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Opinion: Cancer screening can't provide 100% certainty - but the programme saves many lives

A recent judgement said doctors must have absolute confidence that results are normal – unfortunately, that just isn’t possible, writes Dr Ciarán Ó Riain.

Dr Ciarán Ó Riain

AT SOME STAGE in the next fortnight, I will likely look down a microscope at a biopsy sample from a young woman.

The form accompanying the biopsy may state “advanced cervical cancer – biopsy to confirm”.

The doctor training to be a consultant pathologist sitting down with me has already seen cervical cancer under the microscope too many times before. The diagnosis will likely be one we can make with confidence.

She may comment on how the woman is the same age as her. We never meet the woman but we know that soon a doctor will have the task of communicating our life-changing report to a young woman and her loved ones.

The next biopsy we look at may be from a woman of similar age. She has the very earliest form of invasive cervical cancer, small buds of tumour measuring only one or two millimetres. The edges of the biopsy are normal. Treatment is over. A hysterectomy can be avoided. 

The same doctors meet the woman in a clinic a week later to tell her with some confidence that her early stage cancer has been fully treated and the outcome will likely be good. Her dreams of a family and a long life can remain.

Both women may have partaken in our screening program, attended for every smear test on schedule,  done everything asked of them. Screening may only have worked for one of them.

Fortunately, the precancerous changes and early cancers currently detected and cured by screening currently vastly outnumber the advanced cancers.

Over the course of the 10 years of the CervicalCheck program, over 50,000 high-grade precancerous changes have been detected and treated.  The incidence of invasive cervical cancer has fallen year on year over the last decade.  

Due to the heroic efforts of many, we have not only halted the precipitous fall in HPV vaccination levels but seen levels rise – an unprecedented achievement globally that will protect young women’s’ future.

Plans were afoot for the introduction of a screening test involving looking for the presence of the HPV virus as a first step – undoubtedly a better test although one still with false negatives.

Ruth Morrissey’s Case

On Wednesday, the full High Court Judgment of Mr Justice Cross in relation to the case of Ruth Morrissey was published.

It is a very human account of how a young woman’s life has been destroyed by cervical cancer.  

I would encourage all to read it, in particular, paragraph 50 of the judgment – which gives a compassionate view of the layers of the individual human tragedies we have seen unfold over the last year and how the judiciary must make difficult decisions.

Nobody ever wishes their surname to be part of a landmark medicolegal judgment.

The nuances of this landmark judgement will be examined and explained in the coming weeks by legal professionals.

As doctors, we can only explain the science of screening and outline our concerns as to the potential impact of the judgment on the future delivery of lifesaving cancer screening programs in Ireland. 

It is on this background that last Saturday’s headlines about the requirement for ‘absolute confidence’ in a test being normal raised alarm among so many among the medical profession and wider society.

Doctors across all specialities are now concerned as to the implications on how they use their clinical acumen – must a GP ensure with absolute confidence that every headache is nothing sinister?

Must every radiologist comment on the smallest speck on every chest X-Ray?

For me, it harked back to an era of the paternalistic, all-knowing doctor that many of us hoped we had left behind in favour of a shared decision-making process with patients and all the shades of grey that entails.

Absolute confidence

Undoubtedly the full judgement may be more nuanced but clarity will be required about whether the ” absolute confidence” standard is limited to a specific role of a cytology screener or whether it may set a precedent for other aspects of medical practice.

While the principle is in place in the UK since 1999, there is little doubt that we operate in a very different medicolegal environment in Ireland.

In any event, absolute confidence in anything being normal is something that most would feel uncomfortable with being a basic standard on our statutes.

Clarity will also be required with regard to the apparent dismissal of both the importance of avoiding false positives in a screening system and the need for cost-effectiveness (paragraph 72 of judgment).

Both are fundamental principles of any screening program, which invites large numbers of healthy individuals to submit to testing.

The ethical balance of screening is between preventing cancer in the individual and avoiding harm at a population level to the wider society. 

Tough choices

What harm are false positives compared to the consequences of a false negative?

It is undoubtedly true that screening programmes err on side of avoiding false negatives but that has to be balanced against the risk of over investigation and treatment.

As well as the anxiety associated with an abnormal finding, real physical consequences are possible; repeated biopsies of the cervix may cause problems in pregnancy, removal of breast tissue may be performed for a nodule that left undetected would never have affected a woman’s life, colonoscopy with its rare but real complications would increase.

Whatever one’s political views on taxation and spending, all realise that the health budget is finite.

Increasing expenditure on healthy people in screening programmes inevitably takes away from treating those with heart attacks, safely delivering babies and all the other core functions of our already overstretched health service.

Along with pathology colleagues, including cytopathologists from both our public and private screening laboratories, we have proposed a better way to move forward to answer questions of women around prior smear test results.

A model involving blind review of slides that mimics normal screening conditions and would answer the key question of whether the slide would have been consistently identified as abnormal.

It would be a fair process to all involved and would go some way to answering the question for women “could or should have things been differently for me?”.

Notably, similar models were rejected by the Justice as those of a vested interest in favour of the long-established adversarial approach of relying on expert witnesses.

Perhaps I am a vested interest. I look down a microscope for a living, I understand the limits of visual interpretation, I have and will make mistakes.

However, my main interest is that perhaps in twenty years time when I sit down with a young pathologist at a microscope, they might ask “what does cervical cancer look like? I’ve never seen it”.

Wouldn’t it be great if I could say that I hadn’t diagnosed cervical cancer in ages?

Wouldn’t it be great if a woman receiving the devastating diagnosis of advanced cervical cancer was an exceptionally rare event? 

We can and must work together to ensure that in the pursuit of perfection we do not lose our common good of all our screening programs.

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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Dr Ciarán Ó Riain

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