New Zealand breast cancer experts say a British study doubting the effectiveness of breast screening is alone in its assertions, and could persuade women to forego vital mammograms.
The Oxford University study found that 25 years of breast cancer screening had failed to significantly reduce the number of deaths from the disease, The Daily Telegraph reported.
University researchers said while deaths from breast cancer were reducing, there was "no evidence" it was because of the introduction of screening.
The study, published in the Journal of the Royal Society of Medicine, found the largest drop in mortality was for women aged under 40-years-old. In Britain, women of that age group are not routinely screened for breast cancer.
It also pointed to improved medications available.
However, the study conflicted with findings from the UK's Department of Health, showing the rate of deaths amongst women who were screened had decreased by 20 per cent.
BreastScreen Aotearoa was launched in New Zealand in December, 1998.
The Ministry of Health said nationally, breast cancer mortality per 100,000 women dropped from 25.2 in 1999 to 19.9 in 2009.
The rate of contracting the disease has stayed roughly the same, with 96 per 100,000 women in 1999 and 93 per 100,000 women in 2009.
Breast surgeon Erica Whineray Kelly, also a consultant with the National Breast Screening Programme, said the Oxford University study contradicted all other research into breast screening, including Danish studies, which were conducted over the longest period of time.
"It's going to stir a lot of debate," she said.
"I personally believe that our screening programme results in a reduction of deaths."
The danger of the Oxford study was that women might not think it necessary to undergo mammograms, Dr Whineray Kelly said.
Breast Cancer Aotearoa Coalition chairwoman Libby Burgess said the Oxford research was "unhelpful" in encouraging women to undertake breast screening.
She said the study conflicted with other "strong published data" that showed breast screening helped to reduce breast cancer deaths.
"It's a no-brainer actually; if you detect cancers early then you're treating for a cure, if you leave it until it's late and the cancer's had time to advance then you can't cure cancer.
"I would certainly want to encourage women to keep turning up, and in particular Maori women who have higher incidents and worse mortality rates than other ethnic groups in New Zealand."
Clinical leader of BreastScreen Aotearoa Marli Gregory said as at 2009, deaths from breast cancer had dropped by about a third since peak numbers in the late 1980s.
"This will be due to a combination of surgery, and additional therapy such as Tamoxifen, radiotherapy, chemotherapy - prior to the screening programme - and after 1999 early detection through breast screening.
"There has also been increased awareness among women about signs of breast cancer, and this may have led women - particularly younger women - presenting with symptoms earlier than they would have historically," she said.
A mortality review of BreastScreen Aotearoa is being carried out to judge how effective breast screening has been since the beginning of the programme, with results due within the next two years.
By the numbers:
• About 2800 breast cancer cases are diagnosed every year,
• The five-year survival rate has risen to about 85 per cent,
• More than 650 women die from the disease annually,
• Women most affected by breast cancer are those aged between 40 and 70, and
• The eligible age range for free breast screening in NZ is 45-69.
(Source: Breast Cancer Foundation and the Ministry of Health)