Can fewer, stronger radiation doses match standard treatment after mastectomy?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Female * Age18-75 years * Pathologically confirmed invasive breast cancer * Treated with mastectomy and axillary lymph node dissection with more than 10 resected lymph nodes. Immediate or delayed ipsilateral breast cancer reconstruction is accepted * Negative surgical margins * Pathologic T1-2N1 with at least one of the following risk factors: \<40 years, Grade 3, lymphovascular invasion positive, ER/PR negative or HER2 overexpression, or pT3-4, or pN2-3 (four or more positive axillary lymph nodes) * No distant metastases * No supraclavicular or internal mammary nodes metastases * ECOG:0-1 * Adjuvant systemic therapy with chemotherapy, endocrine therapy and anti-HER2 treatment is accepted. * No neoadjuvant chemotherapy * Fit for postoperative radiotherapy. No contraindications to radiotherapy * Signed informed consent Exclusion Criteria: * Concurrent or previous malignancy excluding basal or squamous cell carcinoma of the skin * Previous radiotherapy to the chest wall or regional lymph node areas * Patients with severe non-malignant comorbidity in cardiovascular or respiration system * Patients with medical contraindication for radiotherapy: systemic lupus erythematosus, cirrhosis * pT1-2N1 with none of the following risk factors: \<40 years, Grade 3, lymphovascular invasion positive, ER/PR negative or HER2 overexpression * Patients with supraclavicular or internal mammary nodes metastases * Known definitive clinical or radiologic evidence of metastatic disease * Bilateral breast cancer or historically confirmed contralateral invasive breast cancer * Treated with neoadjuvant chemotherapy * ECOG: 3-4 * Pregnant or lactating * Conditions indicating that the patient cannot go through the radiation therapy or follow up * Unable or unwilling to sign informed consent