The NCCN guidelines state that breastfeeding after childbirth is not contraindicated in breast cancer patients who have undergone breast-conserving surgery. However, the amount of milk produced by breast cancer patients who have undergone breast-conserving surgery may be insufficient, and the milk may lack some essential nutrients. Breastfeeding is not recommended while the patient is undergoing active anti-tumor therapy (e.g., chemotherapy, endocrine therapy).