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Who Gets Adjuvant Treatment for Stage II and III Rectal Cancer? Insight From Surveillance, Epidemiology, and End Results–Medicare

From the Departments of Epidemiology and Biostatistics, Medicine, Surgery, and Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY.

Address reprint requests to Deborah Schrag, MD, Health Outcomes Research Group, Department of Epidemiology and Biostatistics Memorial-Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10021; email: schragd{at}mskcc.org

	ABSTRACT

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
PURPOSE: To examine the relationship between patient characteristics and the use of adjuvant pelvic radiation with and without chemotherapy among patients aged 65 years and older with stage II and III rectal cancer.

PATIENTS AND METHODS: A retrospective cohort study using the Surveillance, Epidemiology, and End Results–Medicare linked database identified 1,411 patients aged 65 and older with resected stage II and III rectal cancers diagnosed between 1992 and 1996. From claims submitted to Medicare, we measured the use of pelvic radiation therapy with or without chemotherapy and pre- or postoperatively.

RESULTS: Fifty-seven percent of patients received radiation, 42% received chemotherapy and radiation, and 7% had treatment delivered preoperatively. Age was the strongest determinant of treatment: 73% of patients aged 65 to 69, 66% aged 70 to 75, 52% aged 75 to 79, 39% aged 80 to 84, and 21% aged 85 to 89 received radiation. The age trend remained strong after adjusting for other factors that predict receipt of treatment and after exclusion of patients with any evident comorbidity (P < .001). Patients were more likely to receive radiation treatment if they had an abdominal perineal resection, stage III disease, or a T4 tumor.

CONCLUSION: Because pelvic recurrences are a substantial cause of morbidity, further efforts are needed to ensure that elderly patients have the opportunity to make informed decisions regarding adjuvant treatment.

	INTRODUCTION

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
RANDOMIZED, CONTROLLED clinical trials conducted in the 1980s evaluated the role of adjuvant radiation for patients with stage II and III rectal cancers and established that treatment substantially reduces the risk of local recurrence.^1-5 When administered with fluorouracil-based chemotherapy, adjuvant radiation improves survival, and thus combined-modality treatment has been recommended as standard-of-care since a 1990 National Institute of Health (NIH) Consensus statement and is recognized as an indicator of high-quality cancer care.⁶

In this study we sought to determine the extent to which adjuvant radiation treatment has been incorporated into routine practice among Medicare recipients with stage II and III rectal cancer and to identify patient characteristics that might be associated with a high probability of nontreatment. Because some clinicians may omit chemotherapy for the elderly, we measured the use rates of any adjuvant radiation treatment as well as those of combined-modality therapy. Furthermore, because there is increasing evidence that preoperative treatment may increase the ability to preserve fecal continence, we also looked at rates of preoperative treatment delivery.

In an analysis of adjuvant chemotherapy for Medicare beneficiaries with stage III colon cancer, we found that the overall use rate was 55%, but treatment rates varied dramatically with age at diagnosis. In addition, women, blacks, and patients with low median income were less likely to receive chemotherapy. We anticipated that similar trends would exist for adjuvant rectal cancer treatment.

	PATIENTS AND METHODS

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Data Sources
Linkage of the Surveillance, Epidemiology, and End Results (SEER) cancer registries with the Health Care Financing Administration’s Medicare database containing health care claims for its enrollees enabled us to identify a cohort of elderly patients with stage II and III rectal cancer. We used this resource to determine whether or not patients received adjuvant radiation and chemotherapy. The SEER registries ascertain all incident cancer cases diagnosed in five states and six metropolitan areas, representing approximately 14% of the United States population.⁷ SEER collects information on each incident cancer, including the primary site and histology classified according to the International Classification of Disease for Oncology,⁸ the tumor stage at diagnosis, as well as patient demographics.

