Women may be more likely to survive lung cancer than men, new research shows.

The researchers can’t explain those survival differences. Biology might play a role, with lung cancer behaving differently in men and women, they write.

Lung cancer is the leading cause of cancer deaths for U.S. men and women.

The new study doesn’t change that fact. The researchers included Juan Wisnivesky, MD, of New York’s Mount Sinai School of Medicine.

Their findings were presented in Montreal at Chest 2005, the American College of Chest Physicians’ annual international scientific meeting.

Tracking Survival

Wisnivesky’s study included nearly 19,000 lung cancer patients from across the U.S. They had been diagnosed with non-small cell lung cancer -- the most common type of lung cancer -- between 1991 and 1999.

The patients all had stage I or stage II lung cancer. Non-small cell lung cancer is classified in stages, starting with 0 and continuing with Roman numerals I, II, III, and IV. A higher stage means that the cancer is more advanced and may be larger in size and more widespread.

The researchers checked a national database linked to Medicare records to see what lung cancer treatment, if any, the patients had gotten.

Some patients had only received surgery. Others had received radiation or chemotherapy. A third group hadn’t been treated.

More Women Than Men Survived

Women outlived men in all three groups (surgery, radiation or chemotherapy, and no treatment).

Overall, 54 percent of women lived at least five years after their diagnosis. That’s compared to 40 percent of the men.

Among untreated patients, women’s survival odds were 25 percent higher than those of men, the researchers report.

Survival remained significantly better for women than men even after other factors were taken into account. Those factors included age, race, cancer stage at diagnosis, income, geographic area, access to care, and treatment type.

Why the Difference?

The reasons why survival seemed to favor women weren’t clear.

Since the pattern was seen in untreated patients, the biology of lung cancer might differ in men and women, the researchers write.

Here’s how Wisnivesky explains it in a news release.

“In patients with lung cancer receiving treatment, women have shown a better response to therapy, resulting in better survival rates,” he says.

“Yet, new data suggest that even in untreated patients, women with lung cancer still live longer than men, despite the presence of other medical conditions or gender differences in life expectancy,” Wisnivesky continues.

“This suggests that the progression of lung cancer has a biological basis, with the disease being more aggressive in men than women,” he says.

By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: Chest 2005, the 71st annual international scientific assembly of the American College of Chest Physicians, Montreal, Oct. 29-Nov. 3, 2005. American Cancer Society: “How Many People Get Lung Cancer?” American Cancer Society, “Overview: Lung Cancer -- After the Tests: Staging.” News release, American College of Chest Physicians.