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Keywords:

  • colorectal cancer;
  • treatment;
  • disparity;
  • race/ethnicity;
  • time trend

Abstract

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

BACKGROUND.

Racial differences have been demonstrated in patients who receive treatment for colorectal cancer. However, little is known about whether these disparities have changed over time. The objective of this study was to determine whether racial disparities in receiving standard therapy have declined between 1991 and 2002.

METHODS.

The study population consisted of 59,803 Caucasians and African Americans aged ≥65 years who were diagnosed with colorectal cancer (American Joint Committee on Cancer stages I, II, and III) between 1991 and 2002 and were identified from the Surveillance, Epidemiology, and End Results Program/Medicare-linked database. Standard therapy for colorectal cancer was defined based on the Physician Data Query guidelines from the National Cancer Institute. The crude and age- and sex-adjusted percentages and the odds ratios (ORs) of receiving standard therapy were reported.

RESULTS.

From 1991 to 2002, the percentage of patients who did not receive standard therapy for colorectal cancer decreased for both Caucasians (from 24.5% to 22.4%) and African Americans (from 30.4% to 26.4%). Overall, African Americans were 16% less likely to receive standard therapy for colorectal cancer (OR, 0.84; 95% confidence interval [CI], 0.78-0.90) than Caucasians, but the difference was not significant after the analysis was adjusted for other factors (OR, 0.96; 95% CI, 0.88-1.05). The gap for not receiving standard therapy was relatively stable, peaked in 1997 (7.2%), and decreased from 1999 to 2002 (from 7.1% to 4%).

CONCLUSIONS.

The percentage of patients receiving standard therapy for colorectal cancer increased over time, but disparities remained and decreased in recent years. Future studies should include other ethnic groups and should incorporate provider and system factors that may contribute to treatment disparities. Cancer 2008. © 2008 American Cancer Society.

In the United States, African Americans experience higher rates of cancer morbidity and mortality than Caucasians.1 This disparity is evident for colorectal cancer, which is one of the most common malignancies in both men and women with an estimated 148,810 new cases in 2008.2 African Americans bear a disproportionate burden from colorectal cancer. For example, for the years 1996 through 2003, the overall age-adjusted cancer incidence and mortality were higher among African Americans than among all other racial/ethnic groups.2 Furthermore, for the same period, African Americans had 5-year cancer survival rates of 55% and 58% for cancers of the colon and rectum, respectively, compared with 66% for both cancers among whites.2 These disparities in outcomes should not exist, because colorectal cancer is amenable to treatment and often is curable when diagnosed at the local stage.3

There have been advances in colorectal cancer treatment over the past 2 decades. Surgical resection remains the primary treatment for stage I, II, and III colorectal cancer.3 In 1990, the National Institutes of Health (NIH) Consensus Conference recommended giving adjuvant chemotherapy, which improved survival for patients with stage III colon cancer in clinical trials, to all patients with stage III colon cancer who were not enrolled in clinical trials.4 That conference also suggested the use of combined adjuvant chemotherapy and high-dose external-beam radiotherapy for treating patients with stage II or III rectal cancer.4 It was noted that, although radiation therapy did not affect disease-specific or overall survival, it did decrease local recurrence, which is associated with significant morbidity.4 In addition, the National Cancer Institute began providing up-to-date treatment guidelines based on evidence from research.3, 5 Despite the evidence supporting standard therapy, many studies have documented a disparity in colorectal cancer treatment between African Americans and Caucasians.6–10 For example, several population-based studies determined that African Americans with stage III colon cancer were less likely than Caucasians to undergo surgical resection and receive adjuvant chemotherapy.6–10