The Medicare program provides health insurance for 97% of the United States population aged 65 and older. The Medicare Provider Analysis and Review files provide details of all hospitalizations for persons eligible for Medicare Part A. To receive payment, hospitals submit medical claims coding up to ten diagnoses and ten procedures using the International Classification of Diseases 9th Revision, Clinical Modifications (ICD-9-CM) classification. For the 96% of Medicare beneficiaries who opt for Part B coverage, claims for care delivered in hospital outpatient departments and physician’s offices are also recorded. Medicare documents date of death based on information provided by the Social Security Administration. The SEER and Medicare data have been linked to facilitate population-based studies of the medical and economic outcomes of cancer treatment. Ninety-four percent of patients in SEER aged 65 or older have been successfully linked to their Medicare records.⁹

Cohort Definition
All Medicare-enrolled patients aged 65 and older diagnosed with primary rectal cancer in a SEER area during the years 1992 to 1996 were potentially eligible for inclusion in our study. Rectal cancers were defined using the cancer site SEER code 20.9. Thus, tumors arising in the rectosigmoid were excluded. We restricted our cohort to patients with a histologic diagnosis consistent with adenocarcinoma (SEER histology codes 8140, 8210-11, 8220-21, 8260-63, 8470, 8480-81 and 8490). Diagnoses noted exclusively on death certificates or at autopsy were excluded, as were those where the month of diagnosis was unknown.

All cohort members were Medicare Part A and Part B beneficiaries from diagnosis until death or for at least 9 months. During the study period, claims detailing the specific procedures and noncancer diagnoses were not reported to the Health Care Financing Administration by risk-contract health maintenance organizations, and as a result, patients enrolled in these plans (16% of original sample) were excluded from our cohort.

We searched Medicare claims records for patients who had rectal cancer surgeries performed within 6 months of primary diagnosis and had undergone operations consistent with definitive tumor resection, according to the ICD-9-CM classification system (48.4x, 48.5, and 48.6x). Patients whose claims indicated that they were operated on exclusively for local resection or the creation of an ostomy were excluded. We further selected those who were diagnosed with stage II and III disease using information on tumor size, nodal involvement, and distant spread recorded in the SEER database and classified according to the American Joint Committee on Cancer staging system.

Identification of Adjuvant Pelvic Radiation Usage
The use of adjuvant pelvic radiation within 6 months of surgery was the primary study outcome. We considered that patients who had stage II or III disease and received either preoperative or postoperative pelvic radiation within 6 months of primary surgery had adjuvant radiation treatment. Treatment delivered more than 6 months after primary surgery was not considered adjuvant. Patients who had claims for radiation planning, treatment, or delivery in either the inpatient, outpatient, or physician/supplier Medicare files were considered adjuvant radiotherapy recipients (ICD-9-CM codes V58.0, V66.1, V67.1, procedure codes 9220-9229, common procedural terminology codes 77261-77490, 77750-77797, and revenue center codes 0331-35). Additionally, we examined whether treatment was delivered pre- or postoperatively and whether the patient also received adjuvant chemotherapy.

Patients whose prognosis is so poor that they are unlikely to survive the postoperative period are inappropriate candidates for radiation treatment. Thus, we restricted our analysis to patients who had survived for a minimum of 6 months after surgery. Patients diagnosed with a second malignancy during this interval were also excluded because, in these instances, we could not reliably ascertain whether radiation was administered for adjuvant treatment of rectal cancer or for the second tumor.

Patient Characteristics Associated With Adjuvant Pelvic Radiation
Using information available in the SEER-Medicare files, we evaluated clinical characteristics, including American Joint Committee on Cancer stage (II or III), extent of disease (T2,T3,T4), number of involved lymph nodes, and type of rectal operation (abdominal perineal resection [APR], 48.5; low anterior resection, 48.62 and 48.63; and other rectal resections, 48.4, 48.61, 48.64, 48.65, and 48.69). Patient age at diagnosis, sex, race, comorbidity, year of diagnosis, and socioeconomic status using median income in the patient’s zip code of residence as a proxy were also identified. The association between each clinical and demographic characteristic and radiation treatment was examined, and where significant associations existed, multivariable logistic regression was used to adjust for potential confounding by other clinically important variables.

