Breast cancer tumour board: Which patients are eligible for radiotherapy de-escalation or omission?

Adjuvant radiotherapy after conservative surgery is the standard treatment for invasive breast cancer, showing reduced risk of local recurrence and long-term mortality. However, advances in tumour biology and the emergence of molecular signatures have identified subgroups with a very low risk of recurrence, particularly patients with luminal A cancers, reigniting the debate on potential radiotherapy de-escalation in this population. In addition, achieving a complete pathological response in patients who have received neoadjuvant chemotherapy suggests the possibility of adapting radiotherapy indications. This article aimed to present the major currently available data on the omission of radiotherapy in the treatment of luminal A phenotype breast cancers after conservative surgery, as well as ongoing trials on irradiation de-escalation in cases of complete pathological response after neoadjuvant chemotherapy, particularly for the cN1-ypN0 and cN2-3-ypN0 subtypes. Several prospective studies and randomized trials, including LUMINA, PRIME II, and trials using genomic signatures (POLAR, Oncotype DX®, Prosigna®), suggest the feasibility of omitting radiotherapy for some very low-risk patients, without demonstrated effects on overall survival. However, the persistent benefit of local control has been observed. The National Surgical Adjuvant Breast and Bowel Project (NSABP)-B51/Radiation Therapy Oncology Group (RTOG) 1304 trial and Radiotherapy After Primary Chemotherapy (RAPCHEM) registry showed that the omission of nodal radiotherapy could be considered after a complete nodal pathological response (ypN0), with good short-term locoregional control, although definitive long-term results have not been reported. The omission of radiotherapy for breast cancers with a good prognosis, particularly in patients with luminal A tumours and those with a complete response after neoadjuvant treatment, represents a promising avenue for therapeutic de-escalation. However, it must be determined based on strict biological and clinical selection criteria and validated via long-term controlled trials.