Health Briefs

July 28, 2002

Breast Cancer: Nature vs. Nurture
At the present time, only two gene mutations (BRCA-1 and BRCA-2) have been identified as risk factors for inheritable breast cancer, and only about 10% of all breast cancer tumors have either of these two gene mutations.  Therefore, it is assumed that families who have multiple close relatives with breast cancer, and who are all free of BRCA mutations, may have as yet undiscovered genetic mutations in play.  A new study in the current issue of the British Journal of Cancer has found evidence, albeit indirectly, of additional inheritable gene mutations in a study of 2310 identical and fraternal (non-identical) twin women.  In this study, fraternal twin sisters of women with breast cancer were found to experience 1.7 times the risk (or a 70% increased risk) of developing breast cancer when compared to a non-twin woman with the same personal and family history risk factors.  When the identical twins were assessed, the twin sisters of women with breast cancer were found to be at 4.4 times the risk of developing breast cancer (or a 340% increased risk).  Using complex statistical calculations to assess potential known and unknown risk factors, the researchers found that the most likely explanation for these findings was the existence of as yet undiscovered breast cancer susceptibility genes. 

As the human genome, or genetic code, is fully unraveled, additional genetic abnormalities that predispose to an increased risk of breast cancer are certain to be found.  Understanding the basis of these genetic predispositions offers the best hope of improved screening, diagnosis and treatment of breast cancer.

Cardiorespiratory Fitness & Inflammation
C-reactive protein (CRP) is a blood marker of inflammation that has been linked to an increased risk of coronary artery disease in a number of research studies.  At the same time, it is well-known that increasing levels of cardiorespiratory fitness are associated with a decrease in the risk of coronary artery disease.  A new study in the journal Circulation has assessed the relationship between these two “heart health” factors for the first time.  A total of 135 women volunteers were assessed for CRP levels in the blood, and for cardiorespiratory fitness through the use of a treadmill exercise test.  This study determined that decreasing levels of aerobic fitness were associated with higher levels of CRP in the blood.  The authors conclude that higher levels of fitness appear to reduce, by some unknown mechanism, the inflammatory changes that increase CRP production.  Thus, this study provides yet more evidence of the pervasive health benefits that arise from regularly engaging in at least moderate exercise!

Kidney Transplants from Cadaver Donors
There are more than 30,000 people in the United States who are currently awaiting the availability of a suitable kidney for transplantation.  Just over 10,000 donor kidneys are matched up each year with people who have suffered the irreversible failure of their own kidneys.  Although hemodialysis can prolong the lives of most people with kidney failure, dialysis cannot replace the function of normal kidneys, and is associated with many serious and even life-threatening complications.  At the present time, donor kidneys are taken from volunteer “living donors” (usually, but not always, a family member), or from brain-dead volunteer donors with still beating hearts.  In the latter case, the kidneys are removed from a person who has no remaining brain function, but whose heart continues to pump blood to the kidneys and other vital organs.  In most cases, brain-dead patients rapidly experience a progressive loss of heart function as well, often within a few hours of losing brain function.  This factor often translates into a very brief window of opportunity during which the donor kidney can be recovered and prepared for transplantation.  After the heart has stopped beating, the kidneys begin to deteriorate due to loss of blood flow, and have generally not been considered transplantable at this stage.  In this week’s issue of the New England Journal of Medicine is a Swiss study that looked at the transplantation of kidneys from donors who had lost all cardiac function as well as brain function.  The authors transplanted 122 kidneys taken from donors with a heartbeat and 122 kidneys from donors without a heartbeat.  They then followed both groups of transplant recipients for 15 years.  Recipients receiving kidneys from donors without a heartbeat experienced a significant delay in the onset of function by the transplanted kidney in 48% of cases, while the kidneys taken from donors with a heartbeat had delayed function in 24% of cases.  However, and most importantly, the long-term rate of kidney transplant survival was essentially equal in both groups of patients: 79% for the kidneys taken from donors without a heartbeat and 77% for the organs taken from donors with a heartbeat.  This is very good news, indeed, as it has the potential to dramatically increase the number of donor kidneys available for transplant each year.  This study, although involving a relatively small number of patients, should have a rapid and dramatic impact on the practice of kidney transplantation.  Various other organs used for transplants have different individual tolerances for the duration of blood flow loss.  Therefore, additional research will be necessary to determine whether or not other commonly transplanted organs, such as the liver, heart, pancreas and intestines, can safely endure brief periods of ischemia (loss of blood flow) and still retain their ability to function following transplantation.

Dr. Robert A. Wascher