To examine treatment variation based on the severity of noncancer medical illness, we used Romano’s modification of the Charlson comorbidity index excluding cancer.^10,11 The diagnoses included in the Charlson-Romano comorbidity index include myocardial infarction and diabetes, as well as moderate liver and moderate renal failure, and thus it captures many of the absolute or relative contraindications to administration of adjuvant radiation. We examined all available inpatient and outpatient Medicare claims for the 18-month period extending from 12 months before the index surgical admission to 6 months after surgery, and classified patients according to whether the maximal comorbidity observed was 0, 1, or 2 or greater.

Use of Chemotherapy With Pelvic Radiation
To assess whether radiation was delivered with or without chemotherapy, we examined Medicare claims for medical evaluation for chemotherapy (ICD-9-CM codes V58.0, V66.2, and V67.2), chemotherapy administration (ICD-9-CM code 99.25; common procedural terminology codes 96408, 96410, 96412, 96414, 96520, 96530, and 96545; and HCPCS codes Q0083 through Q0085), and intravenous chemotherapy agents (HCPCS codes J9190 [fluorouracil], J0640 [leucovorin], and J9200 [floxuridine]). Patients who received chemotherapy within 6 months of surgery were considered adjuvant treatment recipients.

Statistical Analysis
To assess the association between adjuvant chemoradiation and patient clinical and demographic characteristics, we compared frequencies using ² tests of significance. We also performed multiple logistic regression with adjuvant radiotherapy with and without chemotherapy delivered within 6 months of the patient’s surgery as outcomes and patient characteristics as predictors. For each variable, univariate analyses were performed as well as analyses controlling for potential confounding by tumor stage, procedure type, comorbidity, age, sex, race, and median income. Patient characteristics were entered into the multivariable regression model according to the categories listed in Table 1. We used the reporting SEER registry to evaluate geographic variation in treatment but excluded location from our final multivariable model because it did not significantly affect our results. Because other variables such as tumor grade and the total number of lymph nodes in the surgical specimen were not independently associated with receipt of radiotherapy, they were also excluded from our multivariate analysis. With a cohort numbering 1,411, we had 90% power (at a 5% significance level) to detect differences in treatment rates of 9% or greater for symmetrically distributed variables, such as sex. However, for asymmetrically distributed variables such as race (58 black patients v 1,237 white patients), we had only 40% power to detect a 10% difference in treatment rates. All P values are two-sided and considered significant at the 0.05 level. SAS software (version 8.0; SAS Institute, Cary, NC) was used for statistical analyses.

	RESULTS

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

Overall, 799 patients (57%) received adjuvant radiation. Radiation was delivered postoperatively for 50% and preoperatively for 7% of patients. Combined modality treatment was delivered to 42% (599 patients) and radiation alone to 15% (200 patients). Only 61 patients (4%) in the cohort received chemotherapy alone, thus indicating that if adjuvant treatment is administered at all, combined modality treatment is standard. Unfortunately, Medicare claims are not consistently detailed enough to identify whether chemotherapy was delivered concurrent with radiation or sequentially, and the precise dose and regimen cannot be reliably ascertained.

The percentage of patients with each demographic or clinical characteristic who received any radiation, combined-modality therapy, or preoperative radiation is listed in Table 2. Table 3 identifies those features that were significantly associated with treatment after controlling for potential confounding as a result of other clinical and demographic attributes in multivariable analysis. As expected, the same characteristics that predict the use of any radiation were predictive of combined modality chemotherapy use.

More patients with stage III disease (66%) than with stage II disease (47%) received radiation, and within each stage group, patients with more advanced T stage were more likely to have had treatment. Patients who had an APR were more likely to receive radiation than those treated with a low anterior resection or other rectal operation. These differences remained significant after adjustment for variation in other patient characteristics (Table 3).

