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SABCS 2015: Breast-Conserving Therapy Provided Better Long-Term Outcome Than Mastectomy in Patients With Early-Stage Breast Cancer

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Key Points

  • Among women with early-stage breast cancer, those who received breast-conserving surgery plus radiation had improved overall survival after 10 years compared with patients who received a mastectomy, 76.8% vs 59.7%, respectively.
  • After adjusting for confounding factors, the researchers found that those who received breast-conserving therapy were estimated to be 21% more likely to be alive after 10 years that patients who received mastectomy.
  • Data from a subcohort also showed that patients who received breast-conserving therapy developed regional recurrences and distant metastases less often than those who received mastectomy. 

Among women with early-stage breast cancer, those who received breast-conserving surgery plus radiation had improved overall survival after 10 years compared with patients who received a mastectomy—76.8% vs 59.7%, respectively—according to a Dutch study by van Maaren et al. After adjusting for confounding factors, the researchers found that those who received breast-conserving therapy were estimated to be 21% more likely to be alive after 10 years that patients who received mastectomy.

In addition, there was no significant difference in disease-free survival between those receiving breast-conserving therapy and those receiving mastectomy. The study (Abstract S3-05) was presented at the 2015 San Antonio Breast Cancer Symposium held December 8–12.

Study Methodology

The researchers analyzed data from the Netherlands Cancer Registry on 37,207 women diagnosed with early-stage breast cancer from 2000 to 2004 and treated with either breast-conserving therapy or mastectomy. Multivariable Cox proportional hazard analysis was performed to estimate 10-year overall survival, stratified for T and N stage. Ten-year disease-free survival was determined in a subgroup of 7,552 patients with similar characteristics diagnosed in 2003, of which an active follow-up was conducted registering all recurrent events within 10 years.

Key Findings

Of the total 37,207 patients, 21,734 (58.4%) received breast-conserving therapy and 15,473 patients (41.6%) received a mastectomy. The subcohort consisted of 7,552 patients with similar distributions of treatments and characteristics.

In the total cohort, 10-year overall survival rates were 76.8% (99% confidence interval [CI] = 76.1–77.5%) after breast-conserving therapy and 59.7% (99% CI = 58.7–60.7%) after mastectomy. After correction for confounding, 10-year overall survival was better after breast-conserving therapy than after mastectomy (adjusted hazard ratio [HR] = 0.79, 99% CI = 0.75–0.83]).

In the 2003 cohort, 10-year disease-free survival rates were 83.6% (99% CI = 82.5-84.7%) after breast-conserving therapy and 81.5% (99% CI = 79.6–83.4%) after mastectomy. After correction for confounding, 10-year disease-free survival was comparable for both treatments (adjuste HR = 0.91, 99% CI = 0.77–1.07]).

All results were similar for all subgroups. In the 2003 cohort, 11.0% of the patients experienced distant metastases after breast-conserving therapy compared to 14.7% after mastectomy (P< .001). Regional recurrences were diagnosed in 2.1% of patients treated with breast-conserving therapy and in 4.0% of patients treated with mastectomy (P < .001). Percentages of local recurrences did not differ between the treatment groups.

“[Breast-conserving therapy] showed substantially improved [overall survival] compared to [mastectomy]. However, while [disease-free survival] was similar, patients treated with [breast-conserving therapy] less often developed [regional recurrences] and [distant metastases]. Although residual factors might explain part of the difference in recurrences, we hypothesize that radiation therapy might largely be responsible for better [overall survival] by eliminating residual tumor cells,” concluded the study authors.

“The take home message [from this study is that] breast-conserving therapy should be the treatment of choice, especially in the smaller tumors, when it is medically feasible and according to the patient’s wishes,” said Sabine Siesling, PhD, Senior Researcher at the Netherlands Comprehensive Organization, Utrecht, the Netherlands, Professor at the University of Twente, Enschede, the Netherlands, and a coauthor of the study, during a press briefing announcing the study results.

Dr. Siesling reported no conflicts of interest.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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