Jewish World Review Sept. 20, 2002 / 14 Tishrei, 5763

Breast Tissue Density & Inheritance

By Robert A. Wascher, M.D., F.A.C.S. | Women with extremely dense breast tissue, as determined by mammography, are at increased risk of developing breast cancer. In this week's New England Journal of Medicine is a study of breast tissue density among pairs of adult monozygotic (identical) twin women and dizygotic (non-identical or fraternal) twin women. A total of 571 pairs of monozygotic twins and 380 pairs of dizygotic twins from Australia, Canada and the United States were enrolled in the study. All study participants underwent digital mammograms, and the resulting x-rays were reviewed by a radiologist who was blinded as to the identity of each patient.

When the resulting data was analyzed, the authors determined that genetic factors accounted for 60 percent of breast tissue density characteristics among the Australian twins, 67 percent of the breast tissue density variability among the North American twins, and 63 percent for all twins studied. This study, therefore, suggests that perhaps as much as 60 percent of the person-to-person variability in breast tissue density is the result of inheritable genetic factors.

As the incidence of breast cancer appears to be higher in women with denser breasts, it will be interesting to see if future studies are able to find a correlation between the as yet undiscovered genes that control breast tissue density and the increased breast cancer risk associated with dense breasts. Unfortunately, this study did not assess the incidence of breast cancer in either the identical or non-identical pairs of twins. Such a study, employing the same comparative analysis of identical vs. non-identical twins would be a logical next step.


The BRCA1 gene mutation has been linked with a significantly increased risk of breast and ovarian cancer. Two studies related to the BRCA1 gene mutation are featured in the current issue of the Journal of the National Cancer Institute. The first study, from England, looked at the incidence of cancers other than breast or ovarian cancer in men and women carrying this particular gene mutation. A total of 11,847 individuals from 699 families with the mutated gene were studied in 30 different centers across Europe and North America.

The authors determined that the BRCA1 gene was associated with a more than two-fold incidence of pancreatic cancer, and a nearly three-fold increase in the incidence of cervical cancer. Among study participants less than 65 years old, there was a nearly two-fold increase in the risk of prostate cancer, although this prostate cancer risk increase was not seen in patients older than 65 years. When the researchers looked at the effect of gender on cancer risks, they found that, overall, women experienced a greater than two-fold increase in the risk of cancers of organs other than the breast or ovary due to the presence of the BRCA1 gene mutation.

However, men did not experience any overall significantly increased risk of such cancers. This study points to the widespread cancer-inducing effects of the mutated BRCA1 gene on multiple organs in the body, in addition to the previously known increased risk of breast and ovarian cancer associated with this mutation.

A second study in the Journal of the National Cancer Institute looks at BRCA1-associated increases in the risks of breast and ovarian cancer associated with the BRCA1. The actual increase in the risk of breast and ovarian cancer caused by the BRCA1 gene mutation has been hotly debated for several years now. This study evaluated 483 BRCA1 gene carriers from 147 affected families. The authors found that the BRCA1 gene conferred a 73 percent likelihood of breast cancer by age 70, and a 41 percent risk of ovarian cancer by age 70. The risk of developing a second breast cancer (i.e., following diagnosis and treatment of an initial breast cancer) was about 41 percent.

Other cancers were found to be more common among patients with the BRCA1 mutation, including a three-fold increase in the risk of pancreatic cancer, a two-fold increase in the risk of colon cancer, a four-fold increase in the risk of stomach cancer, and a 120-fold increase in the risk of fallopian tube cancer.

These two studies, when taken together, greatly add to our understanding of the extent of the BRCA1 gene's impact on cancer incidence among people who carry this mutation. Further study of the mechanisms that underlie this mutated gene's cancer-causing effects is imperative in order to develop effective strategies to blunt the mutation's adverse health effects.


A study in the current issue of the Annals of Internal Medicine looks at the impact of smoking vs. smoking cessation following heart attack, and the risk of recurrent heart attacks. A total of 2,619 patients experiencing their first heart attack were enrolled into this study, and were followed between 1986 and 1996. At the time of the initial heart attack, 34 percent of patients were nonsmokers, 36 percent were former smokers, and 31 percent were active smokers. Among the 808 patients who were active smokers at the time of their initial heart attack, 449 quit tobacco following their heart attack.

When comparing the group of nonsmokers with the patients who quit smoking before their first heart attack, the risk of recurrent heart attack was 17 percent greater among the prior smokers. The patients who had smoked up until their initial heart attack, and who subsequently quit, had a 51 percent greater chance of experiencing recurrent heart attacks than the patients who never smoked.

Among the patients who quit smoking after their first heart attack, the risk of recurrent heart attack was increased by 62 percent during the first 6 months of smoking cessation. This relative risk declined to 48 percent with smoking abstinence between 6 and 18 months, and to only 2 percent after 36 or more months of smoking cessation. Thus, patients who smoke up to-or after-the point at which they experience their first heart attack appear to have a significantly increased risk of a second heart attack when compared to nonsmokers.

