The environmental story is a complex onion", said Devra Lee Davis (World Resources Institute, Washington, DC, USA), speaking at a conference on breast cancer and the environment held at the Lemelson Center in Washington on June 5. For exposure to chemicals and radiation, timing can be more important than dose, she explained, because there are critical periods in development--eg, the first trimester of gestation and adolescence--when sensitivity to carcinogenesis is high.
On Cape Cod (MA, USA), where breast-cancer rates are high, the Silent Spring Institute is using computers to combine historical records of residence, land use, pesticide applications (to trees and to the numerous cranberry bogs), and the hydrology of drinking-water supplies in an attempt to decipher just how the environment affects breast-cancer risk. So far, said Steven Melly (Newton, MA, USA), one cluster of cases maps near contamination from munitions tests on a military reservation. Another detailed breast-cancer mapping project, founded by Lorraine Pace (State University of New York, Stony Brook, NY, USA), is under way for Long Island.
Concurrent with the increase in breast cancer in the industrialised world, there are also increases in testicular cancer, hypospadias, and cryptorchidism, and a decline in the proportion of male births, said Davis. These trends may be related to increases in environmental endocrine disrupters. But, said Mary Wolff (Mount Sinai Medical Center, Bronx, NY, USA), most epidemiological studies of the prime suspect, organochlorines, have lacked the power needed to reliably detect an increase in risk of less than two-fold. "We need to get better and smarter at using animal studies and cell-culture studies", said Davis, "and we need to do primary prevention before we have definitive epidemiological data, which in many cases would need prohibitively large studies".
H Leon Bradlow (Strang Cancer Research Laboratory, Rockefeller University, NY, USA) reported that a low ratio of the 2-hydroxyoestrone
metabolite of oestrogen to the 16-hydroxyoestrone metabolite has been associated with raised breast-cancer risk in three recent studies. Exercise and diets high
in fruits and vegetables raise this ratio, he said, while a variety of carcinogens lower it by inducing different classes of detoxifying enzymes.
The ratio of these metabolites in urine may be useful in screening for women at high risk for breast cancer, he added.
Also on the early detection front, US Assistant Surgeon-General Susan Blumenthal (George Washington University Medical Center, Washington, DC, USA) reported a "peace dividend". Artificial intelligence techniques developed to spot military hardware in spyplane photographs are now being applied to the analysis of mammograms in a multicentre clinical trial, she said.