Managed Care and Cancer Outcomes for Medicare Beneficiaries With Disabilities

In 2005, 1 in 6 Medicare beneficiaries (6.5 million persons) was entitled to receive Medicare benefits because of disability.¹ Medicare beneficiaries with disabilities seem to be at risk for increased cancer mortality,² even when diagnosed at the same stage or at an earlier stage, compared with persons without disabilities.³ In addition, persons with disabilities may receive different cancer treatment than persons without disabilities.^2,4

Medicare beneficiaries may receive care within a health maintenance organization (HMO) or within the fee-for-service (FFS) sector. It is uncertain whether the type of health insurance arrangement (HMO vs FFS) affects the quality of care for Medicare beneficiaries with disabilities.⁵ In some studies,^6,7 beneficiaries with disabilities were less satisfied with managed care plan performance and were more likely to disenroll. However, other evidence indicates that beneficiaries with disabilities receiving care in HMO plans perceive better access to primary care services and greater affordability of health services than those with traditional Medicare coverage.⁸ Medicare beneficiaries who are enrolled in HMO plans are more likely to undergo cancer screening,^9-12 generally have cancers diagnosed at an earlier stage,^13-16 and may have improved survival.¹⁴

The Surveillance, Epidemiology, and End Results (SEER) cancer registries merged with Medicare data have been used to study health disparities among persons with disabilities.^2,3 We used merged SEER-Medicare data to evaluate whether the type of Medicare insurance arrangement (HMO or FFS) affects cancer outcomes for Medicare beneficiaries with disabilities. We studied 2 high-volume cancers, breast cancer and lung cancer. We chose breast cancer because it is amenable to screening and because experiences of these patients would capture potential disparities in early detection and treatment. In contrast, screening is not recommended to detect lung cancer, although surgery and radiation treatment may improve survival.^17,18

METHODS
Data Sources
We used the SEER-Medicare dataset, which links SEER registry information to Medicare claims data.^19,20 SEER consists of 11 population-based tumor registries representing approximately 14% of the US population.²⁰ SEER collects patient information on demographic characteristics, primary tumor site, stage at diagnosis, tumor size, histologic findings, tumor grade, hormone receptor status, initial course of treatment, and vital status. SEER tracks vital status annually, and death certificates are used to capture underlying cause of death.

Study Sample
We identified all persons 21 years and older within the SEER-Medicare dataset having a pathologically confirmed first diagnosis of breast cancer (n = 62,315) or non–small cell lung cancer (n = 55,770) from January 1, 1988, through December 31, 1999. We then restricted our sample to those persons who originally qualified for Medicare coverage because of Social Security Disability Insurance (6839 with breast cancer and 10,229 with lung cancer). Therefore, our sample includes persons younger than 65 years who have Social Security Disability Insurance and persons 65 years and older whose Social Security Disability Insurance has been automatically converted to Old Age Survivors Insurance. As described elsewhere, we focused exclusively on individuals with Medicare when newly diagnosed with cancer, eliminating persons disabled by cancer.³Medicare data indicate for each month whether persons were eligible for Part A and Part B and whether they were enrolled in an HMO insurance arrangement. To examine possible effects of insurance structure on early detection of cancer, we constructed a variable that defined insurance arrangement before diagnosis. We determined the type of insurance arrangement during the month of diagnosis and the previous 12 months. For this period, we assigned cases to 1 of the following 3 insurance categories: FFS for persons continuously enrolled in traditional FFS Medicare, HMO for persons continuously enrolled in HMO plans, and mixed FFS/HMO for persons enrolled in both FFS and HMO plans during the period. To examine treatments following diagnosis, we designated similar postdiagnosis insurance variables for persons continuously eligible for Medicare Part A and Part B during the month of diagnosis and the 6 months after diagnosis (or until death if survival was <6 months). For analyses of survival, we assigned cases to similar insurance categories covering the prediagnosis and postdiagnosis periods combined.

Stage at Diagnosis
SEER determines stage at diagnosis based on a combination of pathologic surgical and clinical assessments available within 2 months of diagnosis.²¹ Stage at diagnosis is recorded using the American Joint Committee on Cancer (AJCC) staging system (stage 0, I, II, III, or IV). In our analysis of stage at diagnosis, we excluded persons whose cancers were unstaged (346 with breast cancer and 1182 with lung cancer).

Cancer-directed Treatments
SEER collects information on the initial course of treatment, which was defined as all cancer-directed treatments within 4 months of diagnosis from 1973 through 1998 and within 12 months of diagnosis after 1998. Ascertainment of surgery and radiation therapy by SEER is generally complete.^22,23 However, ascertainment of chemotherapy is incomplete and is not included in the SEER-Medicare–linked dataset. SEER does not collect information on prediagnosis screening tests such as mammography. We relied solely on SEER information to define cancer-directed treatments because Medicare claims are unavailable for persons having HMO insurance.

We defined breast-conserving surgery as segmental mastectomy, lumpectomy, quadrantectomy, tylectomy, wedge resection, nipple resection, excisional biopsy, or partial mastectomy that was not otherwise specified. We defined mastectomy as subcutaneous, total (simple), modified radical, radical, extended radical mastectomy, or mastectomy that was not otherwise specified. We examined frequency of breast-conserving surgery among women having AJCC stage I, II, or IIIA cancers. We further examined the following 2 secondary outcomes related to quality of care: (1) receipt of axillary lymph node dissection and (2) receipt of radiation therapy among women who undergo breast-conserving surgery. Sentinel lymph node biopsies, a recent innovation, are not reported in our database.