Cer­vi­cal cancer screen­ing: the facts

To pre­vent fur­ther tragedy, we need to un­der­stand how the sys­tem failed so we can make in­formed de­ci­sions

The Irish Times - Tuesday - Health - - Front Page - Su­san Smith

Screen­ing for cer­vi­cal cancer is a com­plex area and the Scally re­port (Dr Gabriel Scally’s Scop­ing In­quiry was pub­lished in Septem­ber) highlights these dif­fi­cul­ties and how the Cer­vi­calCheck sys­tem has let down women and their fam­i­lies.

I am a GP, and I have won­dered how this could have hap­pened. There is a sense that doc­tors and nurses trusted a sys­tem and per­haps didn’t al­ways com­mu­ni­cate the com­plex­i­ties in­volved as well as we should have.

As we move for­ward, we need to know the facts so we can make de­ci­sions about screen­ing. I wanted to try and un­der­stand what has hap­pened so I could in­form my pa­tients prop­erly.

I used avail­able Ir­ish data and con­sulted with other GPs and health econ­o­mists in Hiqa, but I take re­spon­si­bil­ity for the sum­mary I pre­sent here.

Cer­vi­cal cancer is the eighth com­mon­est cancer in Ire­land. On av­er­age, each year, there are 277 cases of cer­vi­cal cancer re­sult­ing in 88 deaths in women. Al­most half of women are un­der 45 when they are di­ag­nosed. Cer­vi­cal cancer is gen­er­ally caused by HPV (hu­man pa­pil­lo­mavirus). The first stage is the de­vel­op­ment of pre-can­cer­ous cells, re­ferred to as cer­vi­cal in­traep­ithe­lial neo­pla­sia, or CIN. Pro­gres­sion from pre-can­cer­ous cells to cancer takes on av­er­age 10 to 20 years.

Cer­vi­cal cancer screen­ing was in­tro­duced to de­tect pre-can­cer­ous changes that could be treated to pre­vent them de­vel­op­ing into cer­vi­cal cancer. The screen­ing test is not de­signed for di­ag­nos­ing cer­vi­cal cancer, which presents with symp­toms such as ir­reg­u­lar vagi­nal bleed­ing, spot­ting or dis­charge, bleed­ing af­ter sex and/or pelvic pain. It is also pos­si­ble to de­velop cer­vi­cal cancer be­tween screen­ing tests, so women who have symp­toms such as vagi­nal bleed­ing or pelvic pain should al­ways see their GP.

The Ir­ish cer­vi­cal screen­ing pro­gramme (Cer­vi­calCheck) was in­tro­duced in 2008 and aims to de­tect pre-can­cer­ous changes in the cells. Women at­tend their GP or prac­tice nurse (usu­ally) for what is com­monly called their smear test. This in­volves col­lect­ing cells from the cervix or neck of the womb, which are then sent to a lab­o­ra­tory for anal­y­sis. If pre-can­cer­ous changes are found and thought to be very sus­pi­cious (high-grade ab­nor­mal­i­ties), the woman is re­ferred to a spe­cial­ist for col­poscopy.

If there are minor changes in the cells (low-grade ab­nor­mal­i­ties), the sam­ple is checked to see if the HPV virus is pre­sent. If HPV is de­tected, the woman is re­ferred for col­poscopy. Dur­ing col­poscopy, the spe­cial­ist takes a more de­tailed look at the cervix and may take a biopsy and/or ap­ply treat­ment to the ab­nor­mal area.

The biopsy is as­sessed in a lab­o­ra­tory where it is in­ter­preted as ei­ther nor­mal, pre-cancer (CIN) or cer­vi­cal cancer (though this is not al­ways ap­par­ent). Fur­ther treat­ment and mon­i­tor­ing of the ab­nor­mal­i­ties is de­ter­mined by the spe­cial­ist in the col­poscopy or gy­nae­col­ogy clinic.

It is im­por­tant to re­mem­ber that no screen­ing test is 100 per cent ac­cu­rate – some re­sults can be false pos­i­tives (ie, the screen­ing test says the re­sult is pos­i­tive, but there is no clin­i­cally sig­nif­i­cant dis­ease on fur­ther test­ing), and some are false neg­a­tives (ie, test re­sult is neg­a­tive, al­though dis­ease is ac­tu­ally there – this leads to de­layed di­ag­no­sis, which for cer­vi­cal cancer screen­ing means a de­lay in di­ag­nos­ing pre-can­cer­ous changes, which could then progress to cer­vi­cal cancer).

There is a pro­posed new cer­vi­cal cancer screen­ing strat­egy that is due to be in­tro­duced shortly in Cer­vi­calCheck. In the new sys­tem, all sam­ples will first be tested for HPV and fur­ther tests will be car­ried out on those who test HPV-pos­i­tive.

The main ad­van­tage of the new test is that it has fewer false neg­a­tives. This means that as­sum­ing 250,000 women at­tend for screen­ing each year in Cer­vi­calCheck, in women with a neg­a­tive screen­ing test, 12 will go on to de­velop in­va­sive cer­vi­cal cancer within 3.5 years and 22 will go on to de­velop in­va­sive cer­vi­cal cancer within 5.5 years, and this in­cludes true neg­a­tives and false neg­a­tives.

This new test is in use in the UK al­ready and this is a sum­mary of the in­for­ma­tion that is given to women:

one in 20 women will have an ab­nor­mal smear test re­sult

one in 2,000 have cer­vi­cal cancer

So only 1 per cent of women with an ab­nor­mal smear will have cancer

Pre­vent­ing cer­vi­cal cancer

All of us want to pre­vent cer­vi­cal cancer so women and their fam­i­lies do not have to un­dergo highly chal­leng­ing treat­ments and ex­pe­ri­ence per­sonal tragedy. Cer­vi­cal screen­ing will never pre­vent all cases of cer­vi­cal cancer.

We do know the HPV vac­cine pre­vents cer­vi­cal cancer. It is of­fered free of charge to girls in the first year of sec­ondary school, with ev­i­dence to sup­port ex­pand­ing the vac­ci­na­tion pro­gramme to in­clude boys. HPV vac­ci­na­tion pre­vents seven out of 10 cer­vi­cal can­cers and works best when given at the age of 12 to 13 years. It also pro­tects against a range of other can­cers that oc­cur in men and women.

All in­ter­na­tional ev­i­dence in­di­cates the vac­cine is ex­tremely safe and it rep­re­sents our best chance to en­sure as few women as pos­si­ble ex­pe­ri­ence cer­vi­cal cancer in the fu­ture.

In the new sys­tem, all sam­ples will first be tested for HPV and fur­ther tests will be car­ried out on those who test HPV-pos­i­tive Go­ing for­ward

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