Older women with estrogen receptor (ER)-negative metastatic breast cancer have a 39% lower risk of all-cause mortality if they receive chemotherapy within 6 months of their diagnosis, according to the results of a population-based study. Chemotherapy also extends their median survival by approximately 7 months.
“These findings reflect chemotherapy use outside of the clinical trial setting and have important clinical and policy implications,” commented Myra Schneider, PhD, with the University of Maryland in Baltimore.
They said that their study is notable for its focus on “the rapidly growing population of older women at greatest risk for a breast cancer diagnosis and most in need of treatment guidelines.”
Schneider and her team examined the survival benefit associated with chemotherapy in women drawn from the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) cancer registries. They decided to restrict their analysis to women aged ≥66 years in order to have a year of Medicare claims, which would allow them to determine preexisting comorbidity at the time of the breast cancer diagnosis. All participants had been diagnosed with stage IV ER-negative breast cancer between 1999 and 2005. The analysis excluded individuals who were enrolled in a health maintenance organization (HMO) in the 12 months before and during the month of their diagnosis.
Schneider and associates observed that while clinical studies have shown a favorable effect of various chemotherapy regimens on survival in patients with breast cancer, recommendations for the use of chemotherapy in older patients with breast cancer have been less clear-cut than those in younger patients. The main reason that chemotherapy guidelines are less definitive in older patients is the lack of empirical data that can be used to formulate guidelines in this population. In short, older women are grossly underrepresented in studies of cancer treatments.
The need for standards of care for older patients with breast cancer is becoming increasingly urgent, they added. More than half of all new breast cancers in the United States occur in women aged ≥65 years, and 30% occur in women aged ≥70 years.
The authors also called for increasing emphasis on improving outcomes in women with ERnegative tumors. These women have fewer treatment options because hormonal therapies such as tamoxifen and aromatase inhibitors are believed to be ineffective in ER-negative breast cancer.
More than half of all new breast cancers in the United States occur in women aged ≥65 years, and 30% occur in women aged ≥70 years.
Of 1519 ER-negative women diagnosed with metastatic breast cancer in the present analysis, 494 (33%) received chemotherapy within 6 months of their diagnosis. Chemotherapy was associated with a statistically significant survival benefit (hazard ratio = 0.61; 95% confidence interval, 0.54-0.70)
The median survival time was 5 months in women who did not receive chemotherapy and 12 months in women who received chemotherapy (P
<.001). The analysis also showed that age did not modify the survival effect of chemotherapy, with women deriving similar benefit from chemotherapy at all ages.
Schneider and team emphasized that their findings cannot be extrapolated to younger women receiving chemotherapy for breast cancer or to women participating in Medicare HMOs. Also, because the use of administrative claims data were used to obtain treatment information, it may not have been possible to identify the use of therapies that were not covered by Medicare.
Schneider M, Zuckerman IH, Onukwugha E, et al. Chemotherapy treatment and survival in older women with estrogen receptor-negative metastatic breast cancer: a population-based analysis. J Am Geriatr Soc. 2011;59(4):637-646.