5 fr Ultrahypofractionated WBI and SIB for Breast Cancer With Unfavorable Characteristics

Five Fractions Ultrahypofractionated Whole Breast Radiotherapy and Simultaneous Integrated Boost to the Tumor Bed, for Breast Cancer Patients With Unfavorable Characteristics

This is a prospective, randomized, single-center, non-inferiority interventional clinical trial comparing whole breast irradiation (WBI) to a total dose of 26 Gy in 5 fractions with simultaneous integrated boost (SIB) to the tumor bed to a total dose of 30 Gy, and WBI to a total dose of 40.05 Gy in 15 fractions with SIB to the tumor bed to a total dose of 48 Gy (standard treatment), for young or unfavorable breast cancer patients.

The project refers to a study on patients with T1-T3 Nx-N3 breast cancer, aged under 40 years or with unfavorable histology (lobular carcinoma, multifocal tumor, or histological subtypes Luminal B Her2 positive, Hormonal Receptors negative Her 2 positive, Triple Negative Breast Cancer-TNBC-) treated with breast-conserving surgery (BCS) and radiotherapy to the whole breast (+/- lymph node areas) to a total dose of 26 Gy in 5 fractions, with simultaneous boost (SIB) to the tumor bed to the total dose of 30 Gy, that will be compared with the current departmental standard of moderately hypofractionated radiotherapy to the whole breast, to 40.05 Gy in 15 fractions, with SIB to the tumor bed to a total dose of 48 Gy.

Inclusion Criteria:

1. Histological diagnosis of breast cancer
2. Patients younger than 40 years regardless of histological subtype, or patients between 40 and 70 years with lobular carcinoma, histological subtypes Luminal B Her2 positive, or with hormone receptors negative and Her2 positive (ErbB2), or triple negative (TNBC)
3. Signed informed consent
4. Clinical stage T1-T3, Nx-N3
5. Negative surgical margins (≥ 0.2 cm)
6. Clinical M0 in the previous 3 months
7. PS (ECOG) ≤2
8. No previous thoracic radiotherapy
9. Fertile women using contraceptive methods started during oncological treatment

Exclusion Criteria:

1. Patients with favorable characteristics (Luminal A, Luminal B Her2 negative, ≥ 40 years) undergoing partial irradiation
2. Patients who have undergone mastectomy
3. Multicentric tumors
4. Positive or close surgical margins (<0.2 cm)
5. BRCA1/2 positive (only if known)
6. Serious systemic diseases
7. Mental or other disorders that may prevent the patient from signing the informed consent
8. Previous invasive tumor, except skin cancer (excluding melanoma) unless the patient has been disease-free for at least 3 years (for example carcinoma in situ of the oral cavity or bladder)
9. Collagen or autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, scleroderma, Sjogren's syndrome)
10. Evidence of distant metastases (M1)
11. Contraindication to treatment systemic
12. Pregnant women
13. Non-compliance with the dose limits established in the treatment plan