"Key Points

Question  Does breast cancer risk differ by content of hormonal contraceptives?

Findings  In this cohort study of more than 2 million adolescent girls and premenopausal women in Sweden, breast cancer risk varied by hormone formulation in hormonal contraceptives. Oral formulations containing desogestrel were associated with a higher number of additional cases per 100 000 person-years compared to those containing levonorgestrel.

Meaning  These findings suggest that individuals at risk of breast cancer may benefit from avoiding desogestrel-containing hormonal contraceptives, particularly in progestin-only formulations."