Little is known about whether the racial/ethnic gap in standard therapy is narrowing over time. Two studies have explored colon and/or rectal cancer treatment over time.10, 11 Jessup et al used data from the National Cancer Data Base and observed that adjuvant chemotherapy use for stage III colon cancer was significantly less common for blacks from 1991 to 1992 and from 1995 to 1996, but it was not different from that for other ethnic groups from 2001 to 2002.11 However, the authors did not adjust for patient, tumor, provider, or health system characteristics. Conversely, using data from the Surveillance, Epidemiology, and End Results (SEER) Program/Medicare-linked database (SEER/Medicare), Gross et al observed that there was no decrease in the magnitude of racial disparities between blacks and whites from 1992 to 2002 in the use of adjuvant chemotherapy for stage III colon cancer or in the use of adjuvant chemotherapy and (neo)adjuvant radiation for stage II and III rectal cancer.10 Those investigators adjusted their analyses for patient and tumor characteristics. Both studies compared the receipt of treatment during 2- or 3-year intervals, and the latter study compared adjuvant therapy only in patients who were treated from 2000 to 2002 with patients who were treated from 1992 to 1994.10

It remains unclear the extent to which standard therapy for stage I, II, and III colorectal cancer has been received by racial/ethnic groups over time. Therefore, the objective of the current study was to determine whether racial/ethnic disparities in the receipt of standard therapy for colorectal cancer declined or narrowed between 1991 and 2002 in the United States. This period was optimal for the current investigation because we were able to assess whether there were improvements after the NIH Consensus Conference determined the standard therapy for stage III colon cancer and stage II and III rectal cancers in 1991. By using a large, population-based cohort of patients with colorectal cancer from the SEER/Medicare data, we hypothesized that the racial/ethnic gap between African Americans and Caucasians receiving standard treatment would decline between 1991 and 2002 for patients with colorectal cancer but that the gap would remain significant even after controlling for differences in patient demographics, socioeconomic status, tumor characteristics, and year of diagnosis. We believe that examining these trends will lead to a better understanding of the factors that contribute to this disparity and ultimately could lead to policy changes that may reduce the gap in standard therapy between Caucasians and African Americans.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

Data Sources

The SEER/Medicare-linked data files12–14 were used to provide information about incident cancer diagnoses and cancer-directed therapy as well as Medicare eligibility, enrollment, and claims for patients aged ≥65 years who were diagnosed with colorectal cancer. The SEER Program collects demographics, tumor characteristics, information on the first course of treatment, and cause of death information for individuals with cancer.13 By the Year 2000, there were 17 SEER registries that covered 26.2% of the United States population and included the following areas: San Francisco-Oakland; Detroit; Atlanta; Rural Georgia; Seattle-Puget Sound; Los Angeles County; the San Jose-Monterey area; Greater California; Alaska Natives; and the states of Connecticut, Iowa, New Mexico, Utah, Hawaii, Kentucky, Louisiana, and New Jersey.13 In the current study, we did not include the Alaska Native Registry because of the very small number of cases reported. We combined Atlanta and Rural Georgia.

Medicare is a federally funded program that provides health insurance primarily for individuals aged ≥65 years. To ensure the completeness of Medicare claims, patients who did not have full coverage that included both Medicare Parts A and B or who were members of a Health Maintenance Organization during the year when their diagnosis was made were excluded from the study. Medicare eligibility could be identified for 94% of the individuals aged ≥65 years who appeared in the SEER records.14 The University of Texas Health Science Center at Houston Committee for Protection of Human Subjects approved the study protocol.

Study Population

The study population consisted of 59,803 men and women aged ≥65 years who were diagnosed with incident American Joint Committee on Cancer (AJCC) stage I, II, or III colorectal cancer between January 1, 1991 and December 31, 2002. Patients with stage IV disease were excluded because of heterogeneity in the treatment of patients with distant metastatic disease. Individuals with multiple primary tumors were also excluded. Of the 59,803 individuals, 92.3% were Caucasian, and 7.7% were African American.

