Most 'abnormal' Pap smears won't lead to cancer

LONDON (Reuters Health) - At least 80 percent of women who have worrying evidence of cell abnormalities on a Pap smear will not go on to develop cervical cancer, a new analysis by British researchers suggests.

All of these women will be treated "just in case," meaning that many will undergo further tests and small operations. But cervical cancer treatments are relatively minor, and not too invasive, meaning Pap screening is still worth doing despite these problems, say Dr. Angela E. Raffle and colleagues.

"You can't escape the fact that to be effective in cancer screening you almost have to over-treat because the cell changes and tissue changes are so common," said Raffle, from Avon Health Authority in Bristol.

Her group analyzed screening records from 348,419 women in the Bristol area. They report their findings in Friday's British Medical Journal.

For every 10,000 women screened between 1976 and 1996, 1,564 had abnormal cervical cells detected in the Pap smear. Of those, 818 had further investigations, of whom 543 had evidence of abnormal cervical tissue. Within this group, 176 had abnormalities that persisted for 2 or more years.

Without screening, the researchers say, 80 of these women would be expected to develop cancer by 2011, of whom 25 would die. Screening would avoid 10 of these deaths.

"In the NHS cervical screening programme, around 1,000 women need to be screened for 35 years to prevent one death," they write.

An important implication of their results is the need to help women understand what an abnormal Pap smear really means, the researchers say. While it is important for women to have tests and not to ignore the results, trauma caused by thinking it is something akin to a death sentence is not necessary.

"We really need to change people's perception of what's meant by an abnormal smear," Raffle said.

"Most of these abnormalities are no problem at all, but the treatment's simple and we really think that everyone with a high grade abnormality needs treatment because we know that for one in eighty it will make that big, life-saving difference."

Cervical cancer is ideal for screening, because doctors can get to the cervix without surgery, it can be treated locally, Raffle said. But the same cannot be said of all other cancers.

"I think the real implications for our findings are for prostate cancer, bowel cancer, ovarian cancer -- all these others that people say we must start screening for," the Bristol researcher said.

It is possible that a large proportion of abnormalities detected in those organs will never develop into cancer, but the treatment can be much more damaging than that for cervical cancer -- involving major surgery or radiation treatment.

"Our study points to the potential for harm. It's only minimal harm with the cervix because you're talking about worrying people, but if you're talking about an operation that could leave you dead, or impotent or incontinent, then it's a different equation really," Raffle said.