However, if smoking is discontinued after the initial heart attack for at least 36 months, then the risk of a second attack falls to approximately the same level as for people who never smoked. Remember, smoking significantly increases not only the incidence of recurrent heart attacks, but also that of first heart attacks as well!


The vitamin folate has previously been linked with a possible reduction in the risk of colorectal cancer. A new study from The Netherlands, as reported in the current journal Cancer, prospectively studied 120,852 men and women aged 55 to 69 years over a period of more than 7 years. Colon cancer occurred in 760 of the research subjects, while another 411 patients developed rectal carcinoma.

The entire group was prospectively assessed for the quantity of folate in their diet. The study concluded that high levels of folate in the diet yielded a 27 percent reduction in colon cancer rates among men, and a 32 percent reduction in women. Regarding the effects of dietary folate on the risk of rectal cancer, high levels of folate in the diet reduced rectal cancer risks by 34 percent in men. Curiously, folate did not appear to provide any significant protective effect associated with the risk of rectal cancer in women.

This study adds to the growing evidence that ample folate levels in the diet may be associated with a reduced risk of developing colon cancer. The apparent gender-related difference in the putative protective effect of folate against rectal cancer is, however, puzzling and suspicious. Additional studies must, therefore, be done to clarify this incongruous finding.

JWR contributor Dr. Robert A. Wascher is a senior research fellow in molecular & surgical oncology at the John Wayne Cancer Institute in Santa Monica, CA. Comment by clicking here.


09/13/02:Dairy Products, Calcium, Vitamin D & the Risk of Breast Cancer; Efficacy of Nonprescription Smoking Cessation Aids; A Nutty Approach to Heart Disease Prevention; Update on Prostate Cancer

09/06/02: C-Reactive Protein & Estrogen Replacement Therapy; Walking Women & Cardiovascular Disease; Physical Activity Among Teenaged Girls

08/30/02: Babbling babies & brain function; homocysteine levels, vitamins & coronary artery disease; St. John's Wort & chemotherapy

08/16/02: A New Weapon Against Anthrax?; cataracts & motor vehicle accidents; gingko biloba takes a hit; air pollution & heart function during exercise; breast cancer genes & the estimated risk of breast cancer

08/09/02: Botulinum Toxin & Post-Stroke Spasticity; Intestinal Hormone Kills Appetite; Bone Marrow Cells Improve Blood Flow in Vascular Disease; Effectiveness of Restraining Orders on Domestic Violence

08/02/02: Mammography Saves Lives!; Obesity & the Risk of Heart Failure; High Sugar Diets & the Risk of Colon Cancer; Abuse During Childhood & Possible Effects of Genes on Antisocial Behaviors

07/26/02: Cancer: Nature vs. Nurture; Cardiorespiratory Fitness & Inflammation; Kidney Transplants from Cadaver Donors; Aircraft Cabin Air Recirculation & the Common Cold

07/19/02: PCBs & the Gender of Babies; Breastfeeding & the Risk of Breast Cancer; More Bad News About Hormone replacement Therapy

07/12/02: A cancer surgeon's perspective on hormone replacement therapy

07/08/02: Hormone replacement therapy & the risk of disease; more good news about statins; antioxidant vitamins & disease prevention; more

06/28/02: Antioxidants & the Risk of Alzheimer's Disease; Effects of Exercise on the Hearts of Patients with Mild Hypertension; Statins reduce cardiac events following angioplasty; more

06/21/02: Sex & violence and Advertising: Do Advertisers Get What they Pay For?; Don't Drink the Water (or the Salsa Either!); Vasectomy & Prostate Cancer Risk; Update on Smoking & Disease

06/14/02: Young Men, Obesity & Heart Disease; Breastfeeding & Obesity; Irritable Bowel Syndrome & rectal pain threshold; more data on cox-2 inhibitors & cancer; more

06/07/02: New coronary artery stent reduces risk of restenosis; possible cause of Parkinson's Disease identified; more

05/31/02: New biological insights into obesity & weight loss; broccoli kills cancer-causing stomach bug; anti-inflammatory drugs and the risk of heart attack

05/24/02: Molecular detection of tumor cells in the blood & prognosis; Cox-2 & breast/lung cancers; BRCA2 gene mutations & the risk of breast cancer; breast density & the risk of breast cancer

05/19/02: Moderate alcohol intake and blood sugar levels; more good news for tea drinkers; blood potassium levels & the risk of cardiovascular disease; ethnic differences in diabetic complications

05/10/02: Tea drinkers and the risk of death following heart attack; duration of breastfeeding & adult intelligence; abdominal aortic aneurysms: surgery or observation?

