London : Treating patients who have early stage lung cancer with radiotherapy can increase their risk of death from causes other than cancer, says a study.

In particular, they found that high doses to the left atrium of the heart and the superior vena cava 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 the Netherlands Cancer Institute, Amsterdam.

“Validation and further investigations into the exact mechanisms and which heart structures are critical is warranted, but clinically, this could mean that patients might benefit from heart-sparing radiotherapy,” Stam noted.

The findings were presented at the European Society for Radiotherapy & Oncology’s ESTRO 35 conference on Monday.

The 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 a type of radiotherapy called 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, the 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.

Radiotherapy for lung cancer patients is linked to increased risk of non-cancer deaths, the findings showed.

As a result of the new findings, researchers said they would be investigating ways to deliver radiotherapy while sparing the crucial heart structures as much as possible.