Over 70% of patients in our cohort had no major comorbid illnesses in the year before diagnosis or in the immediate postoperative period. However, patients with higher burdens of comorbid disease used only slightly less radiotherapy, and these differences did not reach statistical significance. The fact that only the healthy elderly are selected to undergo rectal resections and our exclusion of 143 patients who died in the 6 postoperative months may account for the weak association between comorbid illness and use of radiation. Use of other comorbidity classification schema did not change these results.

Although more men received adjuvant radiotherapy than women did (60% v 53%; unadjusted odds ratio, 0.74; 95% confidence interval, 0.60 to 0.91) this was attributable to the fact that women far outnumbered men in the oldest age categories. Therefore, after adjusting for age and other characteristics, sex was not an independent predictor of radiation treatment (Table 3) Only 4% of cohort members were black, and the power to detect differences in treatment rates was accordingly limited. However, overall radiation use rates varied little with race: 57% for whites, 55% for blacks, and 51% for patients from other groups. However, the use of combined-modality therapy was higher for whites (44%) than for blacks (31%) or patients with other racial affiliations.

Treatment rates increased only slightly over the 5-year study period from 54% in 1992 to 57% in 1996. As reported for other cancers, treatment rates varied among the different SEER sites, ranging from 46% in Utah to 66% in Seattle. Patterns of care were not observed to depend on urban versus rural or northern versus southern locations of the reporting SEER registry. Because of the small numbers of patients ascertained from some registries (Table 1), definitive conclusions about regional variation in care cannot be made on the basis of this analysis. There was no strong association between treatment and median income in the zip code tract of residence.

Despite evidence suggesting that preoperative administration of radiation may allow for preservation of the rectal sphincter and avoidance of a permanent ostomy, preoperative treatment seems to have been rarely administered in the mid-1990s. Only 95 (12%) of the 799 irradiated patients were treated preoperatively. This small number of patients precluded identification of clinical or demographic characteristics significantly associated with preoperative treatment, and, therefore, multivariable analyses were not performed, although absolute treatment rates are listed in Table 2. Preoperative radiation may shrink unresectable rectal cancers enough to make surgical removal feasible. Thus, we anticipated higher preoperative treatment rates for patients with T4 tumors. Indeed, preoperative treatment rates for T4 patients were more than double those for patients with T3 lesions (21% v 7% for stage II disease and 13% v 6% for stage III disease, Table 2.) Although patients irradiated before surgery had more advanced tumors, the APR rates were similar for patients receiving radiation before and after surgery (64% v 58%). There was no clear variation in the timing of radiation with respect to age, comorbidity, sex, racial group, or income. Although the absolute rates of radiation increased minimally from 1992 to 1996, the percentage of patients treated before surgery has increased from 5% to 10%, and this trend was significant (P < .001).

	DISCUSSION

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
In a population-based sample of Medicare enrollees diagnosed with stage II and III rectal cancer from 1991 to 1996, we found that 57% received adjuvant radiation. Consistent with the treatment recommendations contained in the 1990 NIH consensus statement, when adjuvant radiation was administered, in 75% of cases, adjuvant chemotherapy was also given. We found that postoperative delivery of radiation is the norm, with over 90% of the irradiated patients receiving treatment after surgery. This exceeds prior estimates of approximately 75%.¹² Evolution of this care pattern in response to mounting evidence that neoadjuvant treatment results in greater sphincter preservation and increased survival outcomes bears ongoing analysis.¹³ Severity of diagnosis was clearly incorporated into treatment decisions because patients with more extensive tumors were more likely to receive treatment.

