| HOME | HELP | CONTACT US | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Breast Cancer |
aDepartment of Breast Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA; bNational Institutes of Health, Bethesda, Maryland, USA; cSealy Center on Aging, The University of Texas Medical Branch at Galveston, Galveston, Texas, USA
Key Words. Breast cancer • Elderly • Metastatic
Correspondence: Correspondence: Sharon Giordano, M.D., M.P.H., 1515 Holcombe Boulevard, Box 1354, Houston, Texas 77030, USA. Telephone: 713-792-2817; Fax: 713-794-4385; e-mail: sgiordan{at}mdanderson.org
Received October 18, 2007; accepted for publication March 24, 2008.
Disclosure: S.H.G. is supported by NIH 1K07 CA 109064–04. The funding sources had no role in the study design, conduct, data analysis, or manuscript preparation. No potential conflicts of interest were reported by the authors, planners, reviewers, or staff managers of this article.
This article is available for continuing medical education credit at CME.TheOncologist.com
![]()
Learning Objectives
Top
Learning Objectives
Abstract
Introduction
Methods
Results
Discussion
Author Contributions
Acknowledgments
References
After completing this course, the reader will be able to:
| ABSTRACT |
|---|
|
|
|---|
Methods. Patients were identified from the Surveillance, Epidemiology, and End Results–Medicare database who were aged
65 years and were diagnosed with invasive breast cancer in 1995–2002. Healthcare Common Procedure Coding System codes were used to identify patients treated with pamidronate and zoledronic acid. Descriptive statistics were used to describe patterns of use. Multivariate analyses were performed to determine the predictors of bisphosphonate use.
Results. In total, 55,864 women with breast cancer were included, with 307,467 person-years of follow-up. Overall, 1.26% of women with all stages of breast cancer received i.v. bisphosphonates. In 2004, 2% of all breast cancer patients and 32% of patients with distant stage disease received bisphosphonates. Approximately two thirds of patients treated with bisphosphonates received zoledronic acid and one third received pamidronate in 2004. Multivariate analyses showed that patients who were
75 years old were less likely to receive bisphosphonates (75–79 years versus 65–69 years: odds ratio [OR], 0.81; 95% confidence interval [CI], 0.70–0.93; 80+ years versus 65–69 years: OR, 0.49; 95% CI, 0.42–0.57). The use of bisphosphonates dramatically increased over time. The majority of living patients were continued on i.v. bisphosphonates once started (83% at 1 year, 64% at 3 years, 50% at 5 years), but the median survival time after initiation of i.v. bisphosphonates was only 21 months.
Conclusions. i.v. bisphosphonates appear to be underused in patients with metastatic breast cancer, particularly among those patients >75 years of age.
| INTRODUCTION |
|---|
|
|
|---|
i.v. bisphosphonates, such as pamidronate or zoledronic acid, inhibit osteoclastic absorption of bone and are used to prevent complications of bone metastases. Randomized clinical trials have compared patients treated with pamidronate with those given placebo and have shown that pamidronate reduces the risk for skeletal events, delays the time to skeletal events, and reduces pain among women with metastatic breast cancer to the bone [5–8]. Zoledronic acid has been compared with pamidronate and is at least as effective as pamidronate in preventing skeletal events [9–11]. The American Society of Clinical Oncology (ASCO) guidelines, which were originally published in 2000 and updated in 2003, recommend that women with evidence of metastatic bony destruction receive i.v. pamidronate or zoledronic acid every 3–4 weeks until there is a substantial decline in the patient's performance status [12, 13].
To our knowledge, very limited data have been published on patterns of bisphosphonate use. It is unknown whether the majority of women with metastatic breast cancer are receiving bisphosphonates or how long such therapy is continued after initiation. In this study, we present data on patterns of bisphosphonate use in a population-based cohort of older women with breast cancer.
| METHODS |
|---|
|
|
|---|
65 years [15]. SEER subjects were matched with Medicare's master enrollment file, using the method described by Potosky et al. [15] to create the SEER–Medicare database.
