Do we need to irradiate all small invasive breast cancers and DCIS?

Breast radiotherapy after lumpectomy is considered standard for nearly all patients with invasive breast cancer and is recommended for many patients after lumpectomy for ductal carcinoma in situ (DCIS). However, there is recognition that lumpectomy alone can achieve optimal cancer control for some patients with invasive breast cancer and DCIS. Patients with breast cancers with lower risk of recurrence are less likely to derive benefit from breast radiotherapy. This review will focus on defining populations of patients with invasive breast cancer and DCIS with a low risk of recurrence post-lumpectomy and the evidence supporting omission of breast radiotherapy post-lumpectomy.