05/03/02: Risk of adverse drug reactions from newly released medications; preoperative beta-blockers may reduce heart bypass deaths; shape-shifting plastics may alter surgical practice; weight loss supplement may cause liver damage
04/26/02: Angry young men & risk of premature cardiovascular disease; stay-at-home dads & risk of cardiovascular disease; more on the effects of statins; dairy consumption and the risk of pre-diabetes; smallpox vaccine: good to the last drop?
04/19/02: Change your sex by drinking water?; Anti-inflammatory RXs may reduce growth of breast cancer cells; radiation treatment reduces repeat narrowing of bypass grafts
04/05/02: Fish & Omega-3 fatty acid consumption and cardiac health; news briefs
04/05/02: Can coffee reduce your risk of tooth decay?; exercise & blood pressure; a single high-fat meal reduces coronary artery function
04/01/02: Pre-diabetes: a newly defined category of health risk; teen television viewing and subsequent aggressive behavior; the benefits of strength training in the elderly; more ...
03/22/02: Bacteria, antibiotics & heart disease; mammograms: the debate continues; calcium & the risk of colon cancer ... and more
03/15/02: Mammography debate continues; statins & fracture risk; physical fitness & the risk of death; other intriguing findings
03/08/02: Blows to the chest & sudden cardiac death; air quality & the risk of lung cancer; tomatoes and your prostate
03/01/02: Diet & the risk of ovarian cancer; lifetime risk of developing high blood pressure; Osteoporosis prevention with a once-a-year injection?
02/26/02: The continuing controversy regarding screening mammography
02/22/02: Lowering body temperature after heart attack improves outcome; A silver lining for the chronically sleep-deprived?
02/15/02: Hormone replacement therapy & the risk of breast cancer; use it or lose it: Alzheimer's disease & cognitive stimulation; stress, divorce & death; child daycare, infections & parental guilt
02/08/02: Possible breakthrough in early cancer diagnosis; mammography: the controversy continues; CPR techniques revisited
02/01/02: Antibiotics in livestock feed & human disease; genetic detection of early colon cancer in the stool; genetic analysis of breast cancers may help decide treatment
01/25/02: Drug increases lifespan (if you're a fly...); workplace attitudes and smoking cessation; effects of inadequate sleep on surgeons
01/18/02: Lifelong effects of premature birth; smokers under the knife; aspirin and cardiovascular health
01/11/02: Estrogen levels in the blood & breast cancer risk; Heart attack: sex and survival; dangerous lettuce invaders
01/09/02: Cancer & aging: Two sides of the same coin?
01/04/02: Vitamin a & the risk of hip fracture in postmenopausal women; ovarian cancer risk and oral contraceptives
12/28/01: Magnetic Resonance Imaging (MRI) detects coronary artery disease; new development in obesity research; adverse childhood experiences & the risk of suicide attempts
12/21/01: Vaccination of children controls hepatitis a in the community; a possible cure for sickle cell disease; leptin and the risk of heart attacks
12/14/01: Chernobyl and the Risk of Thyroid Cancer in hildren; children & obesity; gastroesophageal reflux disease update
12/07/01: Update on school shootings; new implantable heart-assist device approved for further evaluation; prevention of fungal infections in pre-term babies
11/30/01: Flu vaccination in asthmatics; low-tar cigarettes are not less harmful; beans and your heart
11/21/01: Modified smallpox vaccine may reduce risk of cervical cancer; New approach to breast cancer diagnosis; New non-invasive prenatal diagnostic test for down's syndrome
11/16/01: Cholesterol-lowering drugs reduce risk of heart attack; supplemental radiation therapy reduces risk of breast cancer recurrence; brains of women may answer age-old questions
11/09/01: Bio-warfare (redux); my gray matter is bigger than yours; mad elk disease?
11/02/01: Making sense of bio-warfare
10/26/01: The impact of mammography on deaths due to breast cancer; diet & exercise may slow cancer cell growth; antidepressants and the risk of heart disease
10/19/01: New insights into autism; the wiley appendix
10/12/01: More bad news about obesity links to other diseases…Hey dad, can I borrow the car keys?
10/05/01: California leads nation in reduction of tobacco-related disease; exercise as an antidepressant?
09/25/01: Advances in the detection of breast cancer; primary care physician awareness of peripheral arterial disease; arsenic in the water
09/17/01: In perspective
09/12/01: Genes may hold secret to long life; men and women: cognitive function in the elderly; physical activity, obesity and the risk of pancreatic cancer
09/05/01: English milk cows prefer Beethoven and Simon & Garfunkel over Bananarama; new prostate cancer prevention study: looking for a few good men; exercise & diet can help prevent diabetes
08/28/01: Arthritis drugs may be linked with increased risk of heart disease; errors in blood clotting tests can be fatal; infant soy formula not associated with reproductive side effects

© 2002, Dr. Robert A. Wascher