Adjuvant Partial-breast Irradiation Using Stereotactic Body Radiation Therapy

Early-stage breast cancer patients after partial mastectomy are screened for eligibility. The inclusion criteria are age ˃ 50 years, non-lobular carcinoma histology, size ≤ 2 cm, negative margins ≥ 2 mm, L0, ER-positive, HER-2 negative. Enrolled patients are equally randomized into two arms according to radiotherapeutic regiment - external beam APBI (5× 6 Gy) and accelerated whole breast irradiation with the boost (15× 2,67Gy + 5× 2Gy). The follow-up visits are planned at the end of RT and 1, 3, 6, 9, and 12 months after radiation, in the second year every 4 months and then every 6 months. Cosmetics results and toxicity are evaluated using questionnaires, CTCAE criteria, and photodocumentation of the irradiated chest. The main objective of presented study is to evaluate the feasibility, safety, tolerance, and cosmetic effects of SBRT irradiation to the surgery bed in five fractions. In addition to standard clinical examination and evaluation of acute and late side effects, patients together with clinicians and nurses will independently complete a questionnaire on the impact of irradiation on the cosmetic effect. The technique of targeted external beam APBI should demonstrate better feasibility and less toxicity than the standard regimen in the adjuvant setting in treating early-stage breast cancer patients. Consequently, the presented study should increase the level of evidence for RT-indicated patients to the establishment of external APBI into daily clinical practice.