Background and importance Stomatitis is a class effect associated with inhibition of mTOR and is associated with everolimus therapy for breast cancer. Topical steroids might reduce the incidence and severity of stomatitis.

Aim and objectives To describe the population treated with everolimus and evaluate the effectiveness of dexamethasone mouthwash 0.1 mg/mL for prevention of stomatitis in patients with metastatic breast cancer treated with everolimus–exemestane.

Material and methods A retrospective observational study was carried out from January 2012 to 2019 in a tertiary hospital. We included patients with breast cancer who were treated with everolimus–exemestane and collected it at the outpatient pharmaceutical care unit of the hospital pharmacy. Demographics and clinical parameters were collected from the medical history: age at the beginning of the treatment, dose, duration of treatment, adverse reactions and reason for suspension of therapy. The incidence of mucositis was recorded and a comparison was made between patients who initiated prophylaxis with dexamethasone mouthwash 0.1 mg/mL versus those who did not.

Results A total of 24 patients were evaluated. Mean age was 61 (39–82) years. Treatment with everolimus–exemestane was a secondline antineoplastic treatment in 54% (n=13) of patients. For the remaining 46% it was a thirdline treatment or later. Prophylactic treatment with dexamethasone mouthwash was initiated in 50% of patients (from January 2017).

All patients began treatment with everolimus at a dose of 10 mg daily. Of these, 38% (n=9) required a reduction to 5 mg daily due to toxicity: intense asthenia (n=3), pneumonitis (n=1), skin rash (n=1), oedema in the lower limbs (n=1), thrombopenia (n=1), neutropenia (n=1) and persistent nausea and vomiting (n=1).

A total of 88% of patients discontinued treatment due to radiological progression of the disease. The average treatment duration was 5.9 months. In no case was the treatment terminated due to adverse effects.

Regarding the efficacy of dexamethasone mouthwash, in patients who did not use the oral solution (n=12), the incidence of stomatitis was 67% (grade 1, n=5; grade 2, n=3). This delayed the antineoplastic treatment in 2 patients (25%; n=2). In patients who used dexamethasone mouthwash (n=12), one patient presented with stomatitis (grade 1).

The use of dexamethasone mouthwash 0.1 mg/mL was associated with a statistically significant decrease in the incidence of stomatitis (χ² <0.05). No adverse effects associated with the oral solution were detected.

Conclusion and relevance Prophylactic use of dexamethasone mouthwash reduced the incidence and severity of stomatitis in patients receiving everolimus–exemestane.

References and/or acknowledgements No conflict of interest.