This assessor-blinded randomized controlled trial aims to evaluate the efficacy of polarized polychromatic non-coherent light therapy as an adjunct to standard skin care in reducing acute radiation dermatitis in women with breast cancer undergoing hypofractionated whole-breast radiotherapy. Participants will be randomly allocated to receive either standard skin care alone or standard care combined with polarized light therapy initiated from the first radiotherapy session. Outcomes will include objective ultrasound-based dermal thickness measurements, clinical severity of radiation dermatitis using Radiation Therapy Oncology Group (RTOG) criteria.

Acute radiation dermatitis is one of the most frequent adverse effects associated with breast cancer radiotherapy and may negatively affect patient comfort, treatment adherence, and quality of life. Clinical manifestations range from mild erythema and dry desquamation to severe moist desquamation and ulceration. Although standard skin care measures are routinely implemented, effective preventive and therapeutic non-invasive interventions remain limited.

Polarized polychromatic non-coherent light therapy has demonstrated anti-inflammatory, microcirculatory, tissue regenerative, and wound-healing effects in several dermatologic and musculoskeletal conditions. However, evidence regarding its efficacy for radiation-induced skin toxicity remains insufficient.

This prospective randomized assessor-blinded controlled trial will investigate the effectiveness of polarized light therapy as an adjunctive supportive treatment for acute radiation dermatitis in women receiving hypo fractionated whole-breast irradiation (40-42.5 Gy in 15-16 fractions over approximately 3 weeks) following breast-lumpectomy for breast cancer.

Participants will be randomly assigned into two parallel groups:

1. Polarized light therapy plus Standard skin care.
2. Standard skin care alone. The polarized light intervention will be initiated on the first day of radiotherapy and administered three times weekly throughout the radiotherapy course using the Bioptron Light Therapy System.

The primary outcome will be ultrasound-based dermal thickness changes within the irradiated breast region. Secondary outcomes will include clinical severity of radiation dermatitis using Radiation Therapy Oncology Group (RTOG) criteria Assessments will be conducted at baseline, Week 2, Week 4, Week 6, Week 8, and at 2-month follow-up. The study aims to determine whether polarized light therapy can reduce radiation-induced skin inflammation, delay progression of dermatitis severity, improve symptom burden, and enhance skin recovery compared with standard care alone.

Inclusion Criteria:

1. Female patients aged 35-55 years.
2. Histologically confirmed primary unilateral breast cancer.
3. Status post breast-conserving surgery (lumpectomy).
4. Planned for hypo fractionated whole-breast irradiation (HFWBI).
5. Scheduled to receive a total radiation dose of 40-42.5 Gy delivered in 15-16 fractions over approximately 3 weeks.
6. Ability to understand study procedures and provide written informed consent.

Exclusion Criteria:

1. Previous radiotherapy to the same breast or thoracic region.
2. Bilateral breast cancer.
3. Metastatic or advanced systemic disease.
4. Prior mastectomy.
5. Active skin infection in the irradiated area.
6. Pre-existing dermatologic disorders affecting the breast skin (e.g., eczema, psoriasis, dermatitis).
7. Concurrent chemotherapy during radiotherapy.
8. Presence of cardiac pacemaker or implantable electronic device in the treatment field.
9. Open wounds or ulceration in the irradiated breast region.
10. Any medical condition judged by the investigator to interfere with study participation or outcome assessment.

Outcome assessors responsible for ultrasound imaging, clinical skin assessment, and data collection will remain blinded to group allocation throughout the study period.