Inheritance of common cancers

It has taken a star like Angelina Jolie to propel the issue of hereditary cancer into the stratosphere of our consciousness. She decided to undergo removal of both her breasts when it was found that she carries a gene (BRCA) that increases the risk of breast cancer very significantly.

Men having the BRCA2 gene are nearly nine times more likely to develop prostate cancer

We have known for a long time that genes are responsible to a greater or lesser extent for a large number of disorders and that early detection of these hereditary tendencies could lead to measures, however drastic, to reduce the risk.

A woman carrying the BRCA gene is five times more likely than other women to develop breast cancer. In such a case, removal of the breasts reduces the risk of developing cancer by 90 per cent.

However, one must put things into perspective. Most women who develop cancer of the breast do not have this particular gene: only about 10 per cent of women with breast cancer are found to have this gene.

Is there any way of suspecting that one is carrying the abnormal gene? Screening every woman for this particular gene is the only way to find out, but the cost entailed would be prohibitive and the results probably do not justify this extensive exercise.

Women at special risk are more likely to have other members of the family who had the disease. Any woman who has had two close relatives who developed cancer of the breast should be thus investigated, and if found to be a carrier of the gene, should be advised accordingly and given the option of having both breasts removed.

Current research is concentrating on detecting genetic abnormalities that may be used as markers of disease and which can, hopefully, be used to predict who is more likely to develop conditions well before they have become too advanced to treat.

Tumours, like an iceberg, spend most of their time submerged, hidden, undetected, and it may take several years for a tumour to become diagnosed by current diagnostic techniques, however sensitive.

So the search is on. It is interesting to note that a recent extensive study conducted by the Institute of Cancer Research in London involving more than 20,000 men showed that men having the BRCA2 gene are nearly nine times more likely to develop prostate cancer, while those carry-ing the BRCA1 gene have just over a threefold increased risk, compared with those who do not have these genetic abnormalities.

It has now been reported that the first man to undergo prostatectomy when he was found to have the genetic mutation was performed in London by Roger Kirby, an eminent prostate cancer specialist.

In an interview with The Sunday Times of London, Dr Kirby said: “Knowing you are a carrier is like having the sword of Damocles hanging over you. You are living in a state of constant fear.”

Against this approach, one must remember that prostatectomy is not without dangers and drawbacks. One has to be very care-ful when to adopt an aggressive, preventative approach, like prophylactic surgery, where complications can be quite high.

On the other hand, genetic analysis might select those who are more likely to have a particularly aggressive outcome from those others who might be more likely to pursue a more chronic and benign course.

The main factors to make a person suspect he has prostate cancer (the most common tumour in men) are based on symptoms described by the patient, followed by a digital rectal examination, together with the estimation of a prostate tumour marker, and a PSA (prostate-specific antigen).

It is no longer beyond the realm of science fiction to expect that, within the next few years, all of us would have our individual gene map worked out for a reasonable amount of money.

This would enable clinicians to determine what disorders we are most likely to be genetically susceptible to.