THURSDAY, March 5, 2020 (HealthDay News) -- Breast size should be considered when positioning a breast cancer patient during radiation therapy, researchers say.

Even at low doses, radiation targeted at breast tumors can also affect nearby organs such as the heart and lungs, so patients are positioned lying face down to protect the heart and lungs as much as possible, the researchers explained.

However, breast size may determine whether the face-down position is actually the best one for a patient, according to a New York University study.

It included 34 women with left-sided breast cancer. Because the heart is located on the left side of the body, radiation treatment for left-side breast cancer poses a higher risk to the heart than treatment for right-sided breast cancer, the researchers explained.

They used CT scans to simulate the dose of radiation the women's heart and lungs would receive in different positions, and also used the CT scans to measure breast volume.

Women with large breasts had less heart and lung radiation exposure when lying on their stomach, while those with smaller breasts had less exposure when lying on their backs and holding their breath, according to the study recently published in the journal Practical Radiation Oncology.

"Our findings confirm what we already suspected based on our clinical practice," said lead author Dr. Naamit Gerber, a radiation oncologist and assistant professor at NYU Langone Health and its Perlmutter Cancer Center.

"When women with large breasts lie face down, the breast tissue falls away from their chest, creating more distance between internal organs and the radiation. For smaller-breasted women, there is a bigger advantage to the breath-hold technique, which creates distance between the heart and the breast tissue," Gerber explained in an NYU news release.

The findings provide breast-size criteria for determining the best position for breast cancer patients during radiation therapy.

The researchers also said that their study found that radiation therapy for breast cancer results in very low levels of heart and lung exposure overall, regardless of a patient's position.

More information

Breastcancer.org has more on radiation treatment for breast cancer.