Patients treated with stereotactic body radiation therapy seen to have an increased risk of non-cancer death.
A recent study found that stereotactic body radiation therapy (SBRT) can increase the risk of non-cancer death in patients with early stage non-small cell lung cancer (NSCLC).
The results, which were presented at the ESTRO 35 conference, showed high doses of this radiation therapy to the left atrium and the superior vena cava had the highest risk of death. Researchers analyzed data from 565 patients with early stage NSCLC between 2006 and 2013 treated with SBRT.
Researchers created a template image of the heart in order to determine how much radiation was delivered to which location in the heart. Information on radiation dosage amounts were added to figure out dose parameters for various parts of the heart, according to the study.
"Then we determined the association between these dose parameters and non-cancer death for each sub-structure and for each dose parameter," said Barbara Stam, PhD. "Finding if there is a relation between dose to sub-structures and non-cancer death is only relevant if this relation still exists when other factors that are known to be related to non-cancer death are also taken into account. Therefore, we performed a second statistical analysis, including factors such as age, lung function and performance status."
Approximately 58% of patients were still alive after a median follow-up of 28 months.
"We found that dose to all sub-structures of the heart were associated with non-cancer death for this group of patients. 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,” Dr Stam 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. This association remained after adjustments for the factors included in the second analysis.”
In the left atrium, for every 1Gy above the average dose (7.9 Gy), the risk of non-cancer related death increased by 1.5%, and other structures had an increase of 1 to 2%, the study found. Although researchers do not know the exact cause of non-cancer death, they hypothesized that the deaths were related to heart problems since radiotherapy has been found to adversely affect the heart.
"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,” Dr Stam concluded. “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. For early stage lung cancer patients, treated with SBRT, we still need to investigate if heart sparing is possible, what compromises need to be made and whether it can increase survival. Further research and a wider discussion on heart sparing at the cost of possibly a higher average lung doses is required.”