Professor John Tidy

Professor John TidyJohn Tidy is a Professor of Gynaecological Oncology at the Sheffield Teaching Hospitals NHS Foundation Trust, UK. He has worked to develop the clinical applications of electrical impedance spectroscopy and is clinical founder of Zilico Ltd.

Why is it important to improve diagnostic techniques for cervical cancer?

The first stage of screening, the cervical smear or pap  test, has improved significantly in recent years, but it remains a subjective test - a personal opinion.  A cytopatholgoist and their colleagues, in the laboratory, assess the cells present in a cervical smear for the presence of changes suggestive of pre cancer . Despite the improvements in the organisation of screening programmes, education and training all cervical screening programmes based on cervical cytology are subject to both false positives and more worryingly false negatives.

The middle stage of testing is the colposcopy and here results are very much down to what the individual colposcopist recognises as normal or abnormal.  To detect any abnormality a colposcopist will apply a dilute solution of acetic acid to the cervix and areas of the cervical tissue that turn white may represent precancerous changes. Because the colposcopist has to grade these changes in ‘whiteness’ a colposcopic opinion of any abnormality is subjective and prone to considerable variations in opinion. In addition it’s very difficult to get representative still images or video that can allow the diagnosis to be “quality assured“ by colleagues.

The final stage is biopsy and, as in screening, the results are interpreted in the laboratory. There is room for error in each of these stages and there can also be significant waiting periods for patients.

How will this technique benefit clinicians?

Electrical impedance spectroscopy (EIS) has the potential to improve the ability to detect high-grade CIN (cervical intra-epithelial neoplasia): the abnormal cells detected during the screening process. We want to treat women with high-grade CIN because there is a risk it will develop into cancer. But what we don’t want to do is to treat patients with low-grade CIN, as these cells are unlikely to develop into cancer.

Clinicians are starting to favour the “see and treat” method, where a patient receives treatment on their first visit. If a clinician assesses a patient as having high-grade CIN, they will treat it immediately. The advantage of EIS is that it might allow the clinician to distinguish between high- and low-grade CIN, and so reduce the number of patients who are over-treated and the number of biopsies carried out.

How will this technique benefit patients?

The benefit to patients is that they will get an immediate and objective result. It will reduce the need for biopsies, sparing patients a painful process often associated with bleeding afterwards. With the improved detection of CIN, we have the potential to reduce over-treatment, particularly for those women who currently go through “see and treat”.

A further concern about over-treatment is that women treated for CIN using the most common form of treatment, loop-cone biopsy, may be at risk of premature labour in the future.

The screening device, which is being developed to assist with primary-stage screening will have the greatest impact in countries with lower healthcare resources because it will more efficiently screen out women who definitely need treatment.