Radiotherapy to the chest wall following mastectomy for node-negative breast cancer: A systematic review

Background. Although nodal status is the major determinant of risk of locoregional relapse (LRR), other factors also contribute, and these assume a greater significance for those with node-negative breast cancer. Previous reviews of post-mastectomy radiotherapy have included studies using radiotherapy techniques or doses no longer considered clinically appropriate. Objectives. To determine the effectiveness of post-mastectomy radiotherapy in women with node-negative breast cancer with particular reference to those patient and tumour factors which contribute to an increased risk of LRR. Methods. A systematic literature review was conducted. Trials using inadequate or orthovoltage radiotherapy were excluded. Data linking potential risk factors, either individually or in combination, to the occurrence of LRR were handled qualitatively. Data from randomised trials of post-mastectomy radiotherapy were included in a meta-analysis. Results. Baseline risk of LRR is increased in the presence of lymphovascular invasion, a grade 3 tumour, tumours greater than 2 cm or a close resection margin and in patients who are pre-menopausal or aged less than 50. Those with no risk factors have a baseline risk of LRR of approximately 5% or less rising to a risk of 15% or more for those with two or more risk factors. In the meta-analysis of three randomised trials of mastectomy and axillary clearance (667 patients), the addition of radiotherapy resulted in an 83% reduction in the risk of LRR (P < 0.00001) and in a 14% improvement in survival (P = 0.16). Conclusion. The use of post-mastectomy radiotherapy for women with node-negative breast cancer requires re-evaluation. Radiotherapy should be considered for those with two or more risk factors.