Cancer patients who beat the disease can die from preventable blood clots owing to failures in the NHS, according to a new report.
Up to 4,000 cancer deaths every year could be caused by blood clots.
Some of these are preventable, with hospitals failing to warn patients of the risks posed by chemotherapy, the study said.
Data obtained by the All-Party Parliamentary Thrombosis Group (APPTG) found 2.6% of cancer patients who died in the previous three years in England and Wales also had venous thromboembolism (VTE) listed as a cause of death.
The increased risk of VTE in cancer patients is greatest in the first few months after diagnosis, but can last for several years.
While receiving chemotherapy, cancer patients also have a seven-fold risk of developing VTE compared to patients without cancer, research has found.
The APPTG study found that many hospitals were not taking the right action to cut the risk or warn patients.
Fewer than half of NHS hospital trusts were providing patients with both written and verbal information about the risk of developing a blood clot during cancer treatment.
Furthermore, only 41% of trusts had dedicated arrangements for assessing the risk of suspected blood clots and dealing with them in chemotherapy patients.
Andrew Gwynne, chair of the APPTG, said: "It is a tragedy that in today's NHS a patient can beat their cancer, only to then die of a clot.
"We hope that by raising awareness of this overlooked issue, we can drive up patient safety and provide better outcomes for patients."
The APPTG received data from 87 hospital trusts in England and five trusts in Wales, alongside figures from the Office for National Statistics (ONS).
The chance of developing VTE varied by region, with 2% in the south of England and 3.6% in Wales.
On average, 1.7% of cancer patients in England and Wales had suffered with VTE over the past three years, the data also found.
Death rates involving VTE for patients with brain, lung and bladder cancers were particularly high in 2014 - at 2.6%, 2.5% and 2.3% respectively.
Eve Knight, chief executive of the charity AntiCoagulation Europe, said: "It is vital that we raise awareness of the importance of staying on medication to treat blood clots for at least six months in order to prevent unnecessary deaths."