Fragmin, a common blood thinner, could also be used to treat patients with lung cancer and improve the chances of survival.
Doctors at Velindre Hospital, in Cardiff, UK, are leading the Fragmatic trial - one of the world's largest lung cancer clinical trials - which will investigate how the drug might help prevent potentially deadly blood clots in lung cancer patients.
The Cancer Research UK-funded trial will determine whether Dalteparin (or Fragmin) can treat this problem and whether the drug may also improve the survival of lung cancer patients.
People with lung cancer are at an increased risk of blood clots in their veins because of chemotherapy, surgery, inactivity or the lung cancer itself. Clots can be dangerous and even fatal if they dislodge and travel to the lungs. They can also cause pain in the chest and breathlessness.
But fragmin may also have an anti-cancer effect and lead to an improvement in quality of life and survival rates after the lung cancer diagnosis. It is thought that the blood thinning drug may affect how cancer cells spread through the blood stream, but this is not known for sure.
The trial has been designed to help answer these questions and to identify any possible side-effects of using the drug in this situation.
The trial, which was created by Dr Fergus Macbeth and Dr Simon Noble at Velindre Hospital, is hoping to recruit 2,400 patients and is due to involve between 50 and 100 centres around the UK.
Dr Macbeth, the lead researcher on the trial, said, "Blood clots are quite common in people who have lung cancer and may be dangerous. With this research, we hope to learn how to reduce the risk of this problem and improve the treatment for patients. We are working hard to find better and more effective ways to treat this difficult illness."
Wendy Sweeting, from Machen, near Caerphilly, who is taking part in the trial, said, "I'm delighted to have the opportunity to assist medical science.
"Being on the trial means that I'm receiving a drug for thinning the blood and preventing blood clots, which has helped patients with other forms of cancer and which I might not have received otherwise.
"I'm receiving great care and kindness from my cancer team and I feel I'm helping research vital to improving treatment for many other patients like me."
Kate Law, Cancer Research UK's clinical trials director, added, "Lung cancer remains the second most common cancer in the UK.
"It is vital we continue to research new treatments and also improve existing treatments for the disease.
"Clinical trials like Fragmatic are important in helping to do this and developing better treatments for patients."