Study Variables

Standard therapy

The primary outcome variable in this study was the receipt of standard therapy, which was based on the Physician Data Query guidelines from the National Cancer Institute.3, 4 These treatment guidelines are AJCC stage-specific. Receipt of therapy was assessed by using the minimum therapy required for each stage. Surgical resection was defined as standard therapy for patients with stage I colon cancer. Standard therapy for stage II disease also was defined as surgery alone, because controversy remains regarding whether adjuvant chemotherapy should be used after surgery in patients with stage II colon cancer. For patients with stage III colon cancer, standard therapy was defined as surgical resection followed by adjuvant chemotherapy.3 For patients who had a diagnosis of rectal cancer, standard therapy was defined as surgical resection for stage I disease, whereas surgical resection followed by chemotherapy and radiation was considered standard therapy for patients with stage II and III disease.5

Surgical resection for colon cancer was defined as partial, subtotal, or total colectomy (SEER codes 30, 40, 50, 60, or 70)15 using the SEER registry, which collects information on the first course of treatment received within 4 to 6 months of diagnosis. For cancers of the rectum, surgical resection included low anterior resection (SEER codes 30 and 40), abdominoperineal resection (SEER codes 50 and 60), and pelvic exenteration (SEER code 70). Medicare claims also were used to identify surgical resection received within 6 months of diagnosis (International Classification of Diseases, 9th Revision, Clinical Modification procedure codes16 45.71-45.76, 45.79-45.89, 48.41, and 48.49-48.69 or Common Procedure Terminology codes17 44,140-44,160 or 45,110-45,121) for colorectal cancer. Radiation therapy was identified from both SEER and Medicare claims by using previously reported methods.18 Similarly, detailed methods for the identification of chemotherapy using Medicare claims have been described previously.19–22 Chemotherapy consisted primarily (98%) of fluorouracil-based regimens.

Patient and tumor characteristics

The following patient and tumor characteristics were assessed in the study: year of diagnosis, age (categorized as ages 65-69 years, 70-74 years, 75-79 years, 80-84 years, or ≥85 years), marital status (married, unmarried, or unknown), sex (man or woman), socioeconomic status (quartiles of poverty, with the first quartile denoting high socioeconomic status), tumor stage (AJCC stage I, II or III), tumor size (<1.0 cm, 1.0-1.9 cm, 2.0-2.9 cm, 3.0-3.9 cm, ≥4.0 cm, or missing), tumor grade (well differentiated, moderately differentiated, poorly differentiated, or unknown), number of positive lymph nodes (0, 1, 2-3, 4-5, 6-9, 10-51, or missing), SEER geographic area (SEER regions), and urban/rural residence(big metropolitan, metropolitan, urban, less urban, or rural). Information on comorbidities was ascertained from Medicare claims by identifying 18 diagnoses or related procedures that were recorded between 1 year before and 1 month after the diagnosis of colorectal cancer. Details on creating a weighted comorbidity score have been reported previously.12, 23 The comorbidity score was coded as 0, 1, 2, 3, or ≥4. In addition, several common comorbidities were identified and classified as present or absent, including myocardial infarction, congestive heart failure, dementia, diabetes, and liver disease.

Data Analysis

Patient and tumor characteristics were stratified by racial/ethnic group and were summarized by using descriptive statistics. Differences were assessed by using the chi-square statistic. P values ≤.05 were considered statistically significant. The receipt of standard therapy was evaluated by calculating the percentage of patients that received standard therapy for each year. Both crude and age-adjusted rates of receiving standard care by year and the disparity between African Americans and Caucasians were estimated. Furthermore, linear regression was used to test for linear trend in the differences in the rates of receiving standard care from 1991 to 2002. Finally, multivariate logistic regression was used to assess the effect of time and race/ethnicity on the odds of receiving standard therapy. Potential effect-measure modifiers were identified in the literature and were assessed by using the likelihood ratio test for homogeneity. Data-based confounding also was assessed. Five multivariate models are presented. All data were analyzed using the statistical software package Intercooled Stata version 9.0 (Stata Corporation, College Station, Tex).

RESULTS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

The distributions of patient and tumor characteristics for Caucasians and African Americans who were diagnosed with stage I through III colorectal cancer during 1991 through 2002 are presented in Table 1. Many patient characteristics varied by race. First, Caucasians were slightly older at diagnosis, with a median age of 77 years compared with 75 years for African Americans. For example, 22.5% of African Americans were diagnosed at ages 65 to 69 years compared with only 17.4% of Caucasians. Second, although women made up the majority of patients for both races, the proportion of women was significantly greater for African Americans (62.1%) than for Caucasians (56.0%). Third, 50.1% of Caucasians were married at the time of diagnosis compared with 34% of African Americans. Fourth, although there were significant differences in year of diagnosis, for the most part, the percentages by year for each racial group were similar. Finally, significantly greater percentages of African Americans (70.7%) were in the lowest or poorest socioeconomic quartile compared with Caucasians (18.8%).

