Radiotherapy may affect lung cancer patients adversely: study

Treating patients who have early stage lung cancer with radiotherapy may increase their risk of death from causes other than cancer, a new study has claimed.
Researchers found that high doses to the left atrium of the heart and the superior vena cava - the large vein carrying deoxygenated blood from the head, arms and upper body to the heart - had the strongest association and increased risk of non-cancer death.
"Our results show that even within a few years a radiation dose to the heart is associated with an increased risk of non-cancer death for early stage lung cancer patients, and they indicate which regions of the heart possibly play a role," said Barbara Stam from Netherlands Cancer Institute.

Researchers analysed data from 565 patients diagnosed with early stage non-small cell lung cancer (NSCLC) between 2006-2013 in five institutions in Europe and North America, who were treated with stereotactic body radiation therapy (SBRT).
SBRT is a specialised type of external beam radiation therapy that can focus radiation beams with extreme accuracy on a tumour, thereby minimising the effect on nearby organs.
With multiple organs nearby, minimising the dose to one organ is likely to result in a higher dose in another organ.

In order to work out how much radiation was delivered to which sub-structures of the heart, researchers created a 'template' image of the heart and its sub-structures on to which they could map the anatomy of each of the 565 patients - a process called deformable image registration.

Information on the radiation doses for the patients was added, and this enabled the researchers to work out the dose parameters (such as minimum, average and maximum doses) for the various parts of the heart such as the right and left atria, right and left ventricles, superior vena cava, descending aorta and left pulmonary artery.
"Then we determined the association between these dose parameters and non-cancer death for each sub-structure and for each dose parameter," said Stam.
After an average follow-up of 28 months, 58 per cent of the patients were still alive, researchers said.
"We found that dose to all sub-structures of the heart were associated with non-cancer death for this group of patients," said Stam.

Two sub-structures had the strongest association with non-cancer death - the maximum dose on the left atrium and the dose to a small area of the superior vena cava, researchers said.
Patients with low doses on the left atrium combined with low doses on the superior vena cava have a higher chance of survival than patients with high doses on the left atrium combined with high doses on the superior vena cava, they said.
The associations between higher radiation doses to the left atrium and the superior vena cava and deaths from causes other than cancer were small but significant, researchers said.