Small differences in the way a patient lies during radiotherapy treatment for lung or oesophageal cancer can have a significant impact on how likely they are to survive, new research shows.
Differences of only a few millimetres can mean that the radiation treatment designed to target patients' tumours can move fractionally closer to the heart, where it can cause unintentional damage and reduce survival chances.
The research was presented at the ESTRO 37 conference in Barcelona by Corinne Johnson, a medical physics PhD student at the Manchester Cancer Research Centre at the University of Manchester.
She said her findings suggest that survival rates could be improved by amending treatment guidelines to ensure patients are positioned more accurately.
Although radiotherapy can play an important role in treating cancer, it has a number of side effects, with previous research showing that radiotherapy to the chest can have negative long-term effects on the heart, increasing the risk of heart disease.
Johnson and her colleagues studied a group of 780 patients with non-small cell lung cancer who were treated with radiotherapy.
For each treatment, patients were positioned on the treatment machine and an image was taken to confirm that they lay within 5mm of their original position.
They used the data from these images to gauge how accurately the radiotherapy dose was delivered over the course of treatment, and whether it was shifted slightly closer or slightly further away from the patient's heart.
When they compared the data with how likely patients were to survive, they found patients with slight shifts towards their hearts were around 30 per cent more likely to die than those with similar sized shifts away from their hearts.
When they repeated the research with a group of 177 oesophageal cancer patients, they found an even greater difference of around 50 per cent.
In both groups the pattern of survival remained even when researchers took other factors such as the patient's age into account.