Table 1. Patient and Tumor Characteristics of Caucasians and African Americans Diagnosed With Stages I Through III Colorectal Cancer, 1991-2002
CharacteristicCaucasiansAfrican AmericansP
No.%No.%
  • SES indicates socioeconomic status; AJCC, American Joint Committee on Cancer; SEER, Surveillance, Epidemiology, and End Results.

  • *

    SES was based on the percentage of census tract residents below poverty, with the first quartile denoting high SES.

Age, y    <.001
 65-69961817.4103322.5 
 70-7412,09921.9111624.3 
 75-7912,88923.4108223.5 
 80-8410,75919.576816.7 
 ≥85983917.860013.1 
Sex    <.001
 Men24,32044.1174237.9 
 Women30,88456285762.1 
Marital status    <.001
 Married27,62850.1156534 
 Unmarried25,54846.3283661.7 
 Unknown20283.71984.3 
SES (high to low)*    <.001
 First quartile15,40127.92655.8 
 Second quartile14,68726.63517.6 
 Third quartile14,15525.670915.4 
 Fourth quartile10,37318.8324970.7 
 Unknown5881.1250.5 
Tumor stage (AJCC)    .071
 I18,33033.2148632.3 
 II21,19638.4173437.7 
 III15,67828.4137930 
Tumor size, cm    <.001
 <114582.61332.9 
 1-<224044.41573.4 
 2-<3558310.13708.1 
 3-<4852915.571615.6 
 >426,59548.2223948.7 
 Missing10,63519.398421.4 
Tumor grade    <.001
 Well differentiated55441046410.1 
 Moderately differentiated34,81063.1298865 
 Poorly differentiated998718.160713.2 
 Unknown48638.854011.7 
Comorbidity score    <.001
 028,90452.4207445.1 
 114,81626.8124427.1 
 2631711.458812.8 
 326614.82936.4 
 ≥425064.64008.7 
No. of positive lymph nodes    <.001
 030,95656.1239152 
 149368.947710.4 
 2-348358.84219.2 
 4-521313.92054.5 
 6-915782.91463.2 
 10-5112962.41032.2 
 Missing947217.285618.6 
SEER registry    <.001
 San Francisco-Oakland30965.63477.6 
 Connecticut768513.92735.9 
 Detroit671612.2139930.4 
 Hawaii3430.660.1 
 Iowa834215.1681.5 
 New Mexico17753.2310.7 
 Seattle-Puget Sound45928.3902 
 Utah20953.890.2 
 Atlanta/Rural Georgia21773.970615.4 
 San Jose-Monterey19083.5340.7 
 Los Angeles50379.160513.2 
 Greater California35276.41092 
 Kentucky22604.11162.5 
 Louisiana14542.64229.2 
 New Jersey41977.63848.4 
Urban/rural residence    <.001
 Big metropolitan29,61453.6372681 
 Metropolitan15,72328.560613.2 
 Urban37356.8851.9 
 Less urban498991643.6 
 Rural11432.1180.4 
Year of diagnosis    .004
 199134486.32495.4 
 199240387.33156.9 
 199338186.92645.7 
 199437006.73096.7 
 199536796.72916.3 
 199636546.62806.1 
 199734866.33106.8 
 199836026.53166.9 
 199934506.32856.2 
 2000732513.363013.7 
 2001744213.567114.6 
 2002756213.769014.8 
Total55,2041004599100 

When comparing tumor characteristics, there were some noteworthy variations between the 2 populations. Although the differences in disease stage at diagnosis and tumor size between these groups were relatively small, African Americans had a greater proportion of patients with unknown tumor grade (11.7%) compared with Caucasians (8.8%). African Americans also had more positive lymph nodes. A greater percentage of African Americans (8.7%) had comorbidity scores ≥4 compared with Caucasians (4.6%). Finally, there was significant geographic variation among the 2 groups. A greater percentage of African Americans lived in big metropolitan areas (81%) at the time of diagnosis compared with Caucasians (53.6%). More African Americans resided in Detroit, Atlanta/Rural Georgia, Louisiana, San Francisco-Oakland, and New Jersey at the time of diagnosis.

