Pattern of uptake and excretion of F-18-FDG in the lactating breast

Excretion of radiopharmaceuticals into breast milk poses a potential risk t o infants and clear recommendations regarding interruption times are requir ed. There are few data available regarding the impact of F-18-FDG on this i ssue. With increasing use of PET for oncologic imaging and its potential ad vantages to nursing mothers because of its short physical half-life compare d with other commonly used tumor imaging agents such as Ga-67 and (TI)-T-20 1, evaluation of the excretion pattern of this agent in breast milk is impo rtant. Methods: We have evaluated the uptake of FDG in the breasts in 7 wom en, 6 of whom were lactating and 1 of whom was in early postpartum but had not commenced breast-feeding. Milk samples were obtained from 4 of the lact ating women, including serial samples from 1. Results: Significantly increa sed breast uptake was identified in all lactating breasts but not in 1 brea st consistently refused by the nursing infant or in the woman who had not b egun breastfeeding after delivery of her child. No qualitative change or se miquantitative estimate of radiotracer uptake in the breast was seen after expression of breast milk. Decay-corrected activity measurable in breast mi lk ranged from 5.54 to 19.3 Bq/mL/MBq injected. Using a standard model of b reast-feeding, the calculated maximum cumulative dose to the infant, 0.085 mSv with no interruption of breast-feeding, is well below the recommended l imit of 1 mSv. Conclusion: High uptake of FDG in the lactating breast appea rs to be related to suckling. There is, however, little secretion of activi ty into breast milk. Accordingly, a higher radiation dose is received by th e infant from close contact with the breast than from ingestion of radioact ive milk.