Prempro's packaging information already recommends routine breast exams and mammograms for users, and Camardo said the follow-up results are "not anything that's particularly new that should change guidance."
Manson, the co-author, said it's possible the initial study results prompted hormone-using participants to see their doctors more often than nonusers after the study ended, which could have resulted in more cancers detected.
It's also possible hormones either triggered new tumors or fueled the growth of existing ones, the researchers said.
"Once a tumor gets started, you might think of it as a train is out of the station and it might be more difficult to stop it," Lauer said.
The follow-up involved 15,730 participants tracked through March 2005.
The authors said the decline in heart problems was not surprising, since harmful effects of hormones on blood vessels could be expected to fade after women stopped taking the pills. Also, heart risks during the study were highest soon after women started taking hormones.
Dr. Sherry Nordstrom, an obstetrician-gynecologist at the University of Illinois at Chicago, said the lung cancers were a surprising finding but called hormones "still very appropriate therapy" for women with bad symptoms.
Study participant Geraldine Boggs, a Washington, D.C. nurse with three daughters and four granddaughters, said women should pay attention to the new findings.
"I initially joined the study to make sure that my daughters and granddaughters had informed choices about taking them when they got to be my age," said Boggs, 64.
Boggs, in her early 50s when she enrolled, was assigned to take hormones. Still, she said she developed no health problems during the study or afterward, other than hot flashes for about a year after quitting the pills.
Dr. Nieca Goldberg, a New York University women's heart specialist, said the study underscores that in addition to cancer screening, women who stop taking hormones need to find other ways to keep their bones strong, including getting more calcium and exercise.
On the Net:
Hormone study: http://www.nhlbi.nih.gov/whi/estro-pro.htm
(Copyright 2008 by The Associated Press. All Rights Reserved.)