title: Serum lipids, lipoproteins, and risk of breast cancer: a nested case-control study using multiple time points.
abstract: BACKGROUND
  There is strong evidence that breast cancer risk is influenced by environmental factors. Blood lipid and lipoprotein levels are also influenced by environmental factors and are associated with some breast cancer risk factors. We examined whether serial measures of serum lipids and lipoproteins were associated with breast cancer risk.
  
  
  METHODS
  We carried out a nested case-control study within a randomized long-term dietary intervention trial with 4690 women with extensive mammographic density followed for an average of 10 years for breast cancer incidence. We measured lipids in an average of 4.2 blood samples for 279 invasive breast cancer case subjects and 558 matched control subjects. We calculated subaverages of lipids for each subject based on menopausal status and use of hormone replacement therapy (HRT) at blood collection and analyzed their association with breast cancer using generalized estimating equations. All statistical tests were two-sided.
  
  
  RESULTS
  High-density lipoprotein-cholesterol (HDL-C) (P = .05) and apoA1 (P = .02) levels were positively associated with breast cancer risk (75(th) vs 25(th) percentile: HDL-C, 23% higher; apoA1, 28% higher) and non-HDL-C (P = .03) and apoB (P = .01) levels were negatively associated (75(th) vs 25(th) percentile: non-HDL-C, 19% lower; apoB, 22% lower). These associations were observed only when lipids were measured when HRT was not used. Total cholesterol and triglyceride levels were not statistically significantly associated with breast cancer risk.
  
  
  CONCLUSIONS
  These results demonstrate that serum lipids are associated with breast cancer risk in women with extensive mammographic density. The possibility that interventions for heart disease prevention, which aim to reduce non-HDL-C or raise HDL-C, may have effects on breast cancer risk merits examination.
authors: Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, Ontario, Canada (LJM, OM, EH, CVG, SM, NFB); Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (PWC); Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada (PWC).
authors: Lisa J
authors: LJ
authors: Martin
authors: Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, Ontario, Canada (LJM, OM, EH, CVG, SM, NFB); Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (PWC); Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada (PWC).
authors: Olga
authors: O
authors: Melnichouk
authors: Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, Ontario, Canada (LJM, OM, EH, CVG, SM, NFB); Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (PWC); Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada (PWC).
authors: Ella
authors: E
authors: Huszti
authors: Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, Ontario, Canada (LJM, OM, EH, CVG, SM, NFB); Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (PWC); Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada (PWC).
authors: Philip W
authors: PW
authors: Connelly
authors: Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, Ontario, Canada (LJM, OM, EH, CVG, SM, NFB); Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (PWC); Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada (PWC).
authors: Carolyn V
authors: CV
authors: Greenberg
authors: Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, Ontario, Canada (LJM, OM, EH, CVG, SM, NFB); Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (PWC); Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada (PWC).
authors: Salomon
authors: S
authors: Minkin
authors: Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, Ontario, Canada (LJM, OM, EH, CVG, SM, NFB); Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, Ontario, Canada (PWC); Departments of Medicine and Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada (PWC). boyd@uhnres.utoronto.ca.
authors: Norman F
authors: NF
authors: Boyd
mesh_terms: D000328:Adult; D000368:Aged; D016632:Apolipoprotein A-I / Q000097:blood*; D053299:Apolipoprotein B-100 / Q000097:blood*; D001940:Breast / Q000473:pathology*; D000071060:Breast Density; D001943:Breast Neoplasms / Q000097:blood* / Q000453:epidemiology* / Q000473:pathology; D002170:Canada; D016022:Case-Control Studies; D008076:Cholesterol, HDL / Q000097:blood*; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000002:abnormalities; D008593:Menopause; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D014280:Triglycerides / Q000097:blood*
chemical_list: C505693:APOA1 protein, human; C569471:APOB protein, human; D016632:Apolipoprotein A-I; D053299:Apolipoprotein B-100; D008076:Cholesterol, HDL; D014280:Triglycerides