Regular mammographic screening for breast cancer saves the lives of two women for everyone who is given unnecessary treatment, scientists said Wednesday, in a study which adds to a global row over screening programs. The British researchers said their work, which contradicts some recent studies on screening programs but confirms others, showed the benefits outweigh the harm screening can cause by picking up tumors that would not have presented a problem. “Unfortunately, we haven't yet got a flawless screening test, and some cases that are picked up wouldn't have needed treatment,” said Stephen Duffy of Queen Mary, University of London, who led the study. “But for every case like this, screening saves two women who would have otherwise died from breast cancer,” he said. Duffy's findings contradict the results of a Nordic study published last week which found no evidence that routinely screening women for breast cancer had any effect on death rates. The findings will also further fan a row which erupted in the United States in last November after public health officials on the US Preventive Services Task Force questioned whether annual screening mammograms for women under 40 actually saved lives and suggested raising the screening age to 50. Cancer doctors and advocacy groups decried the move, saying the changes would mean more women die of breast cancer. Breast cancer is the most common cancer in women worldwide, accounting for around 16 percent of all female cancers. It kills around 519,000 people globally each year. Although experts are at odds over whether routine screening is worth the trouble and expense, most wealthy nations have settled on a plan for regular screening after age 40 or 50 to try to find tumors when they are small and more easily cured. Critics of screening programs say they can be more harmful than helpful if the extra hospital time and costs they require, coupled with the stress and worry of false alarms, are not outweighed by the benefit of preventing more deaths. Duffy and colleagues conducted two studies into the risk-benefit balance of screening programs. One study predicted the number of women who would have died from breast cancer in Britain if the breast cancer screening program had not been launched in 1988, and another looked at the number of breast cancer deaths among 80,000 women in Sweden, comparing those offered screening with those who were not. The results, published in the Journal of Medical Screening, showed a “substantial and significant reduction in breast cancer deaths” from mammographic breast cancer screening with “between 2 and 2.5 lives saved” for every over diagnosed case. Study links chemical exposure to breast cancer Exposure to certain chemicals and pollutants before a woman reaches her mid-30s could treble her risk of developing breast cancer after the menopause, Canadian scientists said Thursday. In a study in Occupational and Environmental Medicine, a British Medical Journal title, the researchers found that women exposed to synthetic fibers and petrol products during the course of their work appeared to be most at risk. “Occupational exposure to acrylic and nylon fibers, and to polycyclic aromatic hydrocarbons may increase the risk of developing postmenopausal breast cancer,” they wrote. But some experts commenting on the study expressed caution, saying such links can crop up by chance. The Canadian scientists conceded their findings could be due to chance, but also said they were consistent with the theory that breast tissue is more sensitive to harmful chemicals if the exposure occurs when breast cells are still active - in other words, before a woman reaches her 40s. The researchers, led by France Labreche, of the Occupational Health Research Institute in Montreal, Canada, based their findings on more than 1,100 women, 556 of whom were diagnosed with breast cancer in 1996 and 1997 when they were aged between 50 and 75 and had gone through the menopause. A team of chemists and industrial hygienists investigated the women's levels of exposure to around 300 different substances during their employment history. After taking account of the usual factors associated with an increased risk of breast cancer, the analysis indicated a link between occupational exposure to several of these substances, Labreche's team wrote. Compared with the comparison group, the risk peaked for exposures before the age of 36, and increased with each additional decade of exposure before this age, they found. This meant women who were exposed to acrylic fibers appeared to run a seven-fold risk of breast cancer, while those exposed to nylon fibers almost doubled their risk. The scientists said more detailed studies focusing on certain chemicals were now needed to try to establish what role chemical exposure plays in the development of breast cancer.
