Mastectomy Risk High With Brachytherapy for Breast Cancer

Neil Osterweil

December 07, 2011

December 7, 2011 (San Antonio, Texas) — Women who have partial-breast brachytherapy after surgery for invasive breast cancer have more than double the risk for later mastectomy and nearly double the risk for serious complications compared with those who undergo surgery and whole-breast irradiation (WBI), according to findings presented here at the 34th Annual San Antonio Breast Cancer Symposium (SABCS).

A retrospective review of Medicare claims on 130,535 women older than age 66 years showed that surgery plus accelerated partial-breast brachytherapy was associated with a hazard ratio for mastectomy of 2.2 (95% confidence interval [CI], 1.89 - 2.61; P < .001), reported Benjamin D. Smith, MD, assistant professor in the Department of Radiation Oncology at MD Anderson Cancer Center in Houston, Texas, and colleagues.

Brachytherapy was also associated with a near-doubling in risk for postoperative infectious complications (adjusted odds ratio [OR], 1.75; 95% CI, 1.63 - 1.87), and noninfectious complications (adjusted OR, 1.99; 95% CI, 1.86 - 2.13).

"Our findings highlight the complex choices that patients have to make with their doctors when choosing between 2 different radiation treatment strategies," said Dr. Smith in a briefing.

Dr. Smith says that he was "shocked" by the findings because the investigators did not expect to detect a large difference between the treatment types by using a claims-based analysis rather than a randomized, controlled trial.

"This work really underscores the importance of using data from randomized trials to make treatment decisions," commented Jennifer A. Ligibel, MD, from the division of Breast Oncology at the Dana Farber Cancer Institute in Boston, Massachusetts. She moderated the briefing in which the data were presented but did not participate in the study.

"Although the difference in mastectomy rates was only an absolute value of 2% with a short follow-up, this, coupled with a higher incidence of complications, should really be something that people consider in their practice in the coming weeks and months as they think about using this radiation technology rather than standard radiotherapy," said Dr. Ligibel.

The investigators reviewed Medicare billing claims data on women older than 66 diagnosed with incident invasive breast cancers and treated with breast-conserving surgery and either brachytherapy (7291 women) or WBI (123,244) from 2000 through 2007.

They looked at the cumulative incidence of subsequent mastectomy as a surrogate endpoint for local failure and at postoperative and postradiation complications.

They found that the 5-year cumulative incidence of mastectomy was 4% for women who had undergone brachytherapy, compared with 2% for those who had undergone WBI.

Within the first year after diagnosis, 16% of patients who went on to brachytherapy developed infectious complications related to surgery, compared with 10% of patients who went on to WBI. Noninfectious complications, such as surgical wound breakdown, bleeding, or seroma, were seen in 16% of mastectomy patients and 8% of the WBI patients.

Acute postradiation complications were also significantly higher among patients receiving brachytherapy, including risk for hospitalization (9.6% vs. 5.7%; adjusted OR, 1.71; 95% CI, 1.58 - 1.86; P < .001) and infection (8.1% vs. 4.5%; adjusted OR, 1.85; 95% CI, 1.69 - 2.02; P < .001).

In addition, brachytherapy was associated with a higher 5-year cumulative incidence of breast pain (14.9% vs. 11.7%; P < .001), fat necrosis (9.1% vs. 3.7%; P < .001), and rib fracture (4.2% vs. 3.6 %; P < .001). In contrast, the incidence of pneumonitis was lower in those undergoing brachytherapy (0.1% vs. 0.8%; P < .001) compared with WBI.

In an interview with Medscape Medical News, Alphonse Taghian, MD, a radiation oncologist at Massachusetts General Hospital in Boston, pointed out that although the differences in outcomes appear at first blush to be dramatic, the absolute differences between the treatment groups were low. He also noted that there is a learning curve with brachytherapy and that results from the technique as it is performed in 2011 would probably be similar to those seen with WBI.

The study was limited by the retrospective nonrandomized design, limited data on tumor characteristics, limited follow-up (median, 3.5 years), and lack of applicability to other partial-breast irradiation techniques, Dr. Smith said.

The authors disclosed that their group has received research funding from Varian Medical Systems, although that funding was not used to support the study, which was internally funded.

34th Annual San Antonio Breast Cancer Symposium (SABCS): Abstract S2-1, Presented December 7, 2011.

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