Breast-Conserving Therapy Shows Survival Benefit Over Mastectomy in Patients With Early-Stage Hormone Receptor–Positive Disease
When factoring in what is now known about breast cancer biology and heterogeneity, breast-conserving therapy may offer a greater survival benefit over mastectomy to women with early-stage, hormone receptor–positive disease, according to research from The University of Texas MD Anderson Cancer Center. The study findings defy the conventional belief that the two treatment interventions offer equal survival, and show the need to revisit some standards of breast cancer practice in the modern era.
The research was presented at the 2014 Breast Cancer Symposium by Catherine Parker, MD, formerly a fellow at MD Anderson, now at the University of Alabama at Birmingham (Abstract 60).
In the 1980s, both U.S.-based and international randomized clinical studies found that breast-conserving therapy and mastectomy offered women with early-stage breast cancer equal survival benefit. However, those findings come from a period in time when very little was understood about breast cancer biology, explained Isabelle Bedrosian, MD, Associate Professor of Surgical Oncology at MD Anderson.
“Forty years ago, very little was known about breast cancer disease biology—such as subtypes, differences in radiosensitivities, radioresistances, local recurrence, and metastatic potential,” explained Dr. Bedrosian, the study’s senior author. “Since then, there’s been a whole body of biology that’s been learned—none of which has been incorporated into patient survival outcomes for women undergoing breast-conserving therapy or a mastectomy.
“We thought it was important to visit the issue of breast-conserving therapy vs mastectomy by tumor biology,” she continued.
Study Details
The researchers hypothesized that they would find that patients’ surgical choice would matter and impact survival with tumor biology considered.
For the retrospective, population-based study, the researchers used the National Cancer Database (NCDB), a nationwide outcomes registry of the American College of Surgeons, the American Cancer Society, and the Commission on Cancer that captures approximately 70% of newly diagnosed cases of cancer in the country. They identified 16,646 women in 2004 to 2005 with stage I disease who underwent mastectomy, breast-conserving surgery followed by 6 weeks of radiation (“breast-conserving therapy”), or breast-conserving surgery without radiation (“breast-conserving surgery”). Dr. Bedrosian noted that it was important that the study focused solely on women with stage I disease in order to keep the study group homogeneous and because in this cohort few would be ineligible for breast-conserving therapy.
Since estrogen receptor and progesterone receptor data were available and HER2 status was not, the researchers categorized the tumors as estrogen receptor– or progesterone receptor–positive (hormone receptor–positive), or both estrogen receptor– and progesterone receptor–negative (hormone receptor–negative). Patients were rigorously matched using propensity score for a broad range of variables, including age, receiving hormone therapy, and/or chemotherapy, as well as type of center where patients were treated and comorbidities.
Survival Results
Of the 16,646 women, 1,845 (11%) received breast-conserving surgery; 11,214 (67%) received breast-conserving therapy, and 3,857 (22%) underwent a mastectomy. Women who had breast-conserving therapy had superior survival to those who had a mastectomy or breast-conserving surgery—the 5-year overall survival was 96%, 90%, and 87%, respectively.
After adjusting for other risk factors, the researchers found an overall survival benefit for breast-conserving therapy compared to breast-conserving surgery and mastectomy. In a matched cohort of 1,706 patients in each arm, the researchers observed an overall survival benefit with breast-conserving therapy over mastectomy in the hormone receptor–positive subset but not in the hormone receptor–negative subset.
Retrospective Study
While provocative, Dr. Bedrosian cautioned that the findings are not practice-changing, as the study is retrospective. Still, the research complements other recent studies that showed breast-conserving therapy was associated with a survival benefit compared to mastectomy. Also, she points to the delivery of radiation therapy as the possible driver of the overall survival benefit.
“We’ve historically considered surgery and radiation therapy as tools to improve local control,” said Dr. Bedrosian. Yet recent studies suggest that there are survival-related benefits to radiation in excess of local control benefits. Therefore, radiation may be doing something beyond just helping with local control. Also, we know hormone receptive–positive tumors are much more sensitive to radiation, which could explain why we found the survival benefit in this group of patients.”
As follow-up, Dr. Bedrosian and her team hope to mine the randomized controlled trial findings from the 1980s, matching those cohorts to current NCDB patients to see if a similar survival benefit could be observed.
“While retrospective, I think our findings should give the breast cancer community pause. In the future, we may need to reconsider the paradigm that breast-conserving therapy and mastectomy are equivalent,” she said. “When factoring in what we know about tumor biology, that paradigm may no longer hold true.”
The study was institutionally funded. For full disclosures of the study authors, view the study abstract at abstracts.asco.org.
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®.
