NcXHF

COMPARATIVE EFFECTIVENESS RESEARCH IN CANCER WITH OBSERVATIONAL DATA
of lymph nodes examined, number of positive lymph nodes,
histologic grade, histologic type; and (4) treatment: type of
surgery and radiotherapy for fırst course of treatment. These
data provide a defınitive source of information on cancer incidence,
staging, and survival. The information on treatment
is less complete. In general, the ascertainment of surgery by
registries is the highest-quality treatment variable. The use of
radiation therapy may be under-ascertained by registries. In
the case of breast cancer, the under-ascertainment has been
reported to be differential by age, income, and other treatment.
11,12 Complete information on chemotherapy administration
is diffıcult to capture; thus, rates of chemotherapy use
are not reported in the SEER database. The SEER database is
de-identifıed, publically available, and free of charge.
Medicare
Medicare is the primary health insurer for 97% of the U.S.
population age 65 and older. The Medicare Claims Data System
collects information on all services provided to Medicare
benefıciaries under its hospital (Part A), supplemental (Part
B), and prescription drug (Part D) insurance plans. Part A
covers inpatient hospitalizations and care in skilled nursing
homes, whereas Part B covers physician services; hospital
outpatient services; durable medical equipment; home health
services; and other outpatient medical services, such as diagnostic
x-rays and laboratory tests. Part D data includes information
on prescription drug use and has been available since
2006. The unlinked Medicare data are comprised of enrollment
fıles and health care claims. These data do not have information
on the dates of diagnosis, stage, histology, or
recurrence, and this lack of registry data has limited the use of
the unlinked Medicare fıles for cancer research. For several
cancer types, such as breast cancer, validated algorithms have
been developed to identify incident cases. 13 The strength of
these data is in studies of patterns of care, geographic variation,
and costs of therapy. To obtain the data set with identifıers,
an application should be submitted to the Research
Data Assistance Center (ResDAC). The cost is dependent on
the specifıc data request.
SEER-Medicare Linked Database
Under an agreement between the NCI and the Centers for
Medicaid & Medicare Services (CMS), patients in the SEER
database who are eligible for Medicare have been linked with
their Medicare records. Of persons who are reported by
SEER as diagnosed with cancer at age 65 or older, 93% were
matched with their Medicare enrollment records. 14 At present,
patients with cancer who were diagnosed through 2011
are linked, and their Medicare claims are available through
2012. For patients with cancer in the SEER database, Medicare
enrollment and eligibility information and a subset of
SEER data are in the Patient Entitlement and Diagnosis Summary
File (PEDSF). The PEDSF also contains census-tract–
level information, including ethnicity, education, income,
percentage English-speaking residents, and population density.
In addition to the registry data provided by SEER, these
data include all billing claims for each patient. The claims can
supplement data from the SEER registry and provide information
on diagnostic testing and additional treatment information,
such as chemotherapy use and patterns of
surveillance. In addition, the data can be linked to the Area
Resource File and the American Medical Association’s Physician
Masterfıle, which can provide additional information
about health resources and physician characteristics, respectively.
These data do have some substantial limitations. First
and foremost, these data are administrative data generated
for billing, so they lack the detail of clinical data. The claims
are only complete for those patients in the fee-for-service
plans (rather than in the HMO plans) and do not capture
services provided by the U.S. Department of Veterans Affairs.
Finally, as with the SEER data, cancer recurrences are
not captured. To obtain these data, an application must be
submitted to the NCI for review. Cost estimates can be found
on the SEER-Medicare website. 15 All publications resulting
from these data must be reviewed before publication to ensure
that patient confıdentiality is protected.
SEER–Medicare Health Outcomes Survey Linked
Database
The SEER–Medicare Health Outcomes Survey (MHOS) data
set is a linkage of two large population-based databases. The
SEER database, described above, has been linked with the
MHOS, which is a large survey of health-related and qualityof-life
information among participants in the Medicare Advantage
Organization. These data include information on 12
cohorts of baseline and follow-up surveys at 2 years, which
were conducted between 1998 and 2011. 16 Collected data include
patient demographics, marital status, income, smoking
status, chronic conditions, and health-related quality of life.
From 1998 to 2005, the MHOS used the 36-question shortform
(SF-36) to collect data on health-related quality of life,
but the MHOS switched to the Veterans RAND 12-item
health survey (VR-12) in 2006. This data set provides additional
patient-reported information to the SEER data. However,
the survey was not limited to participants with cancer
nor timed with a diagnosis of cancer, therefore the small sample
sizes may limit potential analyses.
SEER–National Longitudinal Mortality Study Linked
Database
The National Longitudinal Mortality Study (NLMS) is a data
set that includes sociodemographic data collected by the
Census Bureau by in-person and telephone interviews, and it
includes cause of death information. The variables include
race/ethnicity, education, income, employment, occupation,
smoking, health status, and health insurance status. These
data have been linked with SEER and with Medicare claims
and can be used in studies evaluating socioeconomic determinants
of cancer and cancer outcomes or outcomes related
to income or employment, in addition to other uses.
Commercial Claims Databases
There is an increasing number of databases that can be licensed
for research on the commercially insured population.
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