Influence of surgical and treatment choices on the cost of breast cancer care

Transcription

1 Eur J Health Econom : DOI /s Original Papers C. J. Bradley 1 C. Given 2 O. Baser 3 J. Gardiner 4 1 Department of Medicine, Michigan State University, East Lansing, Mich., USA 2 Department of Family Practice, Michigan State University, East Lansing, Mich., USA 3 Medstat 4 Department of Epidemiology, Michigan State University, East Lansing, Mich., USA Influence of surgical and treatment choices on the cost of breast cancer care Abstract We obtained medical claim files covering a period of 1 year prior to breast cancer diagnosis and the year following diagnosis for 204 women and estimated the cost of their treatment.we used log-linear regression controlling for age, comorbidity, physical functioning, and disease stage.to retransform the mean costs, we estimated separate smearing factors for surgical and adjuvant care types.the adjusted mean costs for breast cancer care ranged from $16,226 to $39,305 depending on the treatment provided with mastectomy being the least expensive option. Breast-conserving surgery (BCS) was more expensive because most women have multiple surgeries after the initial BCS and require adjuvant care. If the first surgery was a mastectomy, medical care use tends to return to precancer spending levels within a few months. Over one-half of the women in this study had multiple surgeries following diagnosis, leading to substantial costs and unknown morbidity. Keywords Breast cancer Treatment costs Cost of illness Cost analysis Two phenomena are occurring that make accurate prediction of medical care costs of interest to researchers, policy makers, and health care planners. The first is the aging of a large cohort of individuals born shortly after World War II. The second is the increased incidence of and treatment costs for chronic diseases such as cancer. Cancer is of particular interest since early detection methods are improving while treatment success has remained somewhat constant. As evidenced by the literature [5, 7, 10, 12, 18], the cost of cancer treatment has gained considerable attention. Often, studies approach cancer care cost estimation by segmenting the course of disease into phases that ignore specific treatment protocols. Disease phases are typically divided into the first 6 months after diagnosis, the last 6 or 12 months of life, and the time between the first and last intervals [4, 7, 10, 14, 15, 18]. In general, initial and terminal care phases are highest in cost compared to the continuing phase, with terminal care generally costing more than the initial phase. Studies such as these provide information on the burden of illness over a patient s lifetime, but are limited in their applications. The phases are a black box in terms of procedures and care provided during a particular phase. In addition, the relative contribution of specific surgical types and adjuvant care to total cost is unknown. The initial phase, for example, may contain various combinations of surgery, radiation, and chemotherapy. Some of these treatments are likely to slip into the continuing phase, such as second or third surgeries and chemotherapy courses. It is more useful to understand how initial treatment strategies, rather than phases, contribute to costs over the course of disease. For example, Barlow et al. [5] estimated the treatment cost of care for women with early stage breast cancer and found that costs varied significantly by surgical intervention and adjuvant therapy with mastectomy alone as the least costly intervention 1 year following breast cancer diagnosis. Subjects and methods We identify major components of breast cancer treatment by examining surgical and adjuvant care options applied to a cohort of women with incident cases of breast cancer. We then estimate their total cost of care 1 year following diagnosis. We differentiate between mastectomy alone, single breast conserving surgery (BCS), multiple BCS, BCS followed by mastectomy, and BCS followed by axillary node dissection. We also differentiate between adjuvant care options of radiation alone, chemotherapy alone, and combinations of radiation and chemotherapy. The extent to which these treatment strategies predict major Springer-Verlag 2003 Cathy J. Bradley Department of Medicine, B212 Clinical Center, Michigan State University, East Lansing, MI 48824, USA, Cathy.Bradley@ht.msu.edu 96 Eur J Health Econom