Although our analysis cannot definitively quantify the extent to which radiation is underused because claims do not reveal patients’ preferences regarding treatment, it does characterize those patients who went untreated. In particular, our results show that treatment rates decline dramatically with increasing age at diagnosis. Our findings underscore the need to identify whether elderly patients’ decisions to forego treatment are informed and consistent with their personal preferences. Alternatively, nontreatment may be attributable to comorbid illnesses or to nonmedical barriers to care such as lack of transportation and absence of supportive caregivers.^14-16 Although poverty may explain why the elderly are less likely to receive treatment, lack of insurance coverage seems to be an insufficient explanation for the age-related decline in use because Medicare insures all patients for radiation therapy. Exploration of the possibility that low treatment rates result from physicians’ beliefs regarding the risks and benefits of treatment for the elderly is clearly warranted on the basis of our findings.

Our results parallel those from a SEER-Medicare cohort of stage III colon cancer patients, which revealed that 55% of patients received postoperative adjuvant chemotherapy and that use was most highly correlated with age at diagnosis.¹⁷ They are also consistent with other studies that have examined the association between age and use of other cancer treatments.^18-23 For example, the use of radiation therapy after breast conserving surgery²⁴ and palliative chemotherapy for metastatic lung cancer also declines sharply with age.²⁵ Because patients over age 75 represent a growing proportion of newly diagnosed cancer patients, further study of treatment outcomes in this population is imperative. Furthermore, our results suggest that clinical uncertainty regarding what constitutes optimal treatment persists when elderly patients are not adequately represented in clinical trials.²⁶

There are limited data on the quality of life for elderly patients who receive radiation for rectal cancer, but available evidence suggests that adjuvant treatment is well tolerated even among the elderly.^27-30 Moreover, there is no upper age limit for recommending treatment contained in clinical guidelines or the NIH consensus statement, and there is no evidence that adjuvant radiation is less efficacious for these patients. Because the purpose of adjuvant radiation is to decrease the incidence of local rectal recurrences, a cause of great discomfort, treatment may be appropriate even for patients with limited life expectancy who might not opt for chemotherapy.

Several limitations of our analysis must be noted. First, the potential for inaccurate coding exists for any claims-based analysis, and clinical information available from billing records is not as detailed as that available from chart review.^31-33 Second, although we used a clinically relevant method to assess comorbidity, we may have failed to identify patients who were judged to be poor treatment candidates based on rare illnesses poorly captured by comorbidity indices or on the basis of limited functional status.³⁴ On the other hand, all of the patients in our cohort were deemed sufficiently fit to undergo major cancer surgery, and all recovered from their operations. Finally, our results cannot be generalized to the approximately 16% of Medicare beneficiaries who received care in a health maintenance organization setting where patterns of care may be different.³⁵ Medical claims do not permit an analysis of the treatment dosages actually delivered, but prior work suggests that when treatment is initiated, completion rates and adherence to standard techniques is high.³⁶

Our claims-based analysis suggests that adjuvant radiation therapy for patients with rectal cancer may not be optimally used. Diminished efficacy, higher comorbidity, greater treatment toxicity, and short natural life expectancies do not provide a clear justification for the decreasing use seen with increasing age. Because adjuvant radiation and chemotherapy provide important and substantial benefit by decreasing local recurrence and improving overall survival, it is recognized as an indicator of high-quality cancer care. For such quality indicators to be useful and to thereby determine the extent to which treatment is currently underused, further research that assesses physicians’ and patients’ knowledge and attitudes regarding treatment is essential.

	ACKNOWLEDGMENTS

 
Supported by a career development award in preventive oncology (no. K07) from the National Cancer Institute (D.S.).

The study used the Linked Medicare-Tumor Registry Database. The interpretation and reporting of these data are the sole responsibility of the authors. The authors acknowledge the efforts of several groups responsible for creation and dissemination of the linked database, including the Applied Research Branch, Division of Cancer Prevention and Control, National Cancer Institute; the Office of Research and Demonstrations, and the Bureau of Data Management and Strategy, Health Care Financing Administration; Information Management Services, Inc; and the SEER Program tumor registries. The authors also thank Joan Warren, PhD, for helpful discussions and Sofia Yakren for her dedicated research assistance.

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Submitted December 27, 2000; accepted May 7, 2001.

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