For the majority of women with early-stage breast cancer, conservative management with breast conserving surgery plus radiotherapy is widely embraced. However, in patients with germline mutations of BRCA1 and BRCA2, the safety of breast conservation therapy remains controversial. These breast cancer susceptibility genes are associated with an increased risk of second cancers, although the prognosis of BRCA1 or BRCA2 breast cancer is similar to patients with sporadic breast cancer. Preclinical evidence for radiosensitivity has prompted concern for radiation-induced complications in patients with genetic breast cancer. There is limited literature on the safety breast conservation therapy in patients with BRCA1 and BRCA2 mutations. The largest published study reported acute and chronic radiation toxicity results and noted no adverse sequelae in the genetic cohort [1]. Selected published studies demonstrate recurrence rates and overall survival comparable to sporadic controls [1–3]. A series with longer follow-up reported an increase in late second-primary breast cancers, highlighting the need for preventative strategies [4]. Tamoxifen and oophorectomy have a potential role in modifying the rate of second events, and thereby improving the safety of breast conservation therapy.

Tissue-specific stem cells play a key role in organ homoeostasis. They are relatively well characterized in systems which undergo constant proliferation and production of differentiated cells, including the haemopoietic system, skin and intestine. However, little is known about the role and regulation of stem cells in the mammary gland. This review briefly summarizes the current understanding of the role of breast-specific stem cells in normal and cancerous tissues, and how this may identify new targets for breast cancer prevention and therapy.