Evaluating Medical Claims and Data

Last update: 06/07/2011

Without standards for evidence for the approval of new drugs,
we'd have many thousands of choices (some helpful, some ineffective, and most harmful)-- with no basis for making a helpful choice, and no foundation on which to make real scientific progress.

Unfortunately observation can fool us, as in this historic example:

"For many centuries doctors used leeches and lancets to relieve patients of their blood. They KNEW bloodletting worked. EVERYBODY said it did. When you had a fever and the doctor bled you, you got better. EVERYONE knew of a friend or relative who had been at death’s door until bloodletting cured him.

Doctors could recount thousands of successful cases."

Why We Need Science: “I saw it with my own eyes” Is Not Enough 

The importance of trying to see things as they are:

Our goal is to help patients and caregivers better evaluate medical claims - to better recognize information that is not plausible or is weakly supported.

How do we start? 

By questioning the information we receive and by recognizing factors that can distort medical claims and scientific findings.  By referring when possible, to the source documents and being skeptical of interpretations of others.   By recognizing common sources of bias, such as having a financial conflict of interest.

Bias: different reasons for different groups:

"Bias" has two meaning:  

(1) "an inclination of temperament or outlook; especially: a personal and sometimes unreasoned judgment." Bias can influence how one looks at outcomes, or in what we choose to read or ignore. 

(2) In a study design, a bias is defined as an error in the method of study that leads to a deviation in the outcome away from the truth.

Sources of Bias:

Financial conflict of interest 

Wikipedia: "A conflict of interest is a situation in which someone in a position of trust, such as a lawyer, insurance adjuster, executive or director of a corporation or a medical research scientist or physician, has competing professional or personal interests. Such competing interests can make it difficult to fulfill his or her duties impartially. A conflict of interest exists even if no unethical or improper act results from it. A conflict of interest can create an appearance of impropriety that can undermine confidence in the person, profession, or court system."

Conflicts of interest occur when personal, professional, or financial interests intentionally or unintentionally influence decisions on scientific methods, or how data from the study are interpreted. 

"A financial conflict of interest, I believe, is any financial association that would cause an investigator to prefer one outcome of his research to another. Let me give you an example. If an investigator is comparing drug A with drug B and owns a large amount of stock in the company that makes drug A, he will prefer to find that drug A is better than drug B. That is a conflict of interest."   ~ Marcia Angell, M. D. Source: ohrp.osophs.dhhs.gov

Those who develop new drugs or sell supplements have an inherent financial conflict of interest with respect to objectively evaluating the true worth and benefits of their products or services, which can lead to selective reporting or "hyping" the products in order to maximize shareholder confidence and the profitability of the company that sells them.

Scientists who have financial interests in products or services must disclose these relationships, which make them inherently less able to overcome the biases these monetary interests can create. 

"While most people think conflicts of interest are a problem of overt corruption, that is, that professionals consciously and intentionally misrepresent the advice they give so as to secure personal gain, considerable research suggests that bias is more frequently the result of motivational processes that are unintentional and unconscious " ⁴

Consider that, by investing in a company, a scientist may demonstrate a belief in the value of its product, perhaps in advance of evidence. Scientists have an ethical responsibility to avoid arriving at conclusions ahead of time. The discipline of science requires that theories be tested in well-controlled studies, and that the outcomes be evaluated objectively before conclusions are made.

ASK:  

- "Was as the research funded by an organization that generally advocates a specific point of view? 

- Do the findings of the research parallel the organization's point of view - or too closely?" ²

Reporting bias: 

Because of personal inclinations, expectations, or other biases, a participant in a study may report events more favorable to the hypothesis, and leave out, or not see, events that contradict it. There is also the potential for this type of bias in case reports

Selection bias:

Investigators may introduce bias into a study by selecting patients who have characteristics (such as young age) that are favorable to a desired outcome; and also by excluding patients who do not (such as patients with low blood counts). Randomized studies protect against this kind of bias.

ASK:

- Was the data source manipulated to produce analyzable data? 

- Was the data source selected with an unusual methodology? 

