Cancer Research UK describes 9,200 new cases of oesophageal cancer per year in 2017. 70% are diagnosed at a late stage, being incurable and causing 7,925 deaths / year.
Treatments using chemotherapy and radiotherapy – and more recently hormone therapy - have improved patient survival in recent years, extending survival of stent patients after receiving a stent from an average of 3months in 2004 to currently 15-18months. Most oesophageal cancers present late and are not curable and most patients eventually require insertion of a stent (most commonly a nitinol stent) to keep the lumen of the oesophagus and allow the patient to continue to eat.
These stents were originally designed for use in blood vessels but have been adapted for use in the gastro-intestinal tract and oesophagus therefore subjecting the stents to a different working environment especially chemical, due to exposure of the low pH of gastric acid, but also mechanical due to the movement and compression of oesophageal function (peristalsis). As a consequence an increasing number of patients experience device failure, requiring repeat procedures.
The re-intervention rate at 6months reaches 60%, which is now resulting in increased stent failures, which necessitate further procedures, and puts the patient at additional risk.
By improving the properties of these nitinol stents, we can improve their working life and remove the need for removal and replacement. This will improve clinical outcome and patient experience and reduce the need for repeat procedures and the associated costs to the NHS.
Main questions to be answered
1. What are the failure mechanisms of currently used stents – does removal of the native oxide layer occur and is repassivation of the stent impeded in the oesophageal environment?
2. Can we increase time in service by changing the properties of the current stent composition by e.g. metal processing technologies affecting microstructure?
3. Can we alter the composition of the current stents to increase time in service without compromising the shape memory properties?
4. Are advanced coatings (including graphene) another option for increasing time in service?