For centuries, time had seemed to stand still in the territory of Papua New Guinea, north of
Australia. As anthropologist Margaret Mead described in the 1930s, most people on the island
lived and died in their remote native villages, practicing the primitive traditions of their elders,
and rarely venturing more than a few miles from their homes.
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But in opening itself up to the West, this tropical nation of 4.5 million people has exposed itself to many so-called Western diseases. Just about every month, island health officials publish new data documenting how once-rare Western health problems obesity, heart disease, diabetes, alcoholism, drug addiction, and AIDS are on the rise in the Westernized segments of the nation's native Melanesian population.
And now, female breast cancer may be one more so-called Western malady to make the list. According to David Watters, M.D., a surgeon at the University of Papua New Guinea in Port Moresby, he and his colleagues have "reasonable documentation" indicating that breast cancer in the country has increased somewhat and tends to strike educated, or Westernized, women.
Watters would not release the exact nature of the increase prior to publication of his group's findings, which are based on a multi-year audit of the country's only breast cancer surgery unit in Port Moresby. But he and his colleagues note that they still have a lot more hypotheses than hard data to guide them in explaining the rise, and a lot more research is needed to stem the trend and help women fight the disease.
Around the Globe
Papua New Guinea, which occupies the eastern half of the island of New Guinea, certainly is not the first country or indigenous group to show an increase in breast cancer as it has become Westernized. Similar findings have been reported in Japan, Taiwan, China, and among American Indians, Hawaiians, and Alaska natives.
But, if Watters' data are correct, some say this Pacific nation offers one of the most unique perspectives yet to study the effects of Western lifestyle on breast cancer risk. One reason is that, although women living in the cities and towns have been exposed to Western culture, about 80% of Papua New Guineans still live in the roughly 12,000 or so small, isolated villages scattered throughout the four vast, geographically diverse regions. So remote can these villages be, over 800 indigenous languages are spoken on the islands.
Like their ancestors, most rural people live as subsistence farmers, having little contact with outsiders. In the Southern Highlands, one of the provinces in the Highland region, about half of its 316,000 inhabitants raise their own food and still do not participate in a Westernized cash economy, according to PNG's 1990 census. Most do not know their age or date of birth.
Given their cultural isolation from the West, rural women also probably have fewer of the
recognized "Western" risk factors for breast cancer than any of the other countries
or ethnic groups previously studied. Most are extremely active, eat very little fat, consume lots of
fruits and vegetables, bear many children, are shorter of stature than Western women, and
menarche occurs relatively late. Because the average female life expectancy is short, most
women also never reach menopause, when the risk of breast cancer is highest in Western women.
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As a result, breast cancer has always been extremely rare on the island. According to a retrospective study of cancers registered with the Tumor Registry of Papua New Guinea from 1958 to 1988, the incidence of breast cancer in the country was 2.4 per 100,000, most of which involved premenopausal women. Conversely, in the predominantly Caucasian Australian state of New South Wales, where Sydney is located, the rate during this period was 64.9 per 100,000.
The study, published in the journal Cancer by Martin et al. in 1992, also noted that the breast cancer rate remained constant on the island over these 30 years. This was not the case on the more developed Melanesian islands of Fiji and New Caledonia, which had far higher incidence rates of 13.7 and 27.3 respectively.
But, as Watters' soon-to-be-published data indicate, the breast cancer rate on PNG is no longer constant, and the worry is that, as the push to Westernize reaches more of the country and more rural women migrate to cities, the rate will continue to increase.
Future Concern
Given the vast cultural divide that still exists between Western culture and traditional village life, some scientists have said that, in theory at least, it may be easier in Papua New Guinea than in other countries to measure the advance of Westernization on a woman's breast cancer risk.