2 changes in costs over the course of 1 year following diagnosis was estimated, controlling for influences such as age, comorbidity, physical functioning, and disease stage. Our research questions were: (a) What are the costs of breast cancer during the year following diagnosis, and how do these costs vary by the numbers and types of surgical and adjuvant care options? (b) What are the main correlates of total cost? (c) Do medical care costs return to prior spending levels once treatment is complete? During the years 1994 through 1997, we recruited 222 women with incident cases of breast cancer from 24 Michigan community hospitals and their affiliated oncology settings. Patients were 65 years or older and within 2 weeks of initiating either radiation or chemotherapy. Approximately 68% of the women approached enrolled. In these communities, 90% of the breast cancers were detected at early stages as reported by the community population-based tumor registries. This compared very favorably with the 82% of the cases that were accrued at early stages for our study. Once patients were accrued, their Social Security numbers were sent to the Health Care Financing Administration (currently known as the Centers for Medicare and Medicaid Services) to obtain inpatient, outpatient, and physician supplier files for all patients. Each woman provided written consent for researchers to acquire their Medicare claim files and to review their medical records. In the United States, the Medicare program provides health insurance to nearly all persons aged 65 years or older and persons younger than 65 years entitled to disability insurance benefits and persons with endstage renal disease. Medicare Part A provides coverage for inpatient care and Medicare Part B provides coverage for physician services, outpatient services, and some skilled home health care. Medicare does not include skilled nursing home services or self-administered prescription drugs. For example, chemotherapy administered in inpatient or outpatient settings is covered by Medicare, but self-administered drugs, such as tamoxifen, are not covered and their costs are not present in the claim files. Of the 222 breast cancer cases enrolled, we confirmed an initial breast cancer surgical event (either BCS or mastectomy) in the Medicare claim files for 205 women. Claim files were not available for 8 cases because a match between their Social Security number and Medicare Health Insurance code was not possible. Nine cases were excluded due to incomplete surgical data and one case was excluded due to missing patient characteristics, leaving a final sample size of 204 women. Cases excluded were not statistically different in terms of patient and disease characteristics from the study sample. Patient information (e.g., age, race, education, income, marital status) was available through patient interviews.we collected data on the patient s symptoms (e.g., fatigue, nausea, vomiting, pain), comorbidities, and physical and mental functioning as measured by the Short Form-36 (SF-36) scale [16]. Comorbid conditions were assessed by questions from the Aging and Health in America Survey [1] that documents 15 diseases and health problems other than cancer such as diabetes, hypertension, and heart disease. Each chronic condition was recorded as a yes/no response and the affirmative responses were summed to create a comorbidity score. We also matched each patient s Social Security number to the Michigan Department of Community Health, Office of Vital Statistics Death Certificate Registry.All patients were confirmed to be alive 1 year or longer after breast cancer diagnosis. Disease stage was determined using the American Joint Committee on Cancer (AJCC) tumor nodes and metastasis (TNM) staging system [2] applied to pathological data obtained from an audit of patients medical records (AJCC Cancer Stage Manual 1997). Surgical procedures were identified through the Medicare claim file International Classification of Diseases, version 9 (ICD-9) and Current Procedural Technology (CPT) codes, and were reviewed by a breast cancer surgeon. BCS was classified as local excision and partial and subtotal mastectomies. Modified radical and radical mastectomies including bilateral, ipsilateral, and simple and extended mastectomies were classified as mastectomy.we used all ICD-9 and CPT codes available in the inpatient, outpatient, and physician supplier files to identify procedures [8, 17], including chemotherapy and radiation. Payments by Medicare were used as a proxy for direct medical care costs as opposed to billed charges. In general, charges inflate actual costs and are not an acceptable proxy for costs [11]. However, Medicare payments are related to charges through reimbursement formulas that are designed to reflect the underlying pattern of resource utilization [7]. Therefore we estimate costs based on payments as reported in the Medicare claim files, adjusted for inflation to 1997 prices by using the National Medical Care Price Index, Control variables We classified surgical procedures as mastectomy, single BCS, multiple BCS, and BCS followed by mastectomy and include axillary node dissection as a separate dummy variable. Sixty-seven women had either a second BCS or a mastectomy following