Dr Ciarán Ó Riain: Cancer screening is not perfect, but we need it

Healthcare is not without flaws, but the system does its job. Ciarán Ó Riain calls for calm in the wake of the latest smear test review, which found that CervicalCheck works

Dr Ciarán Ó Riain: Cancer screening is not perfect, but we need it

Healthcare is not without flaws, but the system does its job. Ciarán Ó Riain calls for calm in the wake of the latest smear test review, which found that CervicalCheck works

As a diagnostic pathologist, the focus of my working week is our multidisciplinary team meeting, where many disciplines discuss the management of women who have gynaecological cancer.

Included in the list of patients I receive each week will be a number of women who have invasive cervical cancer. Some will have a new diagnosis of cervical cancer and be hoping to avoid hysterectomy. Others may be facing into chemotherapy and radiotherapy. Yet others will be anxiously awaiting scan results to check for recurrence of cancer.

The aim of the meeting is to provide clarity, around diagnosis and management, that can inform discussions between women and their treating doctors.

Anyone who has attended these meetings will quickly realise that despite the expertise in the room, healthcare is an imperfect and increasingly complex task. Pathologists and radiologists will be aware of the pitfalls of our visual interpretations.

Surgeons and oncologists must aim to balance maximising the chance of cure with minimising the side-effects of their treatment.

I will never meet the women whose names are on our list. Nor have most of us met the women, or their families, who have been thrust into the spotlight since the CervicalCheck scandal broke in April 2018. Their stories, nonetheless, move us hugely.

None of the professionals who attend our weekly meetings, and who hear the stories of young women whose lives have been devastated by cervical cancer, would ever countenance defending a cervical screening system if it was found to be inadequate.

It is against this background that this week’s Royal College of Obstetricians’ and Gynaecologists’ (RCOG) report is important. It helps to answer (for affected women, for doctors, and for the population at large) whether or not our system was as good as it could be. Concerns around the quality of the service led 57,000 women to undergo additional ‘out of cycle’ screening tests. Indeed, a huge difficulty for my gynaecology colleagues in the early stages of this debacle was the lack of information on the quality of the service.

The Scally report not only addressed important wider issues around audit disclosure and governance, but also looked at laboratory quality and stated “there is no reason, on quality grounds, why the existing contracts for laboratory services should not continue.”

The RCOG review re-examined prior cytology tests of more than 1,000 women who had been diagnosed and treated for invasive cervical cancer. This was done to provide answers for each individual woman on her screening history and an overall evaluation of scheme quality.

The protocol reflected that used in England, which is the only country to publish findings of such ‘look back’ reviews. These reviews did not aim to replicate normal practice, but were performed ‘unblinded’: i.e. in the knowledge that the microscopic slides were from women who had subsequently developed cervical cancer.

The RCOG review compares the findings in CervicalCheck with that of a 2009-12 audit of more than 8,000 women in England who had cervical cancer. In both the RCOG review and the English audit, this ‘look back’ identified abnormalities in 40%-50% of slides that had originally been deemed to have no abnormality (negative).

Despite cervical screening being established in England for 30 years, a recently published report, looking at the years 2013-2016 in England, again showed ongoing, similar findings, with ‘upgrade’ rates in negative screening tests of more than 40%.

These figures sound alarming. Does this mean that the screening test is only right about half the time? Fortunately, far from it.

Amid all the confusing statistics, women can be reassured that for those who receive a result where no abnormality was detected, this report is correct more than 99% of the time.

What the report highlights is that, sadly, for the group of women who develop invasive cervical cancer, many will have changes identified on retrospective analysis of their previous screening test.

The report also notes that “to regard cancer as a screening failure is overly simplistic, because many of these cancers are actually screen-detected”. Indeed, 35% of women with differing interpretations between the original CervicalCheck report and RCOG review were diagnosed through screening at the very earliest stage of cervical cancer (stage IA1), a stage where the invasive cancer is so small that it can only be seen under a microscope.

Often, finding a definitive right answer is impossible for cervical cytology.

We know this from published literature, from the conflicting interpretations of expert witnesses and blinded reviewers in the cases that have come before our courts, and now we know it from the fact that some women will have three different interpretations of the same slide (original report, CervicalCheck audit, and RCOG review).

Despite these flaws, cervical screening works. There is no evidence that the quality aspect of cytology screening for women in Ireland has failed.

Doubtless, this is likely of scant consolation to those for whom screening has not worked.

We can improve detection by bringing in HPV primary screening, a better test but nonetheless an imperfect one, which will not identify up to 15% of abnormalities.

But cytology will remain as a key part of deciding which screened women should undergo further testing.

There are currently more than 100 legal cases against the national cervical screening system. As a society, we need to honestly address how we balance individual rights to legal action against the population benefits of an imperfect, but effective, high-quality screening system that simply cannot function in the face of multiple, costly legal actions.

As Dr Gabriel Scally has noted, we failed to hit the ‘pause button’ when these issues came to the fore in April 2018.

The publication of the RCOG review should now be a time of reflection for the medical, legal, political, and media communities on how we can work together to keep screening afloat.

In the first decade of CervicalCheck, more than 50,000 women had high-grade, pre-cancerous changes identified and treated. They are the relatively lucky ones, whose names never made it onto the list for our weekly cancer meeting.

If we fail to deal honestly with the imperfections of screening, that weekly list of women with cervical cancer will only grow longer.

- Dr Ciarán Ó Riain is a surgical pathologist with a specialist interest in gynaecological cancer diagnosis and staging. He is a member of the board of the Faculty of Pathology of the Royal College of Physicians of Ireland.

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