New figures published on the charity's website found that in 2007, 11 990 women in the UK died from breast cancer.
In 1971 - the first year these statistics were collected - 12 472 women died from the disease.
This figure rose steadily year-on-year, reaching a peak in 1989 when 15 625 women died.
But since then, breast cancer death rates have fallen by a third - from 41.6 women per 100 000 in 1989 to 26.7 women in 2007.
Research into diagnosing and treating breast cancer is the reason behind this fall.
This decline is linked to the widespread introduction of treatments given to women in addition to surgery, which include chemotherapy, radiotherapy and hormone treatments such as Tamoxifen and Anastrozole - which help to prevent the disease from coming back. The introduction of the NHS breast screening programme in 1988 has also played an important role.
Professor Peter Johnson, Cancer Research UK's chief clinician, said: "It's incredibly encouraging to see fewer women dying from breast cancer now than at any time in the last 40 years, despite breast cancer being diagnosed more often. Research has played a crucial role in this progress leading to improved treatments and better management for women with the disease. The introduction of the NHS breast screening programme has also contributed as women are more likely to survive the earlier cancer is diagnosed. We hope these new figures will encourage women over the age of 47 to attend screening and to know that even if a tumour is found, their chances of beating it are better than ever."
Breast cancer is now the most common cancer in the UK. 45 500 women are diagnosed with the disease every year - or 125 women each day. It is the second most common cause of death from cancer in women after lung cancer. In addition, about 300 men are diagnosed with breast cancer each year in the UK and around 90 men die from the disease. There was no significant difference in incidence or mortality among men with breast cancer during this period.
The risk of breast cancer increases as a woman ages - eight in 10 cases are diagnosed in women aged 50 and over. Obesity and alcohol consumption, along with reproductive factors such as more women having fewer children later in life - are thought to be fuelling rates of the disease which have increased by more than 50% over the last 25 years. HRT is also linked to breast cancer risk, although the number of women taking it has fallen, leading to a reduction in breast cancer incidence among women in their 50s.
Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "Although we are delighted that fewer women are dying from breast cancer, we will not become complacent. Every one of those 11,990 women who died in 2007 was someone's mother, sister, daughter, friend or colleague and Cancer Research UK - as the UK's largest funder of breast cancer research - is absolutely committed to finding new ways to help more women survive the disease."
Walnut consumption may provide the body with essential omega-3 fatty acids, antioxidants and phytosterols that reduce the risk of breast cancer, according to a study presented at the American Association for Cancer Research 100th Annual Meeting 2009.
Elaine Hardman, Ph.D., associate professor of medicine at Marshall University School of Medicine, said that while her study was done with laboratory animals rather than humans, people should heed the recommendation to eat more walnuts.
"Walnuts are better than cookies, French fries or potato chips when you need a snack," said Hardman. "We know that a healthy diet overall prevents all manner of chronic diseases."
Hardman and colleagues studied mice that were fed a diet that they estimated was the human equivalent of two ounces of walnuts per day. A separate group of mice were fed a control diet.
Standard testing showed that walnut consumption significantly decreased breast tumour incidence, the number of glands with a tumour and tumour size.
"These laboratory mice typically have 100% tumour incidence at five months; walnut consumption delayed those tumours by at least three weeks," said Hardman.
Molecular analysis showed that increased consumption of omega-3 fatty acids contributed to the decline in tumour incidence, but other parts of the walnut contributed as well.
"With dietary interventions you see multiple mechanisms when working with the whole food," said Hardman. "It is clear that walnuts contribute to a healthy diet that can reduce breast cancer."
