Prone position more protective during breast radiation

Prone-rather than supine-positioning during breast radiation therapy for breast cancer reduces the amount of radiation that reaches the heart and lungs without sacrificing efficacy, according to a research letter published in JAMA. The finding, according to the letter, is important considering that the risks to the heart and lungs can remain for up to 20 years after treatment.

Researchers from the New York University School of Medicine in Manhattan performed a prospective, single-institution cohort study of women with stages 0 to IIA breast cancer between 2005 and 2008. Each woman received 2 computed tomography (CT) simulation scans, first in the supine position and then in the prone position. Simulation scans are used to help visualize organs and formulate positioning strategy before radiation begins. The investigators then compared how much of the heart and lungs were within the radiation field in each scan.

In all of the approximately 240 women eligible to participate, the researchers found that, compared with supine positioning, prone positioning always correlated with less exposure of the lungs, regardless of whether the cancer was in the right or left breast. In women with left breast cancer, prone positioning offered about a 91.1% reduction in in-field lung volumes. Similarly, in women with right breast cancer, prone positioning conferred an approximately 86.2% reduction in lung exposure.

Findings concerning the heart were almost as powerful. The investigators reported that in women with cancer of the left breast, prone positioning was more protective of the heart 85% of the time. Supine positioning offered greater protection of the heart to about 15% of the women, usually those with very small breasts. 

The researchers concluded that physicians should first perform a simulation on women in the prone position. If some of the heart is in the radiation field, then a second simulation should be done in the supine position to determine which is more protective.

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