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Studies Raise Questions About Partial-Breast Irradiation


 

ORLANDO — Whole-breast irradiation resulted in no overall survival benefit over partial-breast irradiation in women with early breast cancer in a meta-analysis of three randomized clinical trials.

There were no statistically significant differences between the two therapies with regard to death (odds ratio, 0.91; P = .550), distant metastasis (OR, 0.74; P = .120), or supraclavicular recurrences (OR, 1.41; P = .560), according to a late-breaking abstract at the annual meeting of the American Society of Clinical Oncology.

Women treated with partial-breast irradiation were twice as likely to have local recurrence (OR, 2.15; P = .001), however, and three times more likely to have axillary recurrence (OR, 3.43; P less than .0001).

“Partial-breast irradiation may be safe and feasible for women with early-stage breast cancer because it does not jeopardize patient survival or the risk of metastasis,” coauthor Dr. Davide Mauri of the General Hospital of Lamia (Greece) told reporters at a press briefing. “Locoregional issues need to be further addressed.”

The findings are reassuring in terms of equivalent overall survival and reduction in risk of metastasis, but are not enough to change practice, said Dr. Jennifer Obel, who moderated the briefing. “Before we say from a meta-analysis that this should be the next standard of care for treating women with early-stage breast cancer, there are many randomized studies sponsored by major cooperative groups … that are forthcoming in the next couple of years and we should await those before we make our decision,” said Dr. Obel of NorthShore University HealthSystem in Chicago's Northern suburbs.

Two trials that could provide additional insights are the TARGIT (Targeted Intraoperative Radiation Therapy) trial in Europe and the National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 trial in the United States, Dr. Obel said in an interview.

The U.S. phase III trial will compare the effectiveness of the two irradiation strategies in 4,300 women after lumpectomy for early-stage breast cancer. It will use three technologies: high-dose-rate multicatheter brachytherapy, high-dose-rate single-catheter balloon brachytherapy (Mammosite), and three-dimensional conformal external beam radiation therapy.

“It's one of the largest trials of its size that will be looking at whole-breast irradiation compared to various techniques of partial-breast irradiation,” she said. “These are the some of the most patient-friendly techniques.” She acknowledged that partial-breast irradiation improves patient compliance because it is typically given over 5 days, compared with 5 weeks or more for whole-breast radiation.

Dr. Mauri agreed that ongoing trials will further clarify whether partial-breast irradiation offers high efficacy with better cosmetic outcomes.

He suggested that technique may have played a role in biasing the locoregional recurrence results in the meta-analysis. Two of the three studies used a standardized field of radiation, irrespective of tumor size, which could have led to areas of disease being missed and increasing local recurrence. In addition, one of the studies included women with extremely large tumors as well as node-positive patients. “I think that this explanation makes this finding of increased local recurrence less concerning.”

The meta-analysis included a total of 1,140 women (575 randomized to whole-breast radiation therapy and 565 to partial-breast irradiation). Median survival follow-up ranged from 5 to 8 years. The investigators, led by Dr. Antonis Valachis of the University Hospital of Heraklion in Crete (Greece), disclosed no conflicts of interest.

The findings are reassuring in terms of survival and risk of metastasis, but not enough to change practice. DR. OBEL

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