Study Population
The study population included women aged
65 years who were diagnosed with breast cancer in 1995 through 2002. Patients were excluded if the breast cancer diagnosis was not the patient's first cancer or if the histology was not confirmed. Patients without full coverage of both Medicare A and B for 1995–2004 were excluded, unless coverage was lost as a result of death. Women who belonged to a health maintenance organization were also excluded, because their claims data would be incomplete. Cases from Greater California, Kentucky, Louisiana, and New Jersey were excluded because those registries did not become part of the SEER program until 2000. All patients who were known to have received i.v. bisphosphonate treatment prior to their cancer diagnosis were also excluded from the study cohort.
The Healthcare Common Procedure Coding System drug administration codes J2430 (pamidronate) and J3487 (zoledronic acid) were used to identify patients who received i.v. bisphosphonate therapy during the period from January 1, 1995, to December 31, 2004. Patient demographic and tumor characteristics, such as age, ethnicity, marital status, census tract level social economic variables for education and poverty, tumor stage, and year of diagnosis, were obtained from the SEER–Medicare Patient Entitlement and Diagnosis Summary File. Medicare claims were available through December 2004.
Statistical Analysis
Among patients who met the eligibility criteria for this study, the prevalence of bisphosphonate use was calculated per person-year of follow-up for all patients and for those with metastatic disease. A univariate generalized estimating equation (GEE) method was used to calculate a p-value for the prevalence of bisphosphonate use for each covariate. We calculated the percentage of patients receiving i.v. bisphosphonates for each calendar year in 1995–2004 among all patients and among patients with distant stage disease.
A multivariate analysis was performed to determine the relationship between the covariates and bisphosphonate use. Annual bisphosphonate use was recorded starting from the diagnosis year and ending in the year of death or in 2004. Multiple logistic regression, implemented with a GEE method in order to account for multiple observations per individual, was performed to measure a dichotomous outcome of receiving bisphosphonate treatment or not, while adjusting for covariates. Because bisphosphonate use increased over time, an autoregressive correlation structure (first order) was specified in this model. The following covariates were included: age at diagnosis (categorical: 65–69 years, 70–74 years, 75–79 years, or
80 years), ethnicity (white, black, Hispanic, or other), marital status, census tract poverty level, census tract education level, historic stage (in situ, localized, regional, distant, or unstaged), bone metastases (no or yes), SEER region, and calendar year. For the census tract variables of poverty and education, quartiles were calculated in increasing order. The categories for percentage of persons
25 years of age with <12 years of education were 0%–7.76%, 7.77%–13.67%, 13.68%–21.29%, 21.3%–100%, and unknown. The categories for percentage of residents living below the poverty level were 0%–3.82%, 3.83%–6.74%, 6.75%–11.89%, 11.9%–87.17%, and unknown. Census data from the 2000 files were supplemented with 1990 files if missing or unknown information was found.
Among patients who had claims for i.v. bisphosphonate use, we calculated the proportion of patients who continued bisphosphonates in subsequent years using the method of Kaplan and Meier. Dose was calculated such that claims for 4 mg of zoledronic acid and 90 mg of pamidronate were considered to be an equivalent single dose. The mean numbers of doses were calculated for patients by length of follow-up. The survival experience of patients from the first dose of bisphosphonates was calculated using the method of Kaplan and Meier. SAS software (SAS Institute, Inc., Cary, NC) was used for all statistical analyses. All statistical tests were two-sided.
The study was reviewed by the institutional review board (IRB) and was granted an exemption from IRB approval under Category 4 of the Code of Federal Regulations, because the data are without identifiers.
| RESULTS |
|---|
|
|
|---|
|
|
80 years of age (Fig. 1B).
|
75 years old were significantly less likely to receive i.v. bisphosphonates, after adjustment for covariates including disease stage and presence of bone metastases and after accounting for length of follow-up. Patients living in census tract areas characterized by a lower educational level were also less likely to receive i.v. bisphosphonates. Consistent with the univariate findings, the use of bisphosphonates dramatically increased over time.
|
|
|
| DISCUSSION |
|---|
|
|
|---|
In the multivariate models, we found that bisphosphonate use significantly declined with age. Patients
80 years of age were 0.60 times less likely to be treated with bisphosphonates than women aged 65–69 years. These findings are consistent with previous studies that have documented less aggressive treatment of older women across many different modalities of therapy [16–21]. However, given the high prevalence of osteoporosis and osteopenia among older women, the lower use of bisphosphonates is somewhat surprising. It is possible that concerns over renal toxicity among older women who have poorer renal function results in the lower use of bisphosphonates in the elderly.
In this study, we were also interested in exploring the length of therapy and cumulative dose of bisphosphonates among women who had been started on i.v. bisphosphonates. ASCO guidelines recommend that therapy be continued as long as the patient has a good performance status [12, 13]. However, the optimal length of therapy is under debate. The clinical trials that established the benefits of bisphosphonates treated patients for 12–24 months [6, 7, 22–24]. Recently, potential toxicities of bisphosphonates, such as osteonecrosis of the jaw and renal dysfunction, have increasingly been recognized and are thought to be dose-related [25–28]. Therefore, concerns have been raised about continuing i.v. bisphosphonates indefinitely, because an additional incremental benefit has not been proven but the toxicities appear to increase. In our study, we found that the majority of women were continued on bisphosphonates for the remainder of their lives. Our analysis of cumulative dose by length of follow-up indicates that patients tended to receive bisphosphonates less frequently than every 3–4 weeks, particularly patients who continued on bisphosphonates for years (i.e., patients still on bisphosphonates at 24 months had received a mean of 17 doses).
The use of zoledronic acid versus pamidronate also increased over the years in this study. Although ASCO guidelines recommend either zoledronic acid or pamidronate, zoledronic acid has the advantage of a shorter infusion time (15 minutes versus 90 minutes). In addition, some data suggest that zoledronic acid may have superior efficacy in breast cancer patients when compared with pamidronate [10].
Our study has some limitations. First, it was conducted using claims data. From claims data, we could not identify patients with bone metastases who were clinically fit to receive i.v. bisphosphonates. We were able to reliably evaluate all patients with breast cancer or patients with distant disease at diagnosis based on SEER staging. Our study is also limited by the lack of a billing code for zoledronic acid in 2001 and 2002, after the drug was approved by the FDA and available for use. This resulted in an underestimate of i.v. bisphosphonate use in those 2 years. Finally, some of the bisphosphonate use could have been for treatment of hypercalcemia of malignancy, although hypercalcemia is uncommon without bone involvement.
In conclusion, we present data from a large population-based cohort of women with breast cancer. The use of i.v. bisphosphonates was lower than expected. Our data suggest that these highly effective supportive care medications are underused in older women with breast cancer. However, the majority of patients that are started on bisphosphonates are usually continued on bisphosphonates throughout their lifespan, consistent with guideline recommendations. Further research is needed to confirm our findings and to develop interventions to increase the use of bisphosphonates, so that skeletal complications in women with metastatic breast cancer can be minimized.
| AUTHOR CONTRIBUTIONS |
|---|
|
|
|---|
Financial support: Sharon H. Giordano
Administrative support: Sharon H. Giordano
Provision of study materials or patients: Sharon H. Giordano
Collection/assembly of data: Sharon H. Giordano
Data analysis and interpretation: Sharon H. Giordano, Shenying Fang, Zhigang Duan, Yong-Fang Kuo, Gabriel N. Hortobagyi, James S. Goodwin
Manuscript writing: Sharon H. Giordano, Shenying Fang, Zhigang Duan
Final approval of manuscript: Sharon H. Giordano, Shenying Fang, Zhigang Duan, Yong-Fang Kuo, Gabriel N. Hortobagyi, James S. Goodwin
| ACKNOWLEDGMENTS |
|---|
|
|
|---|
| REFERENCES |
|---|
|
|
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | CONTACT US | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| THE ONCOLOGIST | STEM CELLS | CME | ALPHAMED PRESS JOURNALS |