According to results recently presented at the 29th Annual San Antonio Breast Cancer Symposium (SABCS), boost radiation among women with stages I-II breast cancer improves local control at 10 years but does not affect survival.

Following breast-conserving therapy, patients are recommended to undergo radiation therapy, unless contraindicated. Often women with early breast cancer will also receive a local radiation boost to the tumor bed. However, at least 10 years of follow-up was necessary to determine a potential survival benefit of boost radiation. Furthermore, researchers wanted to continue to evaluate the effects of boost radiation on specific age groups of women, as well as its potential long-term side effects. 

Researchers associated with the European Organisation for Research and Treatment of Cancer (EORTC) recently presented results from 10 years of follow-up from a clinical study evaluating radiation dose among women with early breast cancer. This study included 5,318 patients who had undergone complete excision followed by whole breast irradiation of 50 Gy. Patients were then randomized to a 16 Gy radiation boost to the tumor bed, or no further radiation. The median follow-up was nearly 11 years.

• Survival at 10 years was equivalent in both groups of patients (82%).
• Local recurrences at 10 years occurred in 6.2% of patients treated with boost radiation, compared with 10.2% for those who did not receive boost radiation (p<0.0001).
• At 10 years, local control was improved by approximately 10% among women aged 40 years or younger, approximately 4% among women aged 41-50 years, and 3% in patients aged 50 years or older.
• Severe fibrosis at 10 years occurred in 4.4% of patients treated with boost radiation, compared with only 1.6% of patients who did not receive boost radiation therapy (p<0.0001).

The researchers concluded that local control was improved, particularly in younger patients, by the addition of boost radiation therapy to the breast. However, boost radiation did not improve overall survival at 10 years.

Reference: Bartelink H, Horiot J, Poortmans P, et al. Impact of Radiation Dose on Local Control, Fibrosis and Survival after Breast Conserving Treatment: 10 Years Results of the EORTC Trial 22881-10882. Proceedings from the 29th Annual San Antonio Breast Cancer Symposium. San Antonio, Texas. Oral presentation December 14, 2006. Abstract #10.

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