METHODS: This is an economic evaluation. We constructed an individual-based Monte Carlo method to simulate with probabilistic sensitivity analysis the development of breast cancer over a woman's lifetime in a hypothetical birth cohort aged 20 years in 2018 (n = 33500) using best available data mainly from government statistics. We predicted the cases of, and deaths due to breast cancer in the base case (with the actual breastfeeding rate in 2018) and two hypothetical optimal scenarios (90% exclusive breastfeeding for six months or cumulative exclusive/partial breastfeeding for at least 12 months). The healthcare cost-savings, the number of deaths averted and the increase in disability-adjusted life years (DALYs) due to the prevention of breast cancer attributed to a higher breastfeeding rate were then deduced, assuming an annual discount rate of 3%.

RESULTS: Increasing the proportion of parous women breastfeeding exclusively for six months from 26 to 90% averted 266 (95% CI 259, 273) or ~ 10% of all-stage breast cancer cases, 18 deaths (95% CI 17, 19) and 399 DALYs (95% CI 381, 416), over the lifetime of each annual cohort of women in Hong Kong. The lifetime medical costs that could be saved would be ~ USD3 million using 2018 prices. However cost-savings were 5-times less in another scenario where the cumulative partial/exclusive breastfeeding for 12 months in parous women is increased to 90% due to its weaker protection against breast cancer compared to exclusive breastfeeding.