Is there a link between radiation therapy and future heart problems in patients with small-cell lung cancer?

This study looked at the link between cardiac (heart) events in the years after radiation therapy in patients with small-cell lung cancer. The authors concluded that there is a long-term risk of cardiac events in patients treated with a combination of radiation therapy and chemotherapy.

There have been several reports linking radiation therapy to cardiac events (CE) such as heart attacks, heart failure or infection of the heart. For some types of cancer, the risk of heart failure 5 years after treatment involving radiation therapy is more than double that of treatment without radiation, depending on the dose of radiation. Several studies have looked at the association of radiation therapy (RT) and heart problems in non-small-cell lung cancer. There is very little information regarding small-cell lung cancer (SCLC) however and standard care for SCLC involves a combination of RT and chemotherapy.

The study included 7060 patients. 2892 (41%) patients had limited stage SCLC (LS-SCLC) while 4168 (59%) patients had extensive stage SCLC (ES-SCLC). Patients were divided into two groups. Group 1 patients were treated with chemotherapy and radiation therapy while group 2 patients were treated with chemotherapy only.

Before treatment, there was a higher occurrence of CE in patients who went into group 2 and these patients were therefore at a higher risk of further CE after treatment. 60 months after treatment, the occurrence of CE in group 1 patients was 62.3% compared to 36.2% in group 2. 

Overall survival (time from beginning trial until death) 1 year after treatment was 35% in group 1 and 21.4% in group 2.

The authors looked at patients specifically with LS-SCLC and included 2016 patients in this analysis. The 5-year occurrence of CE in group 1 patients was 50.3% compared to 42% in group 2 patients. There was a 20% increase in the risk of CE for patients who had been treated with RT.

In group 1, 69% of patients who had CE before treatment had one or more CE after treatment compared to 42.7% of patients who did not have CE before treatment.

The authors concluded that there is a higher risk of CE after treatment involving RT for patients with SCLC. The 5-year risk is 5% for patients with any SCLC. This risk increases to 10% for patients with LS-SCLC.

The study only included patients over the age of 65. There was no information regarding the dose of RT and on the different types of RT used and if they would have an effect on the risk of CE.