Measuring Quality of Life: 1995 Update
Measuring Quality of Life: 1995 Update
The term quality of life (QOL), or health-related quality of life,
has emerged to organize and galva nize a collection of outcome
evaluation activities over the past two decades in cancer treatment
research. Prior to this, length of survival was considered to
be the only primary outcome in oncology treatment research. Recently,
however, progress in increasing survival has been slow, and at
times has exacted considerable cost .
It is now widely accepted that in most circumstances quality of
survival is as important as quantity of survival. This implies
that a severely toxic treatment must be evaluated for its detrimental
impact as well as its survival benefit. It also raises a less
obvious point: that treatments can be considered efficacious if
they improve the quality of life even in the absence of survival
benefit. Thus, investigating the impact of cancer treatments on
QOL is a two-tailed enterprise where treatment toxicity is traded
not only with survival time but also with post-treatment function
QOL evaluation entails a multidimensional quantification of patient
functional status, usually as perceived by the patient. In the
decades to come, treatment intensification strategies which increase
toxicity are likely to continue, given the advent of hematopoietic
growth factors and improved antiemetic regimens. This further
increases the importance of evaluating toxicity, patient function,
and patient preferences for treatment. QOL evaluation differs
from classical toxicity ratings in two important ways:
1. It incorporates more aspects of function (eg, mood; affect;
social well-being) than those which have typically been attributed
2. It focuses on the patient's perspective.
The United States Food and Drug Administration has stated that
benefit to quality of life (QOL) is one of two requirements for
approval of new anticancer drugs . The other, of course, is
improved survival. Given the incurability and increasing chronicity
and prevalence of many forms of advanced cancer, the QOL endpoint
has become very important. Industry has thus joined hands with
the caring clinician in an unusual marriage, promoting supportive
care and symptom relief in the name of quality of life.
Despite general acceptance of the value of assessing quality of
life during cancer treatment, relatively few clinical trials actually
include a QOL component. For example, fewer than 5% of clinical
trials reviewed as of 1982 by the Department of Health and Human
Services studied QOL . A 1986 survey of surgical trials revealed
that only 3% had systematically evaluated QOL . In 1995, 15%
of the currently active Eastern Cooperative Oncology Group (ECOG)
trials include a QOL component. Although there are some prevailing
attitudes which devalue the role of quality of life investigation
in clinical trials, a larger obstacle to successful QOL research
has to do with difficulty coordinating the social and medical
sciences in a clinical setting.
Recently, however, developments in health-specific quality of
life methodology have made accurate QOL evaluation a possibility.
Dozens of measures, many of which are both practical and valid,
have emerged over the past decade and are available for use. This
paper discusses issues in the selection of patients and measures
when studying quality of life during cancer treatment.
One of the purposes of this publication is to clarify the extent
to which we can agree on a definition of quality of life as it
applies to people with cancer. The closer we can come to agreement,
the more likely we will be to prevent the use of inappropriate
measures leading to inaccurate and confusing conclusions. Coming
to agreement about a definition does not mean selecting one or
a single set of measures; there is no "gold standard,"
and there cannot possibly be one until the construct as it applies
to cancer is clarified. Even then, it would probably be unwise
to name a gold standard; that would risk allowing the tail to
wag the dog. As soon as a measure is accepted as complete, the
investigator surrenders the opportunity to assess components not
included in the scale even if they have major implications for
QOL. For example, although most QOL scales measure common physical
problems such as pain and nausea, most do not measure confusion.
Confusion may be the linchpin of quality of life in a patient
with a brain metastasis, or whose calcium level cannot be controlled.
Should a QOL scale therefore measure confusion?
The same question could be asked of dozens of other clinical problems.
If the decision about inclusion of an item into a quality of life
scale was based upon the possibility that it could be important
for any cancer patient, the gold standard scale would be very
long indeed. Instead, the probability of occurrence and the relative
importance of the item in the overall scheme must prevail. The
modular approach, as described by the European Organization for
Research and Treatment of Cancer (EORTC) QOL Working Group [5,6]
and by Cella and colleagues [7-9], in which a core of general
questions is supplemented with disease- and treatment-specific
items, is a method for addressing this dilemma.
In their classic volume, Campbell and colleagues  describe
quality of life as: "a vague and ethereal entity, something
that many people talk about, but which nobody very clearly knows
what to do about." While it may ring true, this description
is a nightmare for the test developer. Some have suggested abandoning
the term quality of life because it is too general to have meaning.
Other less nihilistic observers have pointed out that because
the current definition of the term is so vague, it has been exploited
as a marketing tool . There is a consensus of opinion, at
the very least, that QOL is multidimensional [5,11-14].
The integrity of the term quality of life has been justifiably
challenged on the grounds that it cannot be validly measured because
it means so many different things to so many different people.
With respect to both content and construct validity, this is certainly
true. Until one has a clear definition of the concept, including
its component parts if applicable, one cannot determine whether
a scale is validly measuring that construct. The first step toward
successful assessment of QOL in the clinical research setting
is to clarify its definition and component dimensions.
We had earlier developed a working definition of quality of life
which laid the groundwork for measurement: "Quality of
life refers to patients' appraisal of and satisfaction with their
current level of functioning as compared to what they perceive
to be possible or ideal."  This earlier definition
was modified to explicitly incorporate the multidimensionality
of QOL: "Health-related quality of life (QOL) refers to
the extent to which one's usual or expected physical, emotional,
and social well-being are affected by a medical condition or its
As the initial definition implies, it is important to obtain an
appraisal of the extent of dysfunction as well as a rating of
how this appraisal matches expectations. The appraisal itself
is important because it documents the patient's report of actual
dysfunction. The expectation rating is important because it provides
the patient's opinion as to whether that dysfunction is tolerable.
Some patients with minimal actual disability are extremely dissatisfied,
while others seem quite able to tolerate severe impairment and
may even feel fortunate to be obtaining therapy. Many decisions
about treatment are best made with this knowledge.
Patients' perceptions of their illness are extremely variable,
and factors other than actual disability enter into that perception.
For example, bedridden status may be more upsetting to an adolescent
receiving bone marrow transplantation than to an older adult with
a history of chronic arthritis. For the adolescent, bedridden
status represents a 100% decrease in normal activity level. For
the older adult who could never expect to be fully ambulatory
because of preexisting arthritis, the bedridden status represents
less than a complete loss of possible ability. To assume that
the same actual activity level in these two individuals would
reflect comparable quality of life would be an obvious error.
A more subtle example is the presence of sexual dysfunction in
a couple with an active and unconflicted sexual history, compared
to the same dysfunction in a couple with a premorbid history of
marital conflict and sexual difficulties. To the former couple,
the same level of actual dysfunction would likely be more disruptive
because it deviates more dramatically from their history. For
the couple with premorbid sexual dysfunction, it is unwise to
assume their difficulty can be attributed to cancer treatment.