Preventing cervical cancer in older Vietnamese women

Cervical cancer is a leading cause of cancer mortality in Vietnam with over 80% of deaths among women aged over 45 years. In Western countries, regular cervical screening allows cancers to be detected and treated, but cervical screening in Vietnam is rare and less than 5% of the population have ever been screened. This means that cancers are detected later and are often fatal.

Human papillomavirus (HPV) causes cervical cancer and is common in younger people in Vietnam. Research into how best introduce a vaccine to prevent future cervical cancers is currently being undertaken. However, little is being done to help women who are too old to be vaccinated and are now at highest risk of developing cancer. We propose to strengthen existing research partnerships between LSHTM and both the Pasteur Institute and Cancer Registry in Ho Chi Minh City (HCMC) in order to pilot an innovative HPV screening method among older Vietnamese women.

Our research in the UK has indicated that the majority of invasive cancers could have been detected by sensitive HPV testing compared to very few by cytology (a smear test). This project will pilot HPV testing in two districts of HCMC in 300 women aged 45-64 years. The women testing positive will be invited for repeat testing after 1 year and those still positive will be invited to undergo a therapeutic biopsy with the aim of greatly reducing their future cancer risk. In addition, 100 former sex workers will be identified and also invited to take part. These women are estimated to be at much higher risk of developing cervical cancer than the general population and therefore are an important target group for HPV screening. This pilot project will allow us to assess the response rate and also the attitudes to screening in those that accept their screening invite compared to those who refuse.

The cancer registry in HCMC is well organised but poorly resourced. Analysis of the data is required to understand unexpected changes in cancer rates which are likely to be due to migration in and out of the city. At least 50 cervical cancer patients identified by the registry will be interviewed in this pilot study to between understand their characteristics including whether they have moved from a rural area to HCMC.

In Vietnam, as in most LMICs, about 80% of cervical cancer deaths are in women aged over 45, and their risk will not be reduced by vaccination for at least 30 years. Organised screening is not feasible and a single cytology screen has low sensitivity. In contrast, the sensitivity of a single HPV test to identify women at long-term risk of developing cervical cancer is very high. A single HPV test around menopause with radical treatment of HPV positive women is a practicable means of achieving a large reduction in lifetime risk. No other feasible intervention in LMICs could achieve such a large and rapid reduction in incidence and mortality for any cancer.

Our primary aim is to develop and evaluate the methodology for a large population-based HPV screening study in collaboration with scientists at the Pasteur Institute in Ho Chi Minh City (HCMC). We shall estimate response rates by inviting a random sample of women aged 45-64 for HPV screening. Recruitment will continue until 300 have been screened. The response rate as well as knowledge of and attitudes to cervical screening for attenders and refusers will be analysed. A sample of 100 former sex workers aged 45-64 (FSWs) will also be contacted by a snowball method through FSWs already recruited to on-going studies.

Collaboration with the cancer registry is essential as linkage to cancer registration will provide lifetime follow-up for cervical cancer incidence. We shall also interview a sample of at least 50 cervical cancer patients contacted through the registry for case-control comparison with the population and FSW participants. We aim to explain HCMC's unusual cervical cancer incidence patterns: The rate in women aged 60-64 was among the highest in the world in 1995-99, and has since halved both in this age-birth cohort. A possible explanation is selective out-migration of FSWs at very high risk. This would have important implications for targeting high-risk women in rural areas in national screening.

The main eventual impact of the study will be on older women in Vietnam most of whom do not have access to any cervical screening. HPV testing in women aged over 45 years would enable early diagnosis of existing cervical cancers and pre-cancers and therapeutic biopsy of persistently HPV positive women will greatly reduce their future risk of developing cervical cancer.

The enhanced partnership between the LSHTM and the Pasteur Institute in HCMC will be a two-way process where the local investigators can learn from the UK experience of cervical screening and the LSHTM investigators will learn the challenges of introducing such a programme in LMICs. The experience gained by the cancer registries in both Vietnam and Mongolia will allow them to improve their data presentation and analysis skills.