Lung cancer deadlier than breast cancer for women

Gains in early diagnosis coupled with new treatments are spurring hopes for increased survival rates in lung cancer patients.

By Susan J. Landers, amednews staff. Dec. 1, 2003.

Washington -- Lung cancer has had the dubious and little-known distinction of being the leading cancer killer of U.S. women since 1987. Many people mistakenly continue to rank breast cancer as claiming the most lives because it is the most common cancer among the nation's women.

However, this misconception is a case of deadly confusion.

Women at risk
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Lung cancer will be responsible for 25% of women's cancer deaths this year, while breast cancer will account for 15%, according to American Cancer Society estimates. Survival rates for breast cancer have also surged far beyond those for lung cancer.

While five-year survival rates for lung cancer are now 15% -- only slightly better than the 12% survival rates of 30 years ago -- survival rates for breast cancer have reached 88%.

"Women in the United States have the highest rate of lung cancer in the world, and they don't even know it," said Sheila Ross, Washington representative of the Alliance for Lung Cancer Advocacy, Support and Education and a lung cancer survivor. She was speaking at a Nov. 13 Capitol Hill briefing.

Researchers at the event also noted that while rates of lung cancer have been declining among men for many years, women's rates have increased until very recently, when they began to level off.

Of cancer deaths among American women, lung cancer accounts for 25% and breast cancer for 15%.

In addition, compared with men, women who smoke are more likely to develop lung cancer at a younger age and as a result of being exposed to lower levels of smoke.

Women are also more likely than men to develop small-cell lung cancer, which spreads quickly, and adenocarcinoma, which accounts for about 40% of lung cancer cases in women.

Adenocarcinoma is more difficult to treat because it involves cells lining the internal organs, in contrast with squamous cell lung cancers that begin on the surface of the lungs.

Estrogen is also thought to play a role in stimulating the growth of lung cells and may drive the carcinogenic process.

On the other hand, women diagnosed with the same type of lung cancer as men have a better prognosis, according to data gathered by the Society for Women's Health Research.

Smoking is still the major cause of lung cancer. Although smoking cessation efforts are reducing the numbers of smokers, about a third of adults in the nation still light up, said Robert A. Smith, PhD, director of cancer screening at the American Cancer Society.

Lung cancer is the leading cancer killer of American women.

However, even if everyone quit smoking, lung cancer would still be a major health concern.

The majority of people newly diagnosed with lung cancer are not smoking when they are diagnosed, said Jill M. Siegfried, PhD, co-director of the Lung Cancer Program at the University of Pittsburgh Cancer Institute.

She found that 13% of new lung cancers are diagnosed in people who have never smoked, 47% in former smokers who quit 15 to 20 years earlier, and 40% in current smokers.

The message that former smokers remain at continued risk for lung cancer many years after they've quit is not always effectively conveyed, noted researchers.

Diagnostic gains

The discouragingly low survival rate for lung cancer can be attributed to the failure to detect lung cancer early enough to effectively treat it, said Dr. Smith. Nearly half of lung cancers are diagnosed at stage 4, when they have already spread to other organs and to bones.

In contrast, detection at stage 1 can lead to a 60% to 70% survival rate.

The 5-year lung cancer survival rate is 15%.

Moving in that direction, researchers are focusing more attention on powerful spiral CT scanners and their ability to reveal small malignancies that are missed by x-ray, said Dr. Smith. Findings from a large New York trial found that low-dose CT scanners were able to reveal 27 malignancies compared with only seven by conventional x-rays.

The current quest is to determine which populations should be screened, said Dr. Smith. "Do we base it on age? Packs smoked?" he asked. There is a danger that harmless, noncancerous nodules picked up by CT scans could subject a patient to unnecessary and costly treatments.

The National Cancer Institute is currently enrolling 50,000 participants in a clinical trial intended to evaluate lung cancer screening. So far, recruitment is running well ahead of schedule, with 41,630 men and women at high risk for lung cancer already enrolled.

Dr. Siegfried has registered success in the treatment of lung cancer by combining the drugs Iressa (ZD1839 or gefitinib), which was approved for the treatment of lung cancer, and Faslodex (fulvestrant), which was approved for treating breast cancer. Both drugs are manufactured by AstraZeneca, Wilmington, Del.

More effective diagnostic tools coupled with combined targeted therapy offer "tremendous opportunity to put more effective work into lung cancer," she said.

ADDITIONAL INFORMATION:

Women at risk

A growing body of knowledge about women, smoking and lung cancer supports the notion that there is a dangerous gender gap.

Compared with men, women who smoke are more likely to develop lung cancer at a younger age and at lower levels of exposure.
One of the enzymes involved in breaking down the cancer-causing agents in tobacco smoke shows genetic variance, affecting men and women differently. One variant protects men, but not women, from lung cancer.
Nonsmoking women are more likely than nonsmoking men to develop lung cancer.
Estrogen may be partly responsible for women's greater susceptibility to lung cancer by increasing the effects of carcinogens such as tobacco smoke, cooking fumes and radon.
Women who have less exposure to estrogen throughout their lifetimes, such as those who undergo early menopause, could have a lower risk of lung cancer, while women who take estrogen replacement therapy could have an elevated risk.

Source: The Society for Women's Health Research