Table 2 compares the standard therapy and various component modalities of treatment received by Caucasians and African Americans who were diagnosed with colorectal cancer. Overall, 73.7% of African Americans versus 77% of Caucasians received standard therapy. These differences remained apparent when individual modalities were considered. Specifically, more Caucasians than African Americans received surgery, radiation, and chemotherapy. Furthermore, a slightly higher percentage of African Americans refused surgery (0.9%) than Caucasians (0.4%). More African Americans (2.4%) did not receive a recommendation from their physician for surgery compared with Caucasians (1.4%). Approximately 0.8% of African Americans and 0.6% of Caucasians were not recommended for surgery because of contraindications.

Table 2. Comparison of Treatment Received by Caucasians and African Americans Diagnosed With Colorectal Cancer (American Joint Committee on Cancer Stages I-III), 1991-2002
CharacteristicCaucasianAfrican AmericansP
No.%No.%
  1. SEER indicates Surveillance, Epidemiology, and End Results.

Standard therapy    <.001
 Yes42,49377338773.7 
 No12,71123121226.4 
Surgical resection    <.001
 Yes52,52895.2430993.7 
 No26764.92906.3 
Surgery    <.001
 Cancer directed53,13696.3433194.2 
 Not recommended7621.41102.4 
 Not recommended-contraindicated3070.6370.8 
 Refused2050.4410.9 
 Recommended, unknown whether done970.2120.3 
 Unknown6971.3581.5 
Radiation from SEER or Medicare    .043
 Yes93951772915.9 
 No45,80983387084.2 
Radiation from SEER    <.001
 None48,90988.6417490.8 
 Radiation494793397.4 
 Refused2510.5200.4 
 Recommended, unknown administration2900.5280.6 
 Unknown8071.5380.8 
Chemotherapy    <.001
 Yes16,19229.3118025.7 
 No39,01270.7341974.3 
Total55,2041004599100 

Table 3 presents the crude and age- and sex-adjusted percentages of men and women who received standard therapy for colorectal cancer stratified by race/ethnicity. From 1991 to 2002, the percentage of patients who did not receive standard therapy for colorectal cancer decreased for both Caucasians (from 24.5% to 22.4%) and African Americans (from 30.4% to 26.4%). However, the disparity in not receiving standard therapy for colorectal cancer between African-American patients and Caucasian patients was relatively stable between 1991 and 1996 (≈5%), but there was a drop in 1993. The gap peaked in 1997 (7.2%) and decreased from 1999 to 2002 (from 7.1% to 4%). These results are illustrated in Figure 1, which displays the trends over time for not receiving standard therapy for colorectal cancer stratified by race. The overall disparity trend was not significant (P = .96). There was a slight descending trend for the disparity among groups from 1999 to 2002; however, this trend was not statistically significant (P = .17). To determine whether the addition of Greater California, Kentucky, Louisiana, and New Jersey to the SEER registry in 2000 influenced results, we also analyzed the data excluding these states. Overall, the trends were very similar. However, from 1999 to 2001, the decrease (2 percentage points) was smaller for the analysis that excluded the expansion states compared with the analysis that included the expansion states (4 percentage points).

thumbnail image

Figure 1. Percentage of patients who did not receive standard therapy for colorectal cancer over time stratified by race/ethnicity.

