Radiation heart dose from MammoSite compared to IMRT for left-sided breast cancers

When compared to IMRT, MammoSite Brachytherapy does not always deliver lower doses of radiation to the heart during treatment of left sided breast cancers. That is the finding of a study presented today at the 48th Annual Meeting of the American Society for Therapeutic Radiology and Oncology in Philadelphia.

MammoSite is a form of brachytherapy that uses a balloon catheter to deliver radiation. The balloon is surgically placed at the site where the tumor was removed and radiation is delivered through the catheter. IMRT, or intensity modulated radiation therapy, is a highly sophisticated system of delivering external-beam radiation that allows advanced planning for accuracy and reduced side effects.

"In theory, MammoSite brachytherapy has generally been associated with lower doses to the heart for left-sided breast cancers, but in our study, we found that IMRT in some patients confers less radiation to the heart when treating areas close to the chest wall," said Alice Tsai, M.D., a resident in the Radiation Oncology Department at Fox Chase Cancer Center.

MammoSite brachytherapy was simulated in 101 women with left sided breast tumors treated with IMRT. The maximum heart dose delivered by MammoSite was calculated and compared to the maximum heart doses delivered by IMRT. The patients were divided then into two separate groups. Group I consisted of patients with the higher heart doses from MammoSite simulations. Group II consisted of those with the higher heart doses from IMRT.

The researchers analyzed data to determine the minimum distance from the chest wall to place the MammoSite implant in order to reduce the dose of radiation to the heart, but a uniform distance could not be determined, but other important conclusions were made.

"Our study shows that MammoSite brachytherapy does not always confer a lower heart dose than IMRT in women with left sided breast tumors," concluded Tsai. "Care must be taken when assessing women who are candidates for MammoSite brachytherapy with thorough evaluation of CT scans to minimize heart toxicity when left breast tumors are close to the chest wall."

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Fox Chase Cancer Center was founded in 1904 in Philadelphia as the nation's first cancer hospital. In 1974, Fox Chase became one of the first institutions designated as a National Cancer Institute Comprehensive Cancer Center. Fox Chase conducts basic, clinical, population and translational research; programs of prevention, detection and treatment of cancer; and community outreach. For more information about Fox Chase activities, visit the Center's web site at www.fccc.edu or call 1-888-FOX CHASE.


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