A new study published in the pre-print online edition of the Journal of Clinical Oncology, has found that women aged 50 to 76 who use hormone replacement therapy combining estrogen and progestin have a higher risk (50%) of lung cancer as compared to the non-users.

"Although HRT use has declined and is not recommended except for short-term treatment of menopausal symptoms, our results indicate millions of women may remain at risk of developing lung cancer", said Chris Slatore, Assistant Professor of Medicine in the Oregon Health & Science University School of Medicine.

For the study, the data collected from 2000 to 2002 in the Vitamins and Lifestyle Study in Washington State was reviewed by Slatore, who identified 36,588 pre and postmenopausal participants and followed them for six years using the Seattle-Puget Sound Surveillance, Epidemiology and End Results cancer registry.

It was observed that 344 of the participants had developed lung cancer with the use of estrogen and progestin for 10 or more years.

The mechanisms causing the association between HRT and lung cancer remain unknown, but the researchers suggest that genetic and environment interactions are responsible for the association.

HRT users, who took more than one alcoholic drink per day, had a 42% increased risk than the women who did not use HRT or alcohol.