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Table 3. Crude and Age/Sex-Adjusted Percentage of Men and Women Who Did Not Receive Standard Therapy for Colorectal Cancer by Race/Ethnicity
Year of DiagnosisPatients Who Did Not Receive Standard Therapy for Colorectal CancerDisparity Between African-Americans and Caucasians
Caucasians (n=55,204)African Americans (n=2599)  
No.Crude %Age/Sex-Adjusted %No.Crude %Age/Sex-Adjusted %Crude %Age/Sex-Adjusted %
1991344824.324.524929.330.45.15.9
1992403824.224.531528.629.64.45.1
1993381823.423.626422.423.9−1.10.3
1994370023.523.530827.928.84.55.3
1995367924.424.729127.229.72.85
1996365422.422.32802526.42.64.1
1997348622.522.231027.729.45.37.2
1998360222.922.631624.726.61.84
1999345021.220.828527.727.96.67.1
2000732522.622.363025.927.23.34.9
2001744223.122.867126.125.933.1
2002756222.622.468025.626.434

Finally, Table 4 summarizes the multivariate analysis on the odds of receiving standard therapy. Overall, African Americans were 16% less likely to receive standard therapy for colorectal cancer (OR, 0.84; 95% CI, 0.78-0.90) during this period. However, this relation was attenuated and was no longer statistically significant after adjusting for year of diagnosis, age, marital status, sex, socioeconomic status, tumor stage, tumor size, tumor grade, number of positive lymph nodes, comorbidity score, SEER registry, and urban/rural residence (adjusted OR, 0.96; 95% CI, 0.88-1.05). Table 4 also shows the effect of age, sex, socioeconomic status, and year of diagnosis on the receipt of therapy for colorectal cancer. Women were significantly more likely to receive this therapy, whereas older patients and those with poor socioeconomic status were less likely to receive standard therapy. Patients who were diagnosed in more recent years were more likely to receive therapy as recommended. In additional analyses of the relation between receipt of standard therapy and race by year of diagnosis, the results were similar to those illustrated in Table 3. For example, African Americans were 13% less likely to receive standard therapy than Caucasians in 1991 (OR, 0.77; 95% CI, 0.57-1.03), but this ratio decreased slightly to 11% by 2002 (OR, 0.89; 95% CI, 0.73-1.08). In addition, the multivariate analysis was compared with an additional analysis that excluded the states that were added to the SEER registry in 2000, and no significant differences were observed.

Table 4. Multivariate Analyses on Receiving Standard Therapy for Colorectal Cancer (American Joint Committee on Cancer Stages I-III)
VariableOR (95% CI) of Receiving Standard Therapy
Model 1*Model 2Model 3Model 4§Model 5||Model 6
  • OR indicates odds ratio; CI, confidence interval;

  • *

    Model 1 represents the crude relation.

  • Model 2 was adjusted for the year of diagnosis.

  • Model 3 was adjusted for age (5 categories), marital status, sex, and SES in addition to the factors in Model 2.

  • §

    Model 4 was adjusted for tumor stage, size, grade, number of positive lymph nodes, comorbidities, and the factors in Model 3.

  • ||

    Model 5 was adjusted for Surveillance, Epidemiology and End Results registry and the factors in Model 4.

  • Model 6 was adjusted for urban/rural residence and the factors in Model 5.

  • #

    Statistically significant OR.

  • **

    SES was based on the percentage of census tract residents below poverty, with first quartile denoting high SES.

