E. Shelley Hwang, MD, MPH
A large, population-based study of women who opted for lumpectomy and radiation rather than mastectomy to treat their early-stage breast cancer has found that women who chose the breast-conserving option had both better disease-specific survival (DSS) and overall survival (OS) compared with their mastectomy counterparts.
Although clinical trial results have shown that survival outcomes are similar for early-stage breast cancer treated with breast-conserving therapy with radiation (BCT) or mastectomy, recent reports show increased interest in mastectomies, especially among younger women with in situ disease living in more affluent regions of the country. In this study, Duke University investigators wanted to find out whether comparable survival findings derived from clinical trials might be generalized to breast cancer patients outside the clinical trial setting.
Using data from the California Cancer Registry, researchers identified 112,154 women with stage I-II invasive breast cancer who were treated with either BCT (n = 61,771) or mastectomy without radiation (n = 50,383) between 1990 and 2004, and who had at least 5 years of follow-up. Patients whose hormone receptor status was borderline or unknown were not eligible. Human epidermal growth factor receptor status results were not uniformly available prior to 2006, and thus were not included in this study, which followed patients for a median of 9.2 years.
Across the entire cohort, 31,416 deaths occurred during the study period, 39% of which were attributable to breast cancer. Over 5 years, OS was 89.3% and DSS was 94.4%.
Four subgroups within the cohort were identified based on age and hormone receptor (HR) status, as follows: age ≥50, HR-negative; age ≥50, HR-positive; age <50, HRnegative; and age <50, HR-positive. Using Cox multivariate analysis techniques, the researchers found that when compared with mastectomy, BCT was associated with improved OS across all of these subgroups. Women aged ≥50 with HR-positive disease achieved the greatest survival benefit from BCT with a 19% lower overall mortality (hazard ratio = 0.81; 95% CI, 0.79-0.84). Those <50 years of age with HRpositive tumors experienced the smallest survival benefit from BCT (hazard ratio = 0.93; 95% CI, 0.86-0.99).
For DSS, women aged ≥50 with HR-positive breast cancer also derived the greatest benefit from BCT with a 13% lower breast cancer mortality compared with those who had mastectomies (hazard ratio = 0.87; 95% CI, 0.82-0.92). Minimal or no significant benefit for BCT over mastectomy was found in the other subgroups.
Survival was also compared using a Kaplan-Meier estimator, and OS and DSS rates again favored the BCT approach. The benefit of BCT was seen in both younger and older women and in those with HR-positive and HR-negative disease; OS was better even among those with T2 tumors.
The researchers noted that they did not anticipate the finding that patients who underwent mastectomy would have “significantly lower OS and breast cancer–specific survival than women who underwent BCT, even after adjusting for tumor grade, proportion of positive nodes, race, socioeconomic status (SES), tumor size, age at diagnosis, and year of diagnosis.”
A potential limitation of the study is that cancer registries do not capture certain information, such as coexisting comorbidities and detailed pathologic data, as well as biases on the part of providers and patients that could impact treatment decisions; however, the researchers noted that they did not believe these factors would yield a bias large enough to override the influence of variables that were included in their analysis, including age, tumor size, race, SES, and node status.
“Our findings are observational but do suggest the possibility that women who were treated with less invasive surgery had improved survival compared to those treated with mastectomy for stage I or stage II breast cancer,” said E. Shelley Hwang, MD, MPH, chief of Breast Surgery at Duke Cancer Institute and the study’s lead author.
Hwang ES, Lichtensztajn DY, Gomez SL, et al. Survival after lumpectomy and mastectomy for early stage invasive breast cancer: the effect of age and hormone receptor status [published online ahead of print January 28, 2013]. Cancer. doi:10.1002/cncr.27795.