Breast Cancer

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Basics

Description

  • Malignant neoplasm of cells native to the breast—epithelial, glandular, or stroma
  • Types: ductal carcinoma in situ (DCIS), infiltrating ductal carcinoma, infiltrating lobular carcinoma, Paget disease, phyllodes tumor, inflammatory breast cancer (BC), angiosarcoma
  • Molecular subtypes: luminal A (HR+/HER2−), triple negative (HR−/HER2−), luminal B (HR+/HER2+), HER2-enriched (HR−/HER2+)

Epidemiology

Incidence
  • Estimated new female BC cases for in situ 63,410; invasive 252,710 in 2017
  • Estimated new male BC cases 2,470
  • Estimated deaths 2017 females 40,610; males 460
  • Most commonly diagnosed cancer (CA) and the second most common cause of CA death for U.S. women

Prevalence
>3.5 million U.S. women with a history of BC were alive on January 1, 2016 (1).

Etiology and Pathophysiology

  • Genes such as BRCA1 and BRCA2 function as tumor suppressor genes, and mutation leads to cell cycle progression and limitations in DNA repair (2).
  • Mutations in estrogen/progesterone induce cyclin D1 and c-Myc expression, leading to cell cycle progression.
  • Additional tumors (33%) may cross talk with estrogen receptors and epidermal growth factors receptors (EGFR), leading to similar abnormal cellular replication.

Genetics
  • Criteria for additional risk evaluation/gene testing in affected individual (2)[A]
    • BC at age ≤50 years
    • BC at any age and ≥1 family member with BC ≤50 years of age or ovarian/fallopian tube/primary peritoneal CA any age or ≥2 family members with BC or pancreatic CA any age or population at increased risk (e.g., Ashkenazi Jew with BC or ovarian CA at any age)
    • Triple-negative BC (ER−, PR−, HER2−)
    • Two BC primaries in single patient
    • Ovarian/fallopian tube/primary peritoneal CA
    • 1+ family member with BC and CA of thyroid, adrenal cortex, endometrium, pancreas, CNS, diffuse gastric, aggressive prostate (Gleason >7), leukemia, lymphoma, sarcoma, dermatologic manifestations, and/or macrocephaly, GI hamartomas
    • Male BC
    • Known BC susceptibility gene mutation in family
  • Criteria for additional risk evaluation/gene testing in unaffected BC individual
    • First- or second-degree relative with BC ≤45 years of age
    • ≥2 breast primaries in one individual or ≥1 ovarian/fallopian tube/primary peritoneal CA from same side of family or ≥2 w/ breast primaries on same side of family
    • 1+ family member with BC and CA of thyroid, adrenal cortex, endometrium, pancreas, CNS, diffuse gastric, aggressive prostate, leukemia, lymphoma, sarcoma, dermatologic manifestations, and/or macrocephaly, GI hamartomas
    • Ashkenazi Jewish with BC/ovary CA at any age
    • Male BC
    • Known BC susceptibility gene mutation in family
  • BRCA1 and BRCA2 are inherited in an autosomal fashion and account for 5–10% of female and 5–20% male CAs; 15–20% familial BCs
    • Mutations higher in Ashkenazi Jewish descent (2%)
    • Mutation in BRCA raises risk to 45–65% from 7% at age 70 years.
  • Other BC associated genes: ATM, BARD1, BRIP, CDH1, PTEN, STK11, CHEK2, p53, ERBB2, DIRAS3, NBN, RAD50, RAD51
  • Syndromes associated with BC: Cowden syndrome (PTEN), Li-Fraumeni syndrome (TP53), ataxia-telangiectasia (ATM), and Peutz-Jeghers (STK11)

Risk Factors

  • Risk calculator: http://www.cancer.gov/bcrisktool/
  • Relative risk (RR) >4.0: age >65 years, biopsy confirmed atypical hyperplasia, BRCA mutation, DCIS, LCIS, personal history of early onset BC (<40 years), two or more first-degree relatives diagnosed at an early age
  • RR 2.1 to 4.0: personal history of BC (40+ years), postmenopausal, radiation history, one first-degree relative of BC
  • RR 1.1 to 2.0: EtOH, Ashkenazi Jewish, DES exposure, early menarche (<12 years), late menopause (>55 years), high socioeconomic status, first pregnancy >30 years, proliferative breast disease without atypia (fibroadenoma or ductal hyperplasia), dense breasts (>50%), never breastfed, no full-term pregnancies, obesity, personal history of endometrial or ovarian CA, HRT long term, recent OCP use, height (tall)
  • 20–25% lifetime risk should receive an annual MRI beginning at age 30 years: BRCA mutation, first-degree relative with BRCA mutation, history of radiation age 10 to 30 years, Li-Fraumeni or Cowden syndrome or first-degree relative with the same
  • 15–20% lifetime risk: personal history of BC, DCIS, LCIS, atypical ductal hyperplasia, atypical lobular hyperplasia, dense or unevenly dense breasts

General Prevention

  • Maintain healthy weight—obesity increases BC risk, physical activity, and healthy diet are key.
  • Limit EtOH—moderate alcohol use increases risk of BC.
  • Breast self-exams (BSE): ACS no longer recommend monthly structured BSE but support self-awareness.
  • Clinical breast exam (CBE):
    • USPSTF: insufficient evidence to assess clinical benefits and harms (3)[A]
    • ACS: no clear benefit or structured guidelines in average-risk women (1)
  • Mammography:
    • USPSTF: women biennial mammogram at age 50 to 74 years (3)[B]
    • ACS: women annual mammograms starting at age 45 years and transition to biennial mammograms at age 55 years (1)

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