Several trials evaluated the omission of radiation therapy (RT) for low-risk early stage breast cancer patients. In interpreting the results, we should mind its generalizability because a disproportionately high very low risk population was recruited and because of the uncertain benefit from endocrine therapy for these patients. As both endocrine treatment and RT have no demonstrated clinically relevant survival benefit in low-risk patients, and as withholding both treatments together is associated with a high local-recurrence risk, the burden and side effects of both treatments should be used to select one of both treatment options, taking into account comorbidities, life expectancy and personal preferences.
Apart from complete omission of RT, several ways to tailor its extent include lowering the total dose, such as selective omission of the boost in the framework of breast-conserving therapy, hypofractionated RT to shorten the duration of treatment and (accelerated) partial breast irradiation for selected patients with early stage BC.
Substitution of surgery:
In general, the use of RT compensates for the decreasing extent of surgery to the breast and the axillary lymph nodes, eliminating residual tumour cells while maintaining better aesthetic and functional results. With the gradual shift for the timing of the sentinel node procedure from before to after PST, completion axillary surgery becomes more reserved for cases with residual macroscopical involvement while all other cases are offered regional nodal RT, especially after the demonstration of its benefits on local-regional control, disease-free survival, breast cancer mortality and overall survival in randomised trials and meta-analyses.
Escalation:
The demonstration of the impact of regional nodal RT on disease-related outcome in particular by a reduction in distant metastases led to its increased popularity. Further research is on-going to evaluate RT after primary systemic treatment.