There are risks as well as benefits – so get the facts, then decide

THE past couple of weeks have been good for cervical cancer screening. It is unfortunate it has taken a high-profile figure to develop terminal illness to raise awareness of cervical cancer, however, many health professionals are murmuring that Jade Goody's illness – terrible though it is – may lead to some good.

The uptake of the cervical smear test has increased dramatically since Jade's diagnosis was made public. There is nothing like the illness of a celebrity, especially a personable one, to make people aware of their own mortality.

However, many women undergoing cervical screening don't fully understand the risks and benefits. Jade Goody has helped them to realise cervical cancer is "a bad thing" and there is an understanding that screening is "a good thing". But how screening is good remains a bit of a mystery.

Everything we do in life has risks and benefits, and nowhere is this truer than in healthcare. Cervical screening carries a risk of discomfort and the worry that a positive test brings, but the real benefit of the three-yearly screening programme is that it actually prevents cancer. It usually detects changes in the cervix that precede cancer, allowing treatment (often just a minor operation) and "cure" before cancer has developed. This prevention is why cervical screening is the best sort of screening programme; it is much easier to prevent cancer than to embark on damage limitation when it has already become established.

Unfortunately, many other screening programmes don't prevent cancer; they just detect it in the early stages. Once cancer is detected, the damage limitation starts. This is not to say that some of the detected cancers aren't curable, but they are much more difficult to cure at this stage. The cure rate is also lower once the cancer has developed, and the treatment – surgery, chemotherapy and radiotherapy – is never pleasant.

An article in the British Medical Journal this week has criticised the UK breast screening programme, which aims to detect breast cancer by mammography (basically, taking an X-ray of the breasts). This can detect only properly developed cancers – which is why the benefits of the breast screening programme are much lower than those in cervical screening.

If a breast cancer is detected, treating it is not a small procedure, and the surgery, chemotherapy and radiotherapy offered to women also entails risk. Therefore, breast screening brings greater risks and smaller benefits than cervical screening. It is for these reasons that healthcare professionals have even more of a duty to outline just what the risks and benefits are to the patient.

However, this is not always easy. I remember being given five minutes to explain a screening programme to a patient in my medical final exam. After my brain had gone into meltdown and my mouth into overdrive, I was ushered out of the room, with the examiner telling me I was confusing the patient.

The examiner was right to be brusque. Patients want to make an informed choice, but trying to get the correct balance between too little information, which leaves people feeling they haven't been given any choice, and too much, which leaves people confused, is a difficult skill to master.

Peter Gotzsche and colleagues in the British Medical Journal believe women in the UK are not given the correct information on which to base a decision about breast screening. They think the UK breast screening leaflet – Breast screening: the facts – is too paternalistic. It seems to be written with the premise that breast screening is good, which concurs with many women's fear that breast cancer is bad. However, the leaflet doesn't give adequate information on the risks of screening.

Sometimes, screening produces a false positive, and a woman will be diagnosed with breast cancer when none is present. This is a genuine mistake; no screening programme gets the diagnosis correct 100 per cent of the time.

However, Gotzsche argues that women are not given enough warning about the possibility of this false diagnosis. The NHS leaflet contains only one small paragraph outlining that sometimes false diagnoses occur. The leaflet states that some women have to undergo more "tests" before breast cancer is excluded. However, it does not state that some of these "tests" involve biopsy, surgical removal or radiotherapy of harmless lumps that would not have been detected without screening. In fact, over a ten-year period, 50 per cent of all breast screenings may have a harmless abnormality detected. Given the number of women that undergo screening, over ten years, 50 per cent amounts to a lot of very worried women.

Gotzsche states that if 2,000 women are screened regularly for ten years, only one will be prevented from dying of breast cancer. However, ten women will be treated for cancer that they don't have, and a further 200 will suffer the worry of being falsely diagnosed with cancer.

Women need these facts explained to them before they can make a choice about whether to have screening. Only they can decide whether they think the possibility of having a mastectomy, chemotherapy or radiotherapy for a "cancer" that is not really present is outweighed by the much smaller possibility that if a true cancer is present, early treatment may save their lives.

Like all illnesses, cancer is unpleasant. However, it is a disease to which people seem to be especially afraid of succumbing. Celebrities who suffer from cancer bring this fear to the fore of many people's minds. But this fear should not lead to irrational decisions on whether to enter a screening programme if healthcare professionals are honest enough with their patients.

Justine Davies is a doctor and medical journalist.