Race/ethnicity      
 Caucasian1.001.001.001.001.001.00
 African-American0.84 (0.78-0.90)#0.84 (0.78-0.89)#0.87 (0.81-0.94)#0.94 (0.87-1.02)0.95 (0.87-1.03)0.96 (0.88-1.05)
Age, y      
 65-691.001.001.001.00
 70-740.89 (0.83-0.95)#0.87 (0.80-0.93)#0.87 (0.80-0.93)#0.87 (0.80-0.93)#
 75-790.74 (0.69-0.79)#0.66 (0.61-0.71)#0.66 (0.62-0.71)#0.66 (0.61-0.71)#
 80-840.55 (0.51-0.58)#0.46 (0.42-0.49)#0.46 (0.42-0.49)#0.46 (0.42-0.49)#
 ≥850.41 (0.38-0.44)#0.31 (0.29-0.34)#0.31 (0.29-0.34)#0.31 (0.29-0.34)#
Sex      
 Men1.001.001.001.00
 Women1.20 (1.15-1.25)#1.18 (1.13-1.24)#1.18 (1.13-1.24)#1.18 (1.13-1.24)#
SES (high to low)**      
 First quartile1.001.001.001.00
 Second quartile0.96 (0.91-1.01)0.95 (0.89-1.01)0.93 (0.88-0.99)#0.92 (0.87-0.98)#
 Third quartile0.92 (0.87-0.97)#0.92 (0.86-0.97)#0.89 (0.84-0.95)#0.88 (0.82-0.94)#
 Fourth quartile0.83 (0.79-0.88)#0.83 (0.78-0.88)#0.82 (0.76-0.88)#0.80 (0.74-0.86)#
 Unknown0.78 (0.65-0.94)#0.77 (0.62-0.95)#0.77 (0.62-0.96)#0.76 (0.61-0.94)#
Year of diagnosis      
 19911.001.001.001.001.00
 19921.01 (0.91-1.12)1.01 (0.91-1.12)1.01 (0.90-1.14)1.03 (0.91-1.15)1.03 (0.91-1.15)
 19931.07 (0.96-1.19)1.07 (0.97-1.19)1.10 (0.97-1.24)1.11 (0.98-1.25)1.11 (0.98-1.25)
 19941.05 (0.94-1.16)1.06 (0.95-1.18)1.09 (0.97-1.23)1.10 (0.98-1.24)1.10 (0.98-1.24)
 19951.00 (0.91-1.11)1.00 (0.90-1.11)1.08 (0.96-1.21)1.09 (0.96-1.22)1.08 (0.96-1.22)
 19961.12 (1.01-1.24)#1.15 (1.03-1.28)#1.17 (1.04-1.32)#1.18 (1.05-1.33)#1.18 (1.04-1.33)#
 19971.10 (0.99-1.23)1.14 (1.02-1.27)#1.17 (1.04-1.32)#1.18 (1.05-1.34)#1.18 (1.05-1.33)#
 19981.10 (0.99-1.22)1.12 (1.01-1.25)#1.18 (1.04-1.33)#1.18 (1.05-1.34)#1.18 (1.05-1.33)#
 19991.18 (1.06-1.32)#1.23 (1.10-1.37)#1.20 (1.06-1.35)#1.20 (1.06-1.36)#1.20 (1.06-1.36)#
 20001.11 (1.01-1.21)#1.17 (1.07-1.29)#1.19 (1.07-1.33)#1.23 (1.10-1.38)#1.23 (1.10-1.37)#
 20011.08 (0.98-1.18)1.12 (1.02-1.23)#1.10 (0.99-1.22)1.14 (1.02-1.27)#1.14 (1.02-1.27)#
 20021.11 (1.01-1.21)#1.14 (1.04-1.25)#1.15 (1.03-1.27)#1.19 (1.06-1.33)#1.18 (1.06-1.32)#

DISCUSSION

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

In this study, we compared racial differences and trends in cancer treatment between African Americans and Caucasians with colorectal cancer. We observed that there has been progress in ameliorating the treatment gap between these 2 groups. Specifically, the disparities in receiving standard therapy for colorectal cancer between African Americans and Caucasians were relatively stable from 1991 to 1996, peaked in 1997, and then decreased from 1999 to 2002.

Although numerous studies have documented a disparity in colorectal cancer treatment between African Americans and Caucasians,1, 6–11, 24–35 few studies have addressed the changes over time.19, 23 Jessup and colleagues observed that the use of adjuvant chemotherapy for treating stage III colon cancer was significantly less common among blacks from 1991 to 1992 and from 1995 to 1996, but its use did not differ from that among other ethnic groups from 2001 to 2002.11 However, Gross and colleagues observed that there was no decrease in the magnitude of these racial disparities between 1992 and 2002.10 The discrepancies between those studies and ours may be because of differences in defining standard therapy and in measuring the receipt of therapy over time. First, these other authors measured the racial disparities and changes over time primarily based on the receipt of adjuvant chemotherapy or radiation therapy, whereas our study was based mainly on the receipt of stage-specific, standard therapy as recommended by clinical guidelines.5 Therefore, depending on the specific disease (colon or rectal cancer) and stage, surgical resection that was not accompanied by adjuvant chemotherapy and/or radiation was considered suboptimal. Second, they compared the percentage of patients who received cancer therapy during 1992 through 1994 versus 2000 through 2002. In contrast, we measured the racial gap in the receipt of standard therapy by the year of diagnosis from 1991 to 2002, because it is critical to establish the changes closely by year, and there are sufficient numbers of patients each year to enable us to do so. It is evident from Table 4 and Figure 1 that treatment trends are likely to be overlooked when combining many years together.