- Was the data source unusually small or narrow, or tightly controlled by the researcher?

- Was the data source self-selected (not random)? 

Intellectual/confirmation bias:

Investigators and scientists can develop unintended prejudices about the value of their own work, ideas, or intellectual property. 

Investigators may unconsciously see benefit when none exists, or they may set up a study in ways more likely to reveal weaknesses, exaggerate the benefits, overlook unanticipated side effects, and so on.  

I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives.” 

~ Leo Tolstoy

ASK: 

- Is the researcher affiliated with an organization that promotes a specific point of view?

- Does the researcher produce studies that consistently generate the same conclusions? ²

- Is the research group the ONLY group interested in the research question?

Confirmation bias is the tendency to give more weight to incidents and data that conform to preexisting beliefs and to forget things that do not. 

"We're all prone to it, including scientists. One major advantage of the scientific method is that it is pretty good at overcoming confirmation bias."  Source: http://scienceblogs.com 

Biases common to patients and caregivers:

Denial: In order to cope with living with a life-threatening disease, patients or caregivers may develop a tendency to minimize the dangers of the disease, or to inflate the potential of alternative and other less toxic approaches to control it. Denial can lead to missed opportunities and delays that can make the disease more difficult to treat.

Fear: To be fearful of a cancer or cancer treatment is to be human, and sometimes it's justified. In patients, the fear of the toxicity associated with many standard cancer therapies can form a bias in favor of claims made for safer alternative, or even investigational low-toxic therapies.  

We are highly prone to wishful thinking.    

Physician biases (reasons to consult independent experts):

Even a trained oncologist can have conflicts of interest, biases, or gaps in knowledge - especially if he or she does not specialize in lymphomas. 
 
Investigators may have intellectual biases about any therapies they may be testing. 

Community doctors might have biases in favor of what is easiest to administer. 

HMO physicians may prescribe what is least expensive. Other doctors might be influenced, perhaps unconsciously, by sales promotions from the drug industry. 

Patients expressing their desire to continue working without interruption may influence a busy physician to prescribe what meets the immediate needs, without fully discussing possible negative long-term implications of that treatment decision.    

References and Further Reading: 

1.       For a readable and concise paper on scientific integrity ethics.ucsd.edu 

2.       Potential Sources of Bias  ascd.org   pdf

3.       The Dirt on Coming Clean: Perverse Effects of Disclosing Conflicts of Interest cbdr.cmu.edu .pdf

4.       Identifying Your Biases: wpas-rights.org 

"It is important to recognize your biases, and to periodically evaluate whether they are interfering with your judgment.  The first step to not letting bias interfere with your judgment is to accept that it's there and decide to deal with it."

Associations: Cause and Effect?  

Did an action lead to an outcome?  ... or was it coincidental?

An association is an observation that one event or condition occurs with another. But associations do not mean one thing caused another. That is, associations do not prove causality - the relating of causes to the effects they produce.

Example A:
Suppose a survey shows that that people who drink wine live longer than those who drink beer.

 

We might be tempted to interpret this association to mean wine is better for you than beer.  However, it may be that people who choose wines are more likely to eat healthier foods, or that foods that go well with wine are better for you than foods that go well with beer. 

So the chips and pizza are confounding variables and the study does not yet prove causality: the consumption of wine might not influence health one way or the other.  

Example B:
There's a likely association between people who wear crash helmets and brain injury.

 

However, it's easy to recognize it's the high-risk activities of folks who must wear helmets that increase risk of brain injury, not the helmets.

Example C:
In any study, better outcomes may be observed for people born in August or January.

 

The last example obviously explained by chance.

 

Forming conclusions that A caused B can range from harmless to dangerous: 

 

Harmless, when a baseball player hits a home run and recalls that he had eggs for breakfast that day - who then continues to have eggs on game days.

 

Dangerous, when a patient delays a needed treatment based on anecdotal reports (an association taken as fact) that use of an herb can control the disease.

 

However, observations and exploring possible connections between events (forming hypothesis) is the starting point of science - inspiring further research and well-controlled experiments that prove or disprove it. 

 

Since