A mysterious 30-year-long increase in breast cancer rates among Alaska Native women may finally be leveling off - after tripling between 1969 and 1998.

At least that's the hope, said Janet Kelly, an epidemiologist with the Alaska Native Tribal Health Consortium, addressing a local cancer symposium Tuesday.

While the incidence of breast cancer rose sharply among Alaska Native women toward the end of the 20th century - from 40 cases per 100,000 (from 1969 to 1973) to 138 cases per 100,000 (1994 to 1998) - it fell slightly to 132 cases from 1999 to 2004.

"But I think you'd be hard-pressed to say there's anything (like a decline) going on yet," Kelly warned health professionals attending a Mayo Clinic-led cancer conference at the Alaska Native Medical Center.

Whereas breast cancer was once relatively rare among Alaska Native women, it now matches the rate for white women nationwide - and exceeds by half the rate for American Indians and Alaska Natives who live in the Lower 48.

How come?

"We really don't know," Kelly said.

For the general population, however, some of the chief risk factors for breast cancer include obesity, lack of exercise, excessive alcohol consumption and hormone therapies, Dr. Sandhya Bruthi, a pathologist at the Mayo Clinic in Rochester, Minn., told the gathering.

No single lifestyle change has been shown to prevent breast cancer, Bruthi said, but controlling weight through diet and exercise reduces the risk, especially among women age 50 and older.

Tobacco use does not appear to be a factor in breast cancer - in fact it has an "anti-estrogenic effect" that may suppress its occurrence, Bruthi said - but it clearly contributes to lung cancer.

WHERE CANCER LIVES

Among Alaska Native women, susceptibility to different types of cancer appears to vary by geographical region, according to a new report on cancer in Alaska Natives from 1969 through 2003 authored by Kelly and Dr. Anne Lanier at the tribal health consortium.

The study found that while breast cancer was the most prevalent type of cancer among Alaska Native women in Anchorage and the Interior, colorectal cancer topped the lists among Native women in Barrow and coastal areas of western Alaska - like the Y-K Delta, where the breast cancer rate was only half the rate in Anchorage.

Since cancer in sparsely populated rural areas of Alaska occurs in numbers so small, it's hard to draw statistically valid conclusions, said Lanier, the director of the consortium's research office. But it's clear that cancer has grown rapidly among Alaska Natives.

"This is a population that - when I started working here 40 plus years ago - we didn't even think cancer was a problem," Lanier said. "And what we have observed is a dramatic change ... particularly in lung cancer, but also in breast and prostate, which are also going up."

According to the latest statistics:

• Breast cancer among Alaska Native women is now diagnosed more than twice as often as lung cancer, but lung cancer is twice as deadly as breast cancer (lung cancer resulted in 83 deaths from 2000 to 2004, compared to 40 deaths from breast cancer).

• Lung cancer was the most prevalent form of cancer among Alaska Native men - occurring at a rate 31 percent higher than for whites nationwide - followed by colorectal cancer and prostate cancer.

• Colorectal cancer was the most prevalent form of cancer for Alaska Native men and women combined, accounting for about a fifth of all cancers.

BEATING CANCER

Nationwide the occurrence of breast cancer in the United States has declined recently, falling about 3.5 percent a year from 2001 to 2004 - the first substantial downturn in the disease since the government began monitoring all cancers in 1975.

The National Cancer Institute estimates that 2.4 million women who had a history of breast cancer were alive in 2004, and a majority of them had become cancer-free.

In Alaska, from 2000 to 2004, breast cancer occurred among white women at a rate of 132.4 cases per 100,000 people - nearly equal to the rate for white women nationwide. But Alaska posted the nation's lowest mortality rate from breast cancer for white women (22.3 deaths per 100,000 people) over the same period.

The breast cancer rate among African-American women in Alaska (117.7 cases per 100,000) is slightly less than the average for all African Americans in the United States. (118.3 cases per 100,000).

Find George Bryson online at adn.com/contact/gbryson or call 257-4318.