Using stereotactic body radiation therapy (SBRT) to treat patients with non-small cell lung cancer (NSCLC) may slightly increase the risk of dying from a cause other than cancer, according to research presented at European Society for Radiotherapy and Oncology (ESTRO) 35 (April 29-May 3, 2016; Turin, Italy).
Led by Barbara Stam, PhD, Netherlands Cancer Institute (Amsterdam), researchers analyzed data from 565 patients diagnosed with early-stage NSCLC between 2006 and 2013 who were treated with SBRT, a form of radiation therapy that uses focused, more accurate beams to kill cancerous cells while preserving unaffected organs. The primary aim of the study was to determine the link between high doses of radiation to organs other than the lungs, specifically to the heart, and rates of death unrelated to cancer.
To determine how much radiation was delivered to which substructures of the heart, researchers created a template image of the heart and its substructures, onto which they mapped the anatomy of the patients in the study. Information about the radiation doses each patient received was then used to estimate the doses delivered to each substructure.
Dr Stam reported that, after a median follow-up of 28 months, 58% of patients were still alive. In addition, doses to all sub-structures of the heart were found to be associated with non-cancer-related death for this group of patients.
Maximum dose to 2 substructures, the left atrium and small area of the superior vena cava, had the strongest association with non-cancer death after SBRT. In the left atrium, for every 1 Gy above the average dose of 7.9 Gy, the risk of non-cancer death increased significantly by 1.5%. For all other structures, the risk increased by between 1-2% for every 1 Gy.
Researchers were not able to determine the causes of non-cancer deaths, as most patients involved in the study were elderly and died at home without receiving an autopsy. However, they did theorize that it could be related to heart problems, since research in breast cancer has shown that radiotherapy can 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,” concluded Dr Stam. “Further research and a wider discussion on heart sparing at the cost of possibly a higher average lung doses is required," she told the audience.