an initial BCS. Adjuvant care was grouped into four categories: no chemotherapy or radiation, radiation only, chemotherapy only, and a combination of chemotherapy and radiation. Because past research suggests that a relationship exists between disease stage and age, and surgical and adjuvant care decisions [7, 10, 15], we controlled for stage (in situ/local, regional, and distant) and age in our analysis. Other patient characteristics available to us for analysis were comorbidities, symptoms, and physical functioning. Number of comorbidities was classified into two groups: fewer than two and two or more. An examination of the partial regression residual plots showed that a continuous specification of comorbidity was clearly inappropriate because the interval between number of comorbidities was nonlinear. We then examined different combinations of dummy variables in separate regression equations and used the F test to determine the relative contributions of the restricted and unrestricted models. Based on our analysis, we found two primary distinctions among women with less than two comorbidities and two or more comorbidities. We included continuous variables for number of symptoms and physical functioning score (0 100). In addition, following the example of Lipscomb et al. [13] where past medical care use was shown to predict future use, we included a continuous variable for a patients total Medicaid cost one and 3 months prior to diagnosis. Because these variables were skewed to the Eur J Health Econom

3 Original Papers Table 1 Patient characteristics Categorical variables N (%) Education Less than high school 37 (19%) High school 84 (41%) More than high school 82 (40%) Race White 194 (95%) Nonwhite 10 (5%) Stage at diagnosis In situ/local 130 (64%) Regional 60 (29%) Distant 12 (6%) Comorbid medical conditions >2 46 (23%) (77%) Living arrangements Alone 73 (36%) With spouse or other 133 (65%) Continuous variables Mean (SD), range Age (years) 73±5.24 (65 89) SF-36 physical functioning (3 months prior to diagnosis) 80±23 (10 100) Number of symptoms (6 8 weeks postdiagnosis) 7.31±4.20 (0 17) SF-36 Mental Health Functioning (3 months prior to diagnosis) 65±27 (0 100) Costs prior to diagnosis 1 month prior $758±1,301 ($0 10,698) 3 months prior $1,452±2,552 ($4, ,003) right, we entered them into the regression equations in their natural log transformation, adding 1 to observations equaling 0. Empirical estimation As often is the case with cost data, we found that treatment costs were skewed to the right; therefore we transformed the cost equations into a log linear scale. We retransformed the log costs by the use of smearing estimators [9]. The smearing estimator is the exponential of the expected response on the log-scale multiplied by the average of the exponentiated residuals [3, 9].Andersen et al. [3] improved upon this technique by developing heteroscedastic smearing estimators when the variance of the residual error was not constant. Following their example, we estimated separate smearing factors for surgical types and adjuvant care types to obtain appropriate standard errors for mean costs in the treatment groups. The relative effects of a surgical procedure (e.g., a single BCS relative to mastectomy alone) or adjuvant care regimen (e.g., radiation vs. no adjuvant care) on costs was estimated as the ratio of the predicted health care cost between surgical and adjuvant care types. An example using mastectomy and BCS is shown is below. where S is the smearing factor for each surgical and adjuvant care intervention [9] and X is the corresponding explanatory variable for mastectomy and BCS. We estimated confidence intervals of the cost prediction using the bootstrap technique [6]. Results Descriptive analysis As shown in Table 1, the patient population can be described as white, high school or better educated, married or living with someone, and in their middle-70s. Two-thirds of the patients were diagnosed with early stage cancer whereas approximately one-third of the patients were diagnosed with regional or distant disease. Most patients (77%) had two or more comorbidities and experienced some level of symptoms related to cancer treatment. Our patient sample was high functioning in terms of physical and mental health relative to the general population of United States women over the age of 65 years. We observed that in the months prior to cancer diagnosis, the average monthly Medicare payment had considerable variability. Some patients did not require any Medicare reimbursed services, whereas other patients incurred high expenses. The average monthly payment 1 month prior to diagnosis was $758, with a large standard deviation of $1,301 and range extending from $0 to $10,698. The median payment was $320. Similarly, in the 3 months prior to diagnosis the average payment was $1,452 (median $620), again, with a large standard deviation and wide range of payments ($0 $131,003). Considering the unadjusted means for the surgical interventions (Table 2), mastectomy was the least expensive option ($21,955), followed by a single BCS ($26,136) and a BCS followed by mastectomy ($22,790), with multiple BCS being the most expensive option ($30,319). Total Medicare payments 1 year following diagnosis is shown in the last row of Table 2. The mean total unadjusted cost of care was $25,153 for the year following a breast cancer diagnosis. Regression analysis Table 3 shows the results of the regression analysis predicting total cost of care the year following a breast cancer diagnosis. The first column of Table 3 shows the regression results with surgical procedures in the model and the last column of Table 3 shows how adjuvant care regimens contribute to medical costs. Used in conjunction with surgical types, much of the variability in costs of medical care for patients diagnosed with breast cancer was explained (adjusted R 2 =0.53). As shown in Table 3, the coefficient for physical functioning, while statistically significant is small in magnitude. 98 Eur J Health Econom

4 Table 2 Total mean cost of medical care by surgical intervention Intervention Unadjusted mean cost Mastectomy (n=42) $21,955±18,282 Single BCS (n=71) $26,136±16,181 Multiple BCS (n=34) $30,319±9,173 BCS + mastectomy (n=53) $22,790±13,671 All surgical types combined (n=204) a $25,153±15,140 a Includes patients with a BCS followed by axillary node dissection Severity measures, such as comorbid conditions and stage, have statistically significant and substantial positive effects on cost. In columns 1 and 2 of Table 3, having two or more comorbid conditions increase costs by 20% and 15%, respectively. Disease stage has a large positive, independent effect on costs. Compared to in situ or local stage cancer, regional stage increases total cost of care by 27%. Distant stage increases total costs by 46%. However, disease stage was no longer statistically significant once adjuvant care regimens were added to the model. In both specifications, an axillary node dissection added significant cost to medical care expenditures. Another variable of interest was health care expenditures 3 months prior to diagnosis. We show that for every dollar increase in costs in the 3 months prior to diagnosis, total costs increased by 8%. Once adjuvant care was added to the model, the coefficients for single and multiple BCS were no longer statistically significant compared to mastectomy. However, a BCS followed by a mastectomy increased total cost by 40%, independent of the effect of adjuvant care. Few of these patients (n=16) received adjuvant care after a mastectomy was performed. In the remaining rows of Table 3,we show the smearing factors for each surgical and adjuvant care intervention. It is more meaningful to think of treatment interventions in terms of their relative magnitude than simply interpreting their coefficients (these coefficients are shown in Table 3 for the interested reader). In Table 4, we used the smearing factors generated in Table 3 to compute the effect each intervention had on cost relative to either mastectomy alone or no adjuvant care. Multiple BCS increased total costs by 1.64 times compared to mastectomy alone. A single BCS followed by mastectomy was 1.21 times greater than a mastectomy alone. In our sample, 37% of the women required a mastectomy after their initial BCS. Patients least likely to receive adjuvant care were those whose first surgical procedure was a mastectomy whereas patients most likely to receive adjuvant care were those who receive BCS. As one would expect, the type and intensity of adjuvant care had a large, statistically significant positive effect on total costs for the year following diagnosis. Combinations of radiation and chemotherapy were much greater (2.98 times greater) than a surgical intervention that was not followed by adjuvant care. Our next step was to retransform the costs from the regression equation into a mean cost of care for the typical patient in our sample receiving various combinations of surgery and adjuvant care. We used the smearing procedure to recover the means for these patients and show the results in Tables 5 and 6. Table 5 provides the mean total adjusted costs based on surgical type alone and Table 6 provides the adjusted costs based on the expanded model where adjuvant therapy regimens were added. In Table 5 the mean costs for the year following a breast cancer diagnosis for patients receiving mastectomy alone was $21,274 [95% confidence inter- Table 3 Log-linear regression model using surgical and adjuvant care options Surgical interventions only Surgical + adjuvant care interventions Independent variable Log total costs Log total costs Physical functioning (0.002)* (0.001)*** 