Cervical cancer vaccine

Medical Matters:This being European cervical cancer prevention week, it reminds me that the most aggressive cancer I have seen in practice involved Sharon, a young woman of 20 who presented with abnormal vaginal bleeding.

An internal examination revealed a growth on the cervix (the neck of the womb) and so she was urgently referred to see a gynaecologist.

Unfortunately, a biopsy confirmed my worst fears; Sharon had cancer of the cervix which, despite the brevity of her symptoms, had spread into the womb itself. And even though she underwent surgery and radiotherapy, three months later she was dead.

I should emphasise that this was an extremely unusual case of cervical cancer.

Rare in the under-25s, the peak incidence of cancer of the neck of the womb is 45-50 years of age; in the majority of cases it takes 10 years to develop.

Cervical cancer is also unique in that it can be identified at a pre-invasive stage. This is the basis of cervical screening programmes, in which a smear of cells taken from the cervix is examined under a microscope by a skilled technician.

Changes in the cells are called cervical intra-epithelial neoplasia (CIN), of which there are three stages. While about 60 per cent of low-grade lesions (CIN1) will spontaneously return to normal, the majority of those in the CIN3 category will progress slowly to full-blown cancer. CIN2 and 3 lesions are referred for colposcopy, an outpatient procedure involving a closer look at the cervix and a possible tissue biopsy.

On average, some 180 new cases of cervical cancer are diagnosed in the Republic annually. Just over 70 women die from the disease here every year. At present only 9 per cent of the population (those living in the midwest) are systematically screened, although a rollout of a national cervical cancer screening programme has been promised.

One of the principal causes of cervical cancer is persistent infection with the human papilloma virus (HPV).

Infection occurs soon after a person becomes sexually active. There are over 80 HPV subtypes, most of which do not cause cancer. But types 16 and 18 are thought to cause 70 per cent of cervical cancers, with another five subtypes responsible for a further 20 per cent of cases.

It is estimated that 10 per cent of women infected with a cancer-causing HPV will develop pre-cancerous changes in the cervix.

Recent advances in HPV testing and the development of two vaccines to prevent infection with the virus has led to a re-examination of methods used to prevent cancer of the cervix.

Sanofi Pasteur/MSD has launched Gardasil, the first vaccine against HPV. GlaxoSmithKline is expected to get approval for its vaccine, Cervarix, later this year. Both vaccines aim to prevent cervical cancer; in addition Gardasil is active against those HPV subtypes known to cause genital warts.

Both products involve a three vaccine course, given over a six-month period. And clinical trials involving a two-year follow-up have shown that both vaccines are 100 per cent effective in preventing HPV infection and cancer.

However, a 10-year follow-up is needed before it can be absolutely said that HPV vaccine prevents cervical cancer.

HPV vaccines must be given before infection with the virus occurs. This means administering the course prior to the person becoming sexually active. Gardasil has been given a licence for those from aged nine to 26; a comprehensive vaccination programme would need to be administered to girls in the 11-13 year age bracket.

This may prove controversial. So far, the national immunisation advisory committee has not indicated whether it will recommend a population-based immunisation programme with HPV vaccine.

It will have to consider whether some parents may be concerned that the jabs will encourage unprotected sex and send out confused messages as to the appropriate age at which to become sexually active.

The committee will also have to look at the issue of cost - Gardasil costs about €120 per shot wholesale and is not available under the medical card scheme.

The US state of Michigan has made HPV vaccination compulsory for girls entering sixth grade in school. The UK department of health is said to be looking positively at the idea of a state- funded programme.

But already pressure groups in both the US and Britain, representing those of a conservative religious disposition, have questioned whether 12 years of age is too young for cervical cancer immunisation.

However, with 100 per cent efficacy and the prospect of eradicating 70 per cent of cervical cancers over time, there is compelling scientific evidence for the vaccine's introduction.

Women now have an opportunity to protect themselves against the second most common form of female cancer.

It's now up to the national immunisation advisory committee to ensure that cervical cancer vaccine is available to all young women in the Republic free.

Dr Muiris Houston is pleased to hear from readers at mhouston@irish-times.ie but regrets that he cannot answer individual queries.