INDIANAPOLIS -- An Indianapolis doctor says lung cancer is afflicting younger, non-smoking women at an alarming rate.

Dr. Larry Einhorn, of Indiana University's School of Medicine, said Dana Reeve did not fit the typical profile of a lung cancer patient.

Einhorn, a world-renowned oncologist who is best known for treating cyclist Lance Armstrong's cancer a few years ago, said he never treated non-smoking women with lung cancer 30 years ago, but it is becoming more prevalent today.

Einhorn said he has recently treated many women under 50 who are battling the disease, some of them in their 20s. Like Reeve, those women are not and never were smokers.

Einhorn said the cause for the disturbing trend isn't completely clear, but he believes second-hand smoke is a factor.

"The same amount of tobacco exposure is more likely to lead to the changes that cause lung cancer in a woman than the male counterpart who gets the same second-hand exposure. Now, why that is, no one knows," Einhorn said. "It's sometimes too easy to say that this could be due to second-hand smoke. Probably some of the cases are due to second-hand smoke, but I would guess that the majority of them are unknown as to why these young healthy women like Dana Reeve develop this terrible disease and then succumb to lung cancer."

Lung cancer kills about 15,000 non-smoking women each year.