Disparities in healthcare are common across various fields of medicine, as reported by the Institute of Medicine.1 Over the past decade, many efforts have been made to reduce the disparities in healthcare. There are contradictory reports on whether efforts to reduce or eliminate disparities in healthcare, which is 1 of the objectives set forth by the Healthy People 2010 initiative, have been successful. Although we have a long way to go to achieve this goal and, in many medical areas where there are still substantial racial/ethnic disparities, the decreasing percentage of those who do not receive standard therapy in both groups and the narrowing gap in the standard treatment of colorectal cancer between African Americans and Caucasians from 1999 to 2002, as documented in our study, certainly are encouraging. Moreover, a significant majority of patients with colorectal cancer received the standard of care as recommended, and the racial disparities in receiving this therapy were relatively small and were not statistically significant. If this trend continues and these findings can be replicated in other populations, then it seems promising that the 2010 goal can be achieved at least for patients with colorectal cancer.

Our study had several strengths. First, we included a large cohort of patients that represented population-based cases from the 16 SEER areas (Atlanta combined with rural Georgia), which account for nearly 26% of the United States population. These findings may have great generalizability to populations in other areas. Second, data pertaining to surgical resection and radiation therapy from SEER combined with Medicare claims represented accurate and complete sources,18, 36 and chemotherapy can be identified uniquely and reliably from Medicare claims. Consequently, standard therapy for colorectal cancer can be established reliably according to clinical guidelines. In addition, our cohort was covered by the Medicare insurance program, and their medical care claims would be filed in this program regardless of where they received care across the country. Furthermore, the clinical guidelines for colorectal cancer treatment have been relatively stable without major modifications over the past 12 years,3, 4 so the findings were less likely to be affected by clinical and other factors.

There also were some limitations in this study. First, there was limited information available on patient-level factors, such as patient preferences and other issues that may have played a role in the selection of various treatment options. Despite this shortcoming, we were able to compare the rate of treatment refusals for surgery and radiation therapy by race. Although African Americans had a higher percentage of refusals for surgery (0.89% vs 0.37%), these differences were too small to explain the overall racial differences in receiving standard care. Second, hospital- and physician-level characteristics were not included in this analysis. Factors like area variation in physician practice style and healthcare delivery may explain some of the racial differences. Third, we used the percentage of individuals living under the poverty line at the level of census tract as a measure of socioeconomic status, which may not be an ideal indicator for the elderly.37 Furthermore, other components of socioeconomic status, such as education, were not included in our analysis but may play an important role in receiving treatment. Finally, our study population included only Medicare beneficiaries aged ≥65 years who had full coverage of Parts A and B and without Health Maintenance Organization enrollment. Therefore, the current findings may not be generalizable to other populations and to patients aged <65 years.

In conclusion, the percentage of patients receiving standard therapy for colorectal cancer increased over time for both African Americans and Caucasians, but the gap remained and decreased in recent years from 1999 to 2002. Future studies should include other ethnic groups and should incorporate other factors that may contribute to treatment disparities, such as patient phenomenon in this and younger populations, so that disparities can be addressed through policy or other interventions.

Acknowledgements

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES

We acknowledge the efforts of the National Cancer Institute; the Centers for Medicare and Medicaid Services; the Institute of Mathematical Sciences; and the Surveillance, Epidemiology, and End Results tumor registries in the creation of this database. The interpretation and reporting of these data are the sole responsibilities of the authors.

REFERENCES

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgements
  7. REFERENCES
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