but one patient felt that StrataXRT was easy to apply, and that they had a positive experience with the gel. Patient QOL was evaluated using the Skindex-16 questionnaire, a tool scored out of 96, with a higher score indicating worse QOL overall. In the prone population, the mean total Skindex-16 score was 16.90 out of 96, highlighting that the use StrataXRT was beneficial for patient QoL. In the study conducted by Vesprini et al, secondary outcomes such as clinician-reported grade 2 pain, grade 2 erythema, and grade 1 edema were collected using the CTCAE scale. The incidence of these symptoms was 5.1%, 77.1%, and 48.0% respectively. In the feasibility study on StrataXRT, similar results were extracted using a skin symptom assessment (SSA) and it was found that 10% of patients experienced grade 2 pain, 10% experienced grade 2 erythema, and 10% experienced grade 1 edema. Based on these preliminary results, it is hypothesized that StrataXRT may also lower both erythema and edema substantially.

Due to the limited number of patients in the previous prone cohort (n=10), the investigators would like to consolidate these results by repeating the prone cohort with a larger patient population. The investigators propose to repeat this feasibility study by enrolling 20 additional patients treated in the prone position to confirm these promising results before moving to a phase 3 RCT. Based on the results of our phase II feasibility study, StrataXRT has been well tolerated by patients, is feasible to integrate into daily clinic flow and appears to reduce rates of moist desquamation in patients treated in prone and the incidence of grade 3 radiation dermatitis in this cohort. StrataXRT, though Health Canada approved (License No.: 95612) already, is not commonly used in clinical practice in Canada. There is a need to further study and validate the efficacy of StrataXRT in the prevention of RD for patients with large breasts (minimum of band size of 40 inches or cup size D) treated in the prone position-breast radiation only (boost allowed).