This could be especially true for the high-fat Western diet, now often trumpeted as a risk factor for breast cancer but which has been extremely hard to pin down scientifically. Most data on high-fat diets and breast cancer stem from observational studies, which presuppose that the information provided by participants on questionnaires or in personal interviews is indeed accurate. As many point out, the risk for error can be great, especially when people must remember their dietary habits over several years or when preexisting genetic and environmental risk factors potentially can modify the possible tumor-inducing effects of dietary fat.
But in traditional island villages, where women have few Western risk factors for breast cancer, measuring the effects of a more Westernized diet might be less complex. The traditional diet varies somewhat from region to region, but in general it includes little fat.
"People in the Highlands really are fat deprived," said William Alto, M.D., who served as assistant secretary of health for the Southern Highlands province during the 1980s. "The average diet in the Highlands is about 90% sweet potatoes, supplemented by greens, ferns, leaves, and rarely a rat or a can of fish."
Fatty Foods
Alto and others note, however, that the traditional diet is changing as high-fat Western foods, such as chicken, canned fish, and whole milk, have entered the country's cash economy. "In the Highlands at least, fat was a highly valued delicacy because people would literally have no fat in their diets," said Ronald Pust, M.D., of the University of Arizona School of Public Health in Tucson, who worked in Enga during the 1970s and continues to visit the island periodically on sabbatical. "So, when you can eat fat, you tend to eat more of it. There are a fair number of people now who are getting quite obese."
According to several observers, Papua New Guinea has become a dumping ground for cheap cuts of Western meat. "In any town, there will be what is called a kai shop, where prepared foods are served," said Alto, now with Maine-Dartmouth Family Practice in Fairfield, Maine. "There, people get the cheapest cuts of lamb from Australia and New Zealand, such things as lamb ribs and lamb tongue. Very, very high in fat, and people are really happy with that."
In Port Moresby, located on the island's coastal area and the most Westernized spot in the country, the confluence of traditional and Western diets can best be seen in the grocery aisle. Many women now pop into modern grocery stores to fill their carts mostly with imported Western foods, then go to nearby roadside markets to load up on more traditional fare.
Though Colonel Sanders may not yet have arrived in Port Moresby, other fast-food chains have. People now eat Western foods year round at the Australian-based Big Rooster chain or numerous other small shops in the city that serve up chicken, fish, or ground beef. They also have begun to consume Australian milk that contains vegetable estrogens, which some believe play a role in triggering breast tumors, in excess of the traditional diet. Others, however, argue that these "phytoestrogens" have a protective effect.
Though Watters and his colleagues say they have more hypotheses than hard facts to explain the rise in breast cancer, they already have generated some interesting leads.
One is that 80% of all breast cancer in the country is premenopausal, which jibes with earlier published reports from national tumor registry data. While this would seem to be a given in a country in which women have such a short life expectancy, some say the pattern is nevertheless interesting because it coalesces with reports from Africa that breast cancer there tends to have an earlier onset than in the West.
Assuming, as many molecular biologists now do, that breast cancer is not one disease but perhaps a hundred different diseases with distinct etiologies, this patten of premenopausal breast cancer could have much broader significance. "Two thirds of breast cancer is premenopausal in both the Solomon Islands and PNG, and this is also true in many other developing countries," said Watters.
Odd Patterns
Watters and his colleagues also know, based on a study of banked island breast cancer samples, that most tumors display on their surface a pattern of hormone-binding protein receptors that has not been seen previously. Published last year in The Lancet, the group found that 54% of the PNG samples tested negative for both estrogen and progesterone receptors. A previous study showed that about 20% of breast tumors in whites and 35 % in American blacks fit this profile.
Conversely, just 4% of PNG breast tumors were positive for both estrogen and progesterone receptors. In whites, nearly 60% of breast tumors in whites and 44% in American blacks test positive for both receptors.
Peter Donnelly, M.D., a leading author on the paper and a scientist at North Queensland Clinical School in Australia, said his group also has looked at the hormone receptor status in breast tumors from other native Pacific Island populations. He said the group plans to publish its findings later in the year.
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