HealthDay News — For older women with invasive breast cancer, treatment with brachytherapy following a lumpectomy is associated with higher rates of subsequent mastectomy and more complications than standard treatment with whole breast irradiation, study results indicate.

Brachytherapy also failed to improve overall survival at 5 years (87.66% versus 87.04%, adjusted hazard ratio 0.94, P=0.26), Benjamin D. Smith, MD, of the University of Texas MD Anderson Cancer Center in Houston, and colleagues reported in the Journal of the American Medical Association.

“Potential public health implications of these findings are substantial, given the high incidence of breast cancer, along with the recent rapid increase in breast brachytherapy use,” the researchers wrote.

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They retrospectively analyzed data from 92,735 women (aged ≥67 years) with incident invasive breast cancer, diagnosed between 2003 and 2007 and followed up through 2008. Patients were treated with brachytherapy (6,952 women) or WBI (85,783 women) following lumpectomy.

Five-year incidence of subsequent mastectomy occurred in 3.95% of women treated with brachytherapy vs. 2.18% of women treated with WBI, the researchers found. This association remained significant after adjusting for other variables.

Additionally, brachytherapy was associated with significantly more frequent infectious and noninfectious postoperative complications (adjusted odds ratio=1.76 and 2.03, respectively), and correlated with significantly higher five-year incidence of breast pain, fat necrosis and rib fracture.

Numbers needed to harm by treating with brachytherapy instead of standard therapy were 56 for unnecessary mastectomy, nine for post-operative complications and 16 for all post-radiation complications.

“Although these results await validation in the prospective setting, they also prompt caution over widespread application of breast brachytherapy outside the study setting,” the researchers wrote.

They called for further studies with longer follow up periods and in younger patients not using fee-for-service Medicare insurance.

Limitations included inability to determine the effects of intraoperative radiotherapy, which was too uncommon during the study phase, the potential for misclassification by administrative claim, the inability to confirm whether subsequent mastectomies were due to cancer recurrence and lack of data on factors like cancer stage, histology, margins, and radiation dose.

Smith JL et al. JAMA. 2012; 307: 1827-1837.