2+ comorbid conditions 0.18 (0.08)** 0.13 (0.05)*** Regional stage 0.24 (0.08)*** 0.05 (0.06) Distant stage 0.38 (0.19)** 0.07 (0.12) Log total costs, 3 months prior 0.08 (0.03)** 0.09 (0.02)*** Axillary node dissection 0.20 (0.09)** 0.16 (0.09)* Surgical types Single BCS 0.45 (0.12)*** 0.02 (0.10) Multiple BCS 0.67 (0.12)*** 0.17 (0.11) BCS followed by mastectomy 0.29 (0.13)** 0.34 (0.09)*** Adjuvant care types Radiation only 0.66 (0.10)*** Chemotherapy only 0.72 (0.15)*** Radiation + chemotherapy 1.17 (0.09)*** Smearing factors Mastectomy alone BCS followed by mastectomy No adjuvant care N/A 1.11 Radiation only N/A 1.06 Chemotherapy only N/A 1.15 Radiation + chemotherapy N/A 1.03 Adjusted R * P<0.10, ** P<0.05, *** P<0.01 Omitted categories: 1 or fewer comorbidities, in situ/local stage, mastectomy, no adjuvant care, and no axillary node dissection. (parentheses White s standard errors) Eur J Health Econom

5 Original Papers Table 4 Relative magnitude of costs of surgical and adjuvant care interventions for breast cancer Surgical interventions Total costs Mastectomy only Reference Single BCS 1.38 Multiple BCS 1.64 BCS followed by mastectomy 1.21 Adjuvant care interventions No adjuvant care Reference Radiation only 1.83 Chemotherapy only 2.12 Radiation and chemotherapy 2.98 val (CI) $17,558 $25,694]. The costs for patients treated with single BCS procedure were about $5,000 higher ($26,373 total) and the most costly treatment route was multiple BCS procedures at a cost of $30,884 (95% CI $28,497 $34,900).A BCS followed by mastectomy was close to the cost of mastectomy alone, $22,350 (95% CI $19,600 $26,687). Table 6 shows cost estimates by adjuvant care regimens (including prior surgical interventions). The adjusted cost for patients receiving radiation without chemotherapy was $26,797. This category refers almost exclusively to patients undergoing a BCS as their first surgery. Three patients who initially had a mastectomy received subsequent radiation. The mean total adjusted costs for patients who received chemotherapy without radiation (in addition to surgery) was $30,362 and for patients who received both radiation and chemotherapy the mean cost was $39,305 in the year following breast cancer diagnosis. Our last research question was to determine whether patients medical expenditures returned to their prior level once cancer was treated. This question challenges the validity of treatment phases and explores the possibility that the presence of cancer affects other health problems and conditions or that cancer treatment has some long-term negative side effects that require medical attention. Figure 1 shows that medical care expenditures spike in the first month after diagnosis during the surgical period. Certain interventions such as surgery and radiation incur large costs within the first 3 months,but returned to prior expenditure levels after the fifth month and remain constant over the course of the year. Likewise, the cost for other interventions occurred within the first 5 months, but returned to prior levels in the fifth month. One exception to this pattern was chemotherapy interventions that may be administered throughout the year. A mastectomy did not appear to increase costs over the course of the following year. In contrast, adjuvant combinations of radiation and chemotherapy continued to affect costs over the course of the year. An interesting question for future research is to determine how patient outcomes (both survival and morbidity) are affected by the initial treatment choice particularly those that frequently lead to multiple surgeries. Conclusions We showed that if the surgical choice was mastectomy, medical care use tends to return to precancer diagnosis levels within a few months, whereas BCS leads to increased costs over the course of the year. Studies examining the cost of breast cancer care to the end of life have shown that costs increase in the final 6 months of life [10, 14, 18]. Since no one died during our study period, the effect of death or late stage was not observed. Our analysis also revealed that adjuvant care was strongly associated with BCS in the prediction of cost. In addition, adjuvant care was strongly associated with disease stage in cost prediction. In models where adjuvant care was excluded (column 1 of Table 3), stage was an independent predictor of cost, but was no longer statistically significant when adjuvant care was added to the model; however, this does not imply that stage no longer has a role in the prediction of costs. For example, all patients receiving chemotherapy naturally have higher costs relative to patients who do not receive chemotherapy. Many but not all of these chemotherapy patients will have late stage disease; therefore chemotherapy appears to drive the cost rather than stage. Instead, both have important roles in the prediction of the total cost of care. Other correlates of cost included physical functioning, comorbidity, costs prior to diagnosis, and axillary node dissection. In our sample, most women had multiple surgeries within a short period of time if their first surgery was breast conserving. Previous studies partition- Table 5 Prediction of mean total adjusted costs by surgical type during the year following breast cancer diagnosis Surgical intervention eˆβx Smearing factor Mean cost a 95% CI Mastectomy only $17, $21,274 $17,558 $25,694 Single BCS $24, $26,373 $23,592 $29,985 Multiple BCS $29, $30,884 $28,497 $34,900 BCS followed by mastectomy $20, $22,350 $19,600 $26,687 a Numbers may not appear exact due to rounding Table 6 Prediction of mean total adjusted costs by adjuvant care regimen during the year following breast cancer diagnosis Adjuvant interventions eˆβx Smearing factor Mean cost a 95% CI No adjuvant care $14, $16,226 $14,147 $19,752 Radiation only $25, $26,797 $25,075 $31,916 Chemotherapy only $26, $30,362 $23,478 $39,772 Radiation + chemotherapy $38, $39,305 $32,455 $44,388 a Numbers may not appear exact due to rounding 100 Eur J Health Econom

6 Fig. 1 Average cost per month by surgical option ing costs into disease phases miss this very important pattern. Some research leads us to believe that surgery is a onetime event where the decision is either mastectomy or BCS; however, that apparently is not the case. This is a serious consideration for older women who could be faced with substantial morbidity from multiple surgical events. It is also a costly method of practice for just over 50% of our sample. Prior to making a decision about which treatment strategy is best for the treatment of breast cancer, patient outcomes, quality of life, and preferences should be considered [18]. Examining this decision strictly from a cost perspective, mastectomy (without prior BCS or subsequent adjuvant care) is the least expensive option. Two limitations should be discussed. First, we estimated costs over the course of the year following breast cancer diagnosis instead of estimating lifetime costs. The 1 year window is appealing because most of the intensive treatment (as shown in Fig. 1) occurs within the first 5 months following diagnosis, then medical care use may return to what levels prior to cancer diagnosis. Second, our findings from a sample of an older, mostly white population of women from Michigan may not be reflected in the general population. While this may be the case, we would argue that the course of care for cancer follows standard treatment protocols. Once women are diagnosed with breast cancer, their treatment options are based on disease stage and patient preferences. In a large national sample of breast cancer cases similar patterns were found [18]. In conclusion, our analysis revealed both important correlates of cost and unexpected practice patterns. Treatment choices involving BCS are clearly more expensive than mastectomy options because of the high probability of subsequent surgeries and the need for adjuvant care. For our population of women over the age of 65 years,many had multiple surgeries following diagnosis, leading to substantial costs and unknown morbidity. Future studies are required to understand if the benefits (e.g., expected utility gained from organ preservation) are balanced against the investment made in resources and morbidity losses (that may or may not be temporary). Clinical decisions are often confronted with how to provide effective care within a finite set of resources. This contribution attempts to draw out more carefully the relationship between treatment protocol and costs for breast cancer patients. Acknowledgements. This research was supported by a grant entitled Family Home Care for Cancer A Community-Based Model from: the National Institute of Nursing Research and National Cancer Institute (grant no. NR ), in collaboration with the Walther Cancer Institute, Indianapolis, Ind.; and a project entitled Cancer Care Intervention to Improve Functions and Psychosocial Outcomes in Newly Diagnosed Cancer Patients and their Families ; and a project entitled Cancer Prevention, Outreach, and Cancer Control in Community Based Programs from the Michigan Department of Community Health. References 1. Anonymous (1996) Aging and nealth in america survey Ann Arbor: University of Michigan, Survey Research Center, Institute for Social Research 2. American Joint Committee on Cancer (1997) AJCC cancer staging manual, 5th edn. Philadelphia: Lippencott,Williams, and Wilkins 3. Andersen C, Andersen K, Kragu-Sorensen P (2000) Cost function estimation: the choice of a model to apply to dementia. Health Econ 9: Baker M, Kessler L, Urban N, Smucker R (1991) Estimating the treatment costs of breast and lung cancer. 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