Drugs used to treat breast cancer may also be useful in tackling lung cancer, according to research in Switzerland.
The study, published The Cancer Journal, showed that anti-oestrogens reduced the number of deaths from lung cancer.
The authors said the research, if backed up, could have substantial implications for clinical practice.
Cancer Research UK warned that large scale clinical trials were needed before any conclusions could be made.
Hormones have long been associated with some forms of cancer.
Tamoxifen, which cancels out the sex hormone oestrogen, was first used to fight breast cancer more than 40 years ago.
Some studies have shown that increasing levels of oestrogen, through hormone replacement therapy, increase the risk of lung cancer.