Epidemiology of breast cancer
Epidemiology
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In U.S., most common cancer in women; 2nd leading cause of cancer death in women
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Genetic risk: 15–20% ⊕ FHx → 2× ↑ risk; ~45% familial cases a/w germline mutation. BRCA1/2: 35–85% lifetime risk of breast ca. Germline loss-of-function mutations in PALB2 a/w 35% ↑ risk breast cancer by age 70. Moderate risk mutations CHEK2 and BARD1 a/w 15–30% lifetime risk of breast cancer (NEJM 2021;384:428).
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Estrogen: ↑ risk with early menarche, late menopause, late parity or nulliparity (NEJM 2006;354:270); ↑ risk with prolonged HRT (RR = 1.24 after 5.6 y; JAMA 2003;289:3243); OCP use a/w extremely low to no ↑ risk (NEJM 2017:317:2228; JAMA Oncol 2018;4:516)
- Benign breast conditions: ↑ risk if atypia (atypical ductal or lobular hyperplasia; NEJM 2015;372:78) or proliferative (ductal hyperplasia, papilloma, radial scar, or sclerosing adenosis) features; no ↑ risk w/ cysts, simple fibroadenoma, or columnar changes
- ↑ risk with h/o ionizing radiation to chest for treatment of Hodgkin lymphoma