Key Points:

Clare Matheson still occasionally meets people who, when they hear her name, recall the "deceitful, unethical" experiment at National Women's Hospital in Auckland.

One such person she identifies as Gary.

"I know your name," he had said, and Mrs Matheson mentioned the hospital and her role in what she calls "the tragedy".

"Gary looked at me and said quite simply, 'My mother was one of those women. Of course we did not know at the time'."

She had cervical cancer and died when he was visiting her in the hospital. He was 17. His father was in nearby Green Lane Hospital after a heart attack.

Mrs Matheson, now 72, was "Ruth" in the 1987 Metro article that exposed the experiment in cervical pre-cancer and led to the inquiry by Dame Silvia Cartwright - which in turn revolutionised New Zealand's health system.

"Ruth" too was one of the women. But after her own treatment for cervical cancer, she had obtained her hospital files - a rarity at the time - and gave them to journalists Sandra Coney and Phillida Bunkle.

Mrs Matheson will today speak to a conference at Auckland University to mark 20 years since the Cartwright Report on what Metro had titled "An Unfortunate Experiment".

The experiment, led by gynaecologist Dr Herbert Green, investigated the idea that lesions called cervical intraepithelial neoplasia (CIN) 3 were not related to cervical cancer. Normal treatment of cone biopsy or hysterectomy was withheld from a group of women who had CIN3.

A follow-up analysis of the women in the experiment, published this year, found that those who had minimal disturbance of their lesion, by a small punch or wedge biopsy, had a greater than 30-fold increased risk of developing cancer over 30 years, when compared with women who were adequately treated.

Mrs Matheson said that when she went to a private specialist and learned she had cancer despite 44 visits to National Women's from 1964 to 1979, she felt "used and somewhat soiled". After meeting Coney and Bunkle, and reading their copy of a 1984 scientific article that had revealed the experiment to the international medical community, she realised she had been "used and abused like a laboratory rat" - and that scores of other women would have no idea their lives were in danger.

"This experiment was deceitful, unethical, callous and inhuman, and lacking in any moral foundation."

Dame Silvia's seven-month inquiry found that some patients had received inadequate treatment, and in some cases the women had died as a result.

Dr Green and three other doctors were charged with disgraceful conduct, although the charges against Dr Green, then 74, were dropped. The Medical Council found he was unfit to defend the charges. He died in 2001, aged 84.

The biggest change recommended by the inquiry report was the introduction of a national cervical screening programme, which is now credited with having reduced the cervical cancer incidence and mortality rates.

The report led to the medical disciplinary system being overhauled, opened to the public and complemented with processes to rehabilitate weak performers (systems now extended to other registered health practitioners); the creation of the Health and Disability Commissioner system; and the introduction of state-appointed ethics committees to oversee research.

It also greatly reinforced the concept of doctors having to fully inform patients.

"Prior to the report," said Solicitor-General David Collins QC, the former chairman of the Health Practitioners Disciplinary Tribunal, "informed consent was only spoken of in quite esoteric legal circles. It became literally a household phrase as a result of that inquiry."

The Cartwright Report resulted in:
* A national cervical screening programme.
* An overhaul of the medical disciplinary system.
* The creation of the Health and Disability Commissioner system.
* State-appointed ethics committees to oversee research.
* Reinforcing of the concept of doctors having to fully inform patients.