title: Medical radiation exposure and breast cancer risk: findings from the Breast Cancer Family Registry.
abstract: Moderate to high-dose radiotherapy is known to increase the risk of breast cancer. Uncertainties remain about the effects of low-dose chest X-rays, particularly in individuals at increased genetic risk. We analyzed case-control data from the Breast Cancer Family Registry. Self-reported data on therapeutic and diagnostic radiation exposures to the chest were available for 2,254 breast cancer cases and 3,431 controls (1,556 unaffected sisters and 1,875 unrelated population controls). We used unconditional logistic regression analyses to estimate odds ratios (OR) and 95% confidence intervals (CI) associated with radiation exposure, after adjusting for age, study center, country of birth, and education. Increased risks for breast cancer were found for women who had radiotherapy for a previous cancer (OR=3.55, CI=1.47-8.54) and diagnostic chest X-rays for tuberculosis (OR=2.49, CI=1.82-3.40) or pneumonia (OR=2.19, CI=1.38-3.47). Risks were highest for women with a large number of exposures at a young age or exposed in earlier calendar years. There was no evidence of increased risk associated with other diagnostic chest X-rays (not including tuberculosis or pneumonia), both in women with and without indicators of increased genetic risk (i.e., diagnosed at age <40 years or family history of breast cancer). Given the widespread and increasing use of medical diagnostic radiation, continued surveillance of breast cancer risk is warranted, particularly in women at specific genetic risk, such as those carrying mutations in BRCA1 or BRCA2.
authors: Northern California Cancer Center, Fremont, CA 94538, USA. ejohn@nccc.org
authors: Esther M
authors: EM
authors: John
authors: Amanda I
authors: AI
authors: Phipps
authors: Julia A
authors: JA
authors: Knight
authors: Roger L
authors: RL
authors: Milne
authors: Gillian S
authors: GS
authors: Dite
authors: John L
authors: JL
authors: Hopper
authors: Irene L
authors: IL
authors: Andrulis
authors: Melissa
authors: M
authors: Southey
authors: Graham G
authors: GG
authors: Giles
authors: Dee W
authors: DW
authors: West
authors: Alice S
authors: AS
authors: Whittemore
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001315:Australia / Q000453:epidemiology; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D005192:Family Health; D005260:Female; D006801:Humans; D016015:Logistic Models; D008400:Mass Chest X-Ray / Q000009:adverse effects; D008875:Middle Aged; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology*; D016017:Odds Ratio; D011878:Radiotherapy / Q000009:adverse effects; D012042:Registries / Q000706:statistics & numerical data; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013997:Time Factors