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Boost may reduce effects of positive lumpectomy margins

Boost may reduce effects of positive lumpectomy margins

LOS ANGELES—Adding a radiation therapy boost to the lumpectomy site after lumpectomy with whole-breast radiation therapy reduces the risk of local recurrence, particularly among breast cancer patients with high-risk features, including positive margins.

Speaking at the ASTRO annual meeting (abstract 4), lead author Heather Jones, MD, of the University of Pittsburgh, presented the updated 10-year results of the EORTC Boost–No Boost Trial, along with a look at risk factors for recurrence.

At the time of the study, Dr. Jones was at the Holzer Center for Cancer Care, Gallipolis, Ohio. Principal investigator is Harry Bartlelink, MD, of the Netherlands Cancer Institute.

"Our patients who opt for breast-conserving therapy vs mastectomy have a nontrivial risk for local recurrence," Dr. Jones said. "Preventing such a local recurrence is an important clinical parameter, as there is now evidence that local control is indeed linked to long-term survival in our early breast cancer patients."

Study patients had stage I or II breast cancer and underwent lumpectomy followed by whole-breast irradiation with 50 Gy. Thereafter, the 5,318 patients with microscopically completely excised tumors were randomly assigned to no additional treatment or to a 16-Gy boost, while the 251 patients with microscopically incompletely excised tumors were randomized to a 10-Gy or 26-Gy boost.

Ten-year results from the group with completely excised tumors (J Clin Oncol 25:3259-3265, 2007) showed that the 16-Gy boost significantly reduced the cumulative rate of local recurrence, compared with no boost (7% vs 12%, HR 0.59).

"Unlike our 5-year update, our 10-year update shows that this relative reduction by the boost is seen in all age categories. Still, the absolute benefit is greatly obtained by our young patients, particularly those 40 years old and less," Dr. Jones noted. At the same time, the boost significantly increased the rate of severe fibrosis (4.4% vs 1.6%).

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