The Cost of Treating Skeletal-Related Events in Patients With Prostate Cancer

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The American Journal of Managed Care, May 2008 - Theme Issue, Volume 14, Issue 5

The analysis examines the annual economic effect of medically treating patients with prostate cancer and subsequent bone metastases.

Objectives

: To examine the economic burden of skeletal-related events (SREs) and to assess the frequency of different types of SREs in this population.

Study Design

: Retrospective claims analysis.

Methods

: Data were obtained from i3’s Lab Rx Database from May 1, 2000, through March 31, 2005. Patients included had at least 2 claims with a diagnosis of prostate cancer, at least 2 subsequent claims with a diagnosis of bone metastasis, and at least 1 SRE on or after the date of the initial diagnosis of bone metastasis. Descriptive statistics for 342 patients who fit all inclusion and exclusion criteria are provided, along with Kaplan-Meier curves, which were used to estimate annual costs, adjusting for the censoring of the data.

Results

: Patients most frequently had radiation therapy (89%), followed by pathologic fracture (23%) and bone surgery (12%). Among patients diagnosed as having at least 1 SRE, 78% experienced 1 type of SRE, 17% had 2 types of SREs, and 5% had 3 or more distinct types of SREs. The mean costs associated with SREs in the year after the initial diagnosis of an SRE, adjusted for the censoring of the data, was $12,469, with the highest costs associated with radiation therapy ($5930), followed by pathologic fracture ($3179) and bone surgery ($2218).

Conclusion: This study of patients with prostate cancer and bone metastases revealed that the annual economic effect of medically treating SREs for these patients was $12,469.

(Am J Manag Care. 2008;14(5):317-322)

Prostate cancer has the highest incidence of any nonskin cancer in the United States, and bone metastasis is a common form of metastatic disease among patients with prostate cancer. Bone metastasis is complicated by the occurrence of skeletal-related events (SREs).

This research quantifies the costs of SREs among patients with prostate cancer and bone metastases. Results reveal that the mean annualized costs of SREs for this population was $12,469.

The research illustrates the relative frequency at which different types of SREs occur, with patients most likely to undergo therapeutic radiology or to have a pathologic fracture.

Prostate cancer has the highest incidence of any nonskin cancer in the United States and is the second leading cause of cancer-related deaths among US men.1-3 It was projected that 218,890 new cases of prostate cancer would be identified in the United States in 2007 and that an estimated 27,050 men would die of the disease.4

Bone metastasis is a common form of metastatic disease among patients with prostate cancer. Yuen et al5 report that 80% of men with metastatic disease have bone metastasis, and others report percentages between 65% and 70%.6,7 In addition, as many as 20% of men who are newly diagnosed as having prostate cancer already have bone metastases.8 Bone metastases are complicated by significant morbidity, including skeletal-related events (SREs), which are local irreversible changes and include pathologic fracture, bone surgery, radiation therapy to the bone, and spinal cord compression.9-12 These events negatively affect quality of life10,13,14 and present a challenge for the goals of palliative therapy, which include managing these patients’ pain, preventing further deterioration, and preserving quality of life.15-18

Although the humanistic burden of SREs is well documented, little research has focused on the economic effects of medically treating SREs. To our knowledge, only one study19 has looked specifically at the costs of SREs in patients with prostate cancer and bone metastases; the sample of patients in the analysis was small (n = 28), and the costs were based on care in The Netherlands. However, studies of SREs among patients with lung cancer20 and breast cancer9,21 have consistently shown SREs to be common and costly.

In the present study, the objectives were to elucidate further the US costs associated with SREs among patients with prostate cancer and bone metastases and to determine the relative frequency at which the different types of SREs occur. To this end, we conducted a retrospective analysis using a large US health insurance claims database to examine the incidence and costs associated with SREs among patients with bone metastases secondary to prostate cancer.

METHODS

Table 1

Half of all patients with at least 2 claims for prostate cancer (n = 342) and at least 2 claims for bone metastasis (n = 878) experienced 1 or more SREs (n = 435). For men who had at least 1 SRE, 87% were identified as having had an SRE within 1 year of their initial diagnosis of bone metastasis. Their mean age was 68.1 years, with most men residing in the South (49%) or in the Midwest (32%) (), which is consistent with the population in the database. Most patients were commercially insured (66%), and the most common type of insurance was a health maintenance organization (52%). An examination of prior resource utilization, the severity score by Charlson et al,27 and comorbidities revealed that, as expected, patients in this study were severely ill. For example, the mean (SD) Charlson severity score was 1.43 (1.55), and the patients had been hospitalized in the 6 months before the index date for a mean of 6.6 days and had a mean number of office visits of 14.2. In addition, 37% of patients included in the study had also been diagnosed as having cardiovascular disease, and 16.1% had been diagnosed as having comorbid diabetes mellitus.

Figure 1

Most patients received radiation therapy (89%), as shown in . Approximately 23% experienced a pathologic fracture, and 12% had bone surgery. Some SREs occurred in clusters, meaning that it was possible that someone had a fracture that required bone surgery, and in this case both events are captured as separate types of SREs.

Figure 3

shows the Kaplan-Meier estimated probability of continuation in the database (survival proxy) for the population from the time of initial diagnosis of an SRE. After 2 years, the proxy survival rate was 16%, and the median proxy survival was approximately 8.5 months.

As a test of the robustness of the results, we reexamined the analysis, omitting service from a radiation oncologist as a criteria in defining therapeutic radiology. Although the percentage of individuals with an SRE identified as having therapeutic radiology declined from 89% to 78%, the general results were consistent with those reported herein. For example, this analysis found 1-year costs associated with an SRE to be $12,649, while omitting service from a radiation oncologist reduces this amount to $12,007. In addition, this analysis estimated the 2-year survival rate to be 15%, while the reexamined subset of data resulted in an estimated 2-year survival rate of 16%.

DISCUSSION

Many patients with prostate cancer metastasized to the bone experience SREs. In addition to physical adversity associated with these events, these patients will also incur high costs for medical treatment of the SREs. The findings of this analysis suggest that safe measures to mitigate or prevent SREs have the potential to yield cost offsets. Although earlier studies looking at costs of SREs in cancer paients9,20 have come to similar conclusions, this analysis uses the largest sample of patients with prostate cancer, bone metastases, and SREs examined to date, to our knowledge.

Acknowledgment: We thank Patricia Platt for her help with the manuscript.

Author Affiliations: HealthMetrics Outcomes Research, LLC (MJL), Groton CT; Department of Global Health Economics (BLB, DJH) and Department of Clinical Development (SJ), Amgen Inc, Thousand Oaks, CA.

Funding Source: This study was funded by Amgen, Inc.

Author Disclosure: Drs Lage and Jun consult for Amgen and received payment for their involvement in the preparation of this manuscript. Drs Barber and Harrison are employees of Amgen and report owning stock in that company.

Authorship Information: Concept and design (BLB, DJH); acquisition of data (BLB); analysis and interpretation of data (MJL,BLB, DJH, SJ); drafting of the manuscript (MJL, BLB, SJ); critical revision of the manuscript for important intellectual content (MJL, BLB, DJH, SJ); statistical analysis (MJL); obtaining funding (BLB); administrative, technical, or logistic support (BLB); and supervision (BLB).

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