SEER Study: Less Surgery, Longer Breast Cancer Survival

Nick Mulcahy

January 16, 2014

Women with early-stage invasive breast cancer who undergo breast-conserving therapy (BCT) have a higher rate of disease-specific survival than those who undergo mastectomy, according to an analysis published online January 15 in JAMA Surgery.

This is the second large observational study in the past year to show a disease-specific survival benefit with BCT, which consists of lumpectomy plus radiation.

However, experts caution that, as with all observational studies, the evidence is not as strong as that from a prospective randomized trial.

Nonetheless, the 10-year breast-cancer-specific survival rates were 94% for patients who underwent BCT, 90% for those who underwent mastectomy alone, and 83% for those who underwent mastectomy plus radiation (P < .001), report the investigators, led by Shailesh Agarwal, MD, from the University of Michigan Medical School in Ann Arbor.

"Many women have the false idea that mastectomy is superior to breast-conserving therapy in terms of survival," Kandace McGuire, MD, a surgical oncologist from Magee-Womens Hospital of the University of Pittsburgh Medical Center, told Medscape Medical News.

This study will help clinicians counsel patients, said Dr. McGuire, who was not involved with the research.

The researchers looked at 132,149 patients in the Surveillance, Epidemiology, and End Results (SEER) database who underwent treatment for early-stage disease (tumor size, ≤4 cm; ≤3 positive lymph nodes) from 1998 to 2008.

Overall, 70% of the patients were treated with BCT, 27% were treated with mastectomy alone, and 3% were treated with mastectomy plus radiation.

These disease-specific survival findings are in line with findings from a large observational study of patients with early-stage disease in California. That study, by E. Shelley Hwang, MD, from Duke University in Durham, North Carolina, had a median follow-up of 9 years (Cancer. 2013;119:1402-1411).

"I am so happy to see this study, which completely confirms our earlier findings," said Dr. Hwang. "It is a reassuring message for women [who chose or are considering BCT]," she told Medscape Medical News.

It is a reassuring message for women.

Dr. Agarwal and his colleagues point out that the less-invasive BCT was recommended as the treatment of choice for stage I or II disease by the National Institutes of Health (NIH) in 1990.

The NIH recommendation was based on several major randomized trials that showed similar survival rates for BCT and mastectomy. However, those trials are now 40 years old, necessitating more contemporary analyses, the investigators assert.

Dr. Agarwal's team used multivariate analysis to account for possible imbalances in demographic and oncologic data among the treatment groups. They adjusted for variables such as the number of positive lymph nodes (0 vs 1 to 3), tumor size (≤2 cm vs >2 to 4 cm), estrogen-receptor and progesterone-receptor status, and tumor grade.

They found that women undergoing BCT had a higher survival rate than those undergoing mastectomy alone (hazard ratio [HR], 1.31; P  <  .001) or mastectomy plus radiation (HR, 1.47; P <  .001).

Dr. McGuire noted that the study by Dr. Hwang's team and this study are part of a growing body of evidence indicating that BCT is "equivalent, if not superior, to mastectomy in terms of breast-cancer-specific survival."

Limitations Are Considerable

Dr. McGuire's qualification that BCT might only be equivalent to mastectomy comes in part from her reservations about data from SEER and similar databases.

"You don't get a lot of granularity with SEER," she pointed out. Patients with multicentric or more complicated disease, for example, might have been more likely to choose mastectomy. The higher mortality seen with mastectomy could be the result of such an undisclosed oncologic detail.

The investigators acknowledge as much. "Our study is also limited by lack of tumor biology information such as lymphovascular invasion, extracapsular invasion, and size of nodal metastases, which are not reliably reported by the SEER database, and may portend a poorer prognosis," they write.

Dr. McGuire's reservations about the findings are also rooted in her own research.

In a previous study, she and her colleagues studied the choice of breast cancer surgery, and found that lower socioeconomic status is "strongly associated" with mastectomy (Ann Surg Oncol. 2009;16:2682-2690).

The implication is that patients with less income and social clout tend to live shorter lives than their more privileged counterparts.

Furthermore, BCT is "typically" the treatment choice for patients with higher levels of education, greater access to adjuvant therapies, more money, and convenient locales (cities and suburbs) near healthcare facilities, she said. "These patients also tend to be more compliant with therapies," Dr. McGuire explained.

Because of the vagaries of observational data, Dr. Hwang and her colleagues were also cautious when describing their findings. The superior disease-specific survival results they found with BCT "provide confidence" that BCT is "an effective alternative" to mastectomy, they conclude.

The authors and Dr. McGuire have disclosed no relevant financial relationships. Dr. Hwang reports financial ties with Genomic Health and Merck.

JAMA Surg. Published online January 15, 2014. Abstract


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