Why good research is crucial

 

It is an accepted principle of medical education that one should try not to be influenced by extreme cases.

But, as human beings, doctors are deeply affected by the awful and the exceptional. Impervious to scientific and educational propriety, such cases burn their way into one's memory.

Whenever cervical cancer is mentioned, "Maria", a 19-year-old patient of mine, comes to mind. As she was an occasional visitor for contraceptive advice, it was unusual to see her one morning complaining of abdominal pain and a vaginal discharge.

Clinical examination revealed nothing untoward, and I sent off a cervical smear to the laboratory that afternoon. About two weeks later, I received a call from the consultant cytopathologist. An analysis of Maria's smear revealed evidence of invasive cancer of the cervix. Worse was to follow. After Maria was seen urgently by a gynaecologist, a biopsy showed a rare aggressive form of cancer, and the specialist was concerned about local spread. It was necessary to remove her entire womb, including the cervix and local lymph nodes. By now it was early summer, and Maria returned home to try to pick up the pieces. She was devastated and, I think, deep down knew her chances of survival were slim. She had to curtail a holiday when she became unwell. Back in hospital, doctors found the cancer was running riot in her body. By September, the poor woman was dead.

Maria's story is truly unusual. I have seen no other case like it. Normally a slow-growing tumour that can be picked up early in its evolution by routine smear testing, hers was a hugely aggressive cervical cancer. Apart from a short time taking the Pill, Maria had no known risk factors. She did not smoke and had few sexual partners. She did not have a sexually transmitted viral infection in the form of the human papilloma virus (HPV). And it was unlikely that her male partner was promiscuous.

But she was on the Pill, which, according to research just published in the Lancet, is associated with an increased risk of cancer of the cervix. It found the level of increased risk was directly linked to how long a woman had been using hormonal contraceptives, such as the commonly prescribed oestrogen and progestogen Pill.

A prestigious group of researchers from the International Agency for Research on Cancer and the Cancer Research UK epidemiology unit at Oxford University combined results from 28 studies to examine the relationship between cervical cancer and hormonal contraceptives. Commissioned by the World Health Organisation, the research was designed to quantify any risk and assess the role of HPV infection.

The results showed that the relative risk of developing cervical cancer increased with the length of time a woman used hormonal contraception. For a woman taking the Pill for more than 10 years, her risk of cancer of the cervix doubled. Even when possible alternative explanations, such as the number of sexual partners, smoking and the use of barrier contraceptives, were excluded, the risk remained constant.

In the 10 studies that looked at women who were positive for HPV and who had cervical cancer, it was found that using the Pill for more than 10 years increased the risk of cancer two and a half times. The authors found no research with which to analyse the risk of taking the progesterone-only, "mini" Pill. For women who used injectable contraception for five years or more, there was only a slight increase in cancer risk, which was of questionable significance.

The same week as the landmark Lancet paper, a group of French doctors writing in the British Medical Journal questioned the current move away from the traditional method of analysing a "pap" smear. Named after Dr George Papanicolaou, a Greek-born US anatomist who in 1943 pointed out that the cervix was an accessible area where cancerous changes in cells could easily be sampled, the traditional slide test is being replaced by a liquid-based technology. The French research, at variance with most previous comparisons, suggests this technique should not replace the tried-and-tested version.

So as one aspect of cervical cancer becomes clearer, another will be reopened to debate. Such is the value of high-quality medical research. No matter how memorable, patient vignettes represent the art rather than the science of medical practice.

You can e-mail Dr Muiris Houston at mhouston@irish-times.ie. He regrets he cannot answer individual queries