[Health technology assessment report: HPV DNA based primary screening for cervical cancer precursors].

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OBJECTIVE OF THE PROJECT: The introduction of the HPV test as a primary screening test will cause important changes in the screening system based on cytology. The purposes of this report are: to define the best screening policies with HPV-based screening on the basis of the resulting efficacy and of undesired effects; comparing them to cytology-based screening; to identify their best conditions of application; to evaluate economic cost, feasibility and impact on the organisation of services of such policy in the Italian situation.

CONTENTS

This report contains a section on efficacy and undesired effects based on a systematic review of literature conducted in strict coordination with the preparation of a supplement to the European Guidelines for quality assurance in cervical cancer screening. This chapter corresponds to a preliminary version of the chapter of the European Guidelines on primary screening with HPV. The sections on costs, impact on organisation, and social, ethical and legal impact reflect the Italian situation; they are based on a review of the available Italian data (including unpublished data, mainly from on-going pilot projects) and on a structured analysis of what will result if the proposed protocol is applied to the Italian situation.

RESULTS

Efficacy and undesired effects. There is clear scientific evidence that a screening based on validated tests for the DNA of oncogenic HPV as primary test and applying an appropriate protocol is more effective than screening based on cytology in preventing invasive cancers of the uterine cervix. In addition, it entails a limited--if any--increase of the undesired effects both in terms of unneeded referral to diagnostic work-up and in terms of over-diagnosis and consequent overtreatment of spontaneously regressive lesions. The crucial elements of such protocol are the followings: HPV-positive women are not to be directly referred to colposcopy, but the use of triage systems is essential. The currently recommendable method is based on performing cytology in HPV positive women. If the result of this test is abnormal, the woman is immediately referred to colposcopy; if cytology is normal, the woman is invited to repeat a new HPV test after one year. In case such a test is still positive, the woman is referred to colposcopy; in case of negative result, the woman will be re-invited for a new screening round at the regular interval. In organised population-based screening programmes the interval after a negative primary HPV test should be at least 5 years. There is evidence that the 5-year cumulative risk of high-grade CIN after a negative HPV test is lower than the 3-year risk after a normal cytology. On the other hand, the probability of unneeded colposcopies and treatments would plausibly be relevant with 3-year intervals after a negative HPV test. HPV-based screening should not start before 30-35 years. There is evidence that below 30 years HPV-based screening leads to an increased overdiagnosis of CIN2 that would regress spontaneously, with consequent overtreatment. Some increase in overdiagnosis is plausible also between 30 and 34 years. Below such ages, cytological screening is the recommended test. Only tests for the DNA of oncogenic HPV, validated according to the European guidelines as for sensitivity and specificity for high-grade lesions, should be applied. There is no evidence that double testing with cytology and HPV is more protective than stand-alone HPV as primary test, although it entails a small and not relevant increase in sensitivity vs stand-alone HPV. On the contrary, there is evidence that double testing causes a substantial increase in referral to colposcopy and a decrease in its PPV. For this reason, if HPV is used as primary screening test, it is recommended not to add cytology in parallel. Cost and economic evaluation. It is estimated that, if the protocol described is applied, in the current Italian situation the overall costs of HPV-based screening are lower than those of conventional cytological screening applied at the current 3-year intervals, although the cost of each screening round is higher. Impact on organization. For reasons of quality and cost, both the interpretation of cytology and HPV testing require a centralisation. This need is particularly strong, in terms of costs, for HPV test execution. It is therefore recommended to perform the HPV test in a limited number of reference laboratories of large size. This also makes monitoring and evaluating the spontaneous activity easier. HPV-based screening entails problems of organisation related to the need of triage, to complex protocols and to reconversion of the activities of cytological interpretation. Social, ethical and legal impact. The communication of the result of the HPV test to women, particularly if positive, is a further crucial aspect in order to reduce not only the emotional impact, but also the possible risks that women are inappropriately managed or lost to follow-up. Great efforts must be put in the education of healthcare professionals, both directly involved in organised programmes or not, particularly private gynaecologists and general practitioners.

RECOMMENDATIONS

In conclusion, the crucial requirement to introduce HPV-based screening programmes is the capacity to guarantee the application of appropriate screening protocols. If protocols do not respect the criteria described above they can cause relevant increase of undesired effects and costs compared to cytology-based screening. Therefore they should be avoided, except in studies able to provide clear evidence about human and economic costs. For this purpose, correct education and information both to healthcare professionals and to the population is needed. In the Italian situation, where organised screening and a relevant spontaneous activity coexist, their interaction is crucial. Actions directed to integrate them and to guarantee as more uniformity of interventions as possible are needed, in particular through the integration of registries and thorough monitoring and a progressive homogenization of protocols. In order to grant the safety of transition, it is needed that the HPV-based organised screening activities are strictly monitored and that the National Centre for Screening Monitoring (ONS) ensures coordination. Knowledge about HPV based screening is still rapidly evolving. It is possible that currently on-going researches suggest changes to the optimal protocols in the next few years, particularly as for the management of HPV positive women. In addition, studies on the validation of new assays were recently published and others are expected. It is suggested to exploit the organised screening activity to produce scientific evidence, in order to clarify the still uncertain aspects of optimal protocols. Different protocols in terms of screening intervals, age of application and management of HPV positive women should be studied in the frame of controlled implementation, through multicentre projects coordinated by ONS. Finally, it is suggested the creation of a National working group to promptly update the recommendations for screening and the list of assays to be considered as validated. On the bases of the results obtained in the first vaccinated cohorts reaching the screening age, for the future, it will be crucial to deliver specific recommendations to the population vaccinated against HPV during adolescence.