Women who underwent lumpectomy for stage I or II breast cancer were 28% less likely to die from any cause and up to 16% less likely to die from breast cancer, compared with women who underwent mastectomy, Dr. E. Shelley Hwang and her colleagues reported Jan. 28 in the online issue of Cancer.
The 3-year disease-specific survival benefit for breast-conserving therapy (BCT) was most pronounced for chronic respiratory disease, for which lumpectomy was associated with a 54% decreased risk of death; heart disease, with a 49% decreased risk; and cerebrovascular disease, with a decreased risk of 36%.
The survival benefit varied with age, tumor size, and hormone receptor status but was significant in every subgroup, Dr. Hwang and her colleagues wrote (Cancer Jan. 28, 2013 [doi:10.1002/cncr.27795]).
"Our findings have important implications for understanding the overall benefit of BCT at the population level," wrote Dr. Hwang of the Duke University Comprehensive Cancer Center, Durham, N.C., and her coauthors. "These results provide confidence in the efficacy of BCT even among younger patients with HR-negative disease thought to be at relatively higher risk for local failure."
The team reviewed the records of 112,154 women who were treated for a new, unilateral T1/T2 stage I or II breast cancer diagnosed from 1990 to 2004. Most of these women (61,771) underwent a lumpectomy and radiation; the remainder underwent mastectomy without radiation. They were followed for a median of 10 years.
About a quarter of each group was younger than 50 years when diagnosed; another quarter was aged 70-80 years. A small portion (6%) was younger than 40 years.
Surgical approach evolved over the study period. Breast-conserving therapy increased from 37% in 1990-92 to 62% by 2002-04, while the rate of mastectomies declined.
The median tumor size was 1.5 cm; patients with larger tumors were more likely to have mastectomies. "Interestingly, the use of BCT varied by age even among tumors [smaller than and equal to] 2 cm where the youngest and oldest age groups had the lowest BCT rate. In [tumors larger than] 2 cm, BCT rate declined by age," Dr. Hwang and her associates said.
Over the follow-up period, there were 31,416 deaths; 39% of these were caused by breast cancer; 5-year overall survival was 89%.
To further explore the treatment-mortality interaction, the investigators divided the cohort into four groups according to age and tumor characteristics:
• 50 years or older, hormone receptor negative.
• 50 years or older, hormone receptor negative.
• Younger than 50 years, hormone receptor positive.
• Younger than 50 years, hormone receptor positive.
Women 50 years and older with HR-positive tumors who had BCT experienced the greatest survival benefit, compared with mastectomy patients (hazard ratio, 0.81). Women younger than 50 years with HR- positive tumors experienced the smallest benefit (HR, 0.93), but one which was still statistically significant.
The investigators also looked at 3-year overall and disease-specific survival. "Notably, BCT was associated with significantly lower 3-year mortality rates from all causes," including heart disease (HR, 0.51), chronic respiratory disease (HR, 0.46), and cerebrovascular disease (HR, 0.64).
The findings align with those of randomized trials showing the benefits of BCT, the authors noted.
"Despite this, recent studies have shown an increased rate of mastectomy for patient subgroups including younger women with early-stage tumors, many of which would have presumably been amenable to BCT," they wrote. This could be the result of a perception that women with unfavorable characteristics, like younger age and high-risk tumors, don’t do as well with BCT.
The investigators noted that some differences in disease burden at baseline could have contributed to the findings.
"Interestingly, for every cause of mortality that we evaluated, women who had mastectomy were more likely to die within 3 years of their breast cancer diagnosis than women who chose BCT. Based on these findings, it is reasonable to infer that the mastectomy group was likely to have a greater burden of nonfatal comorbidities at presentation, and that this factor may well have influenced surgical decision-making. Nevertheless, this factor alone cannot account for why women with mastectomy had lower [disease specific survival] after adjusting for age and tumor characteristics," Dr. Hwang and her associates said.
Based on the strong associations with survival, "these findings support the notion that BCT, when combined with radiation, confers at least equivalent and perhaps even superior survival to mastectomy as definitive breast cancer treatment," they said.
The National Cancer Institute funded the study. Dr. Hwang had no financial disclosures.