The purpose of this study is to characterize the skin microbiome profile of breast cancer patients before and after receiving Radio Therapy treatments, and evaluate the relationship between the microbiome profile and radiation dermatitis severity (grade) that the patient will develop. Such characterizations can lead to potential biomarkers and/or therapeutic targets that can be used for the prognosis, prevention and treatment of this condition.

Inclusion Criteria:

1. Age ≥ 18 years
2. Histological confirmation of breast malignancy
3. Primary or recurrent disease eligible
4. Patients after breast lumpectomy and that scheduled to receive radiotherapy
5. Patients that receive minimum of 45 Gy
6. Ability to complete questionnaire(s) by themselves or with assistance
7. Provide informed written consent

Exclusion Criteria:

1. Patients with prior radiotherapy to any portion of the planned treatment site
2. Tumour involvement of the skin
3. Patients with active rash, pre-existing dermatitis, lupus, or scleroderma
4. Patient with other skin diseases/ skin disorders
5. Recent use of systemic or topical antibiotics or antifungal medications within 21 days of first swab collection.
6. Recent use of any of the following within 21 days of first swab collection: o Systemic or topical steroids o Use of systemic immunosuppressant drugs o Use of ultraviolet light therapy
7. Prior usage of other topical and systemic medications within 21 days of first swab collection
8. Prior usage of topical cosmetic products, creams, lotions, or gels within 14 days of first swab collection in areas where samples are taken.
9. Clinical evidence of infection that in the judgement of the principle investigator would interfere with proper assessment of the skin microbiome
10. Prior organ or bone marrow transplant
11. Any other reason that, in the opinion of the investigator, prevents the subject from participating in the study or compromise the patient safety

Patients with breast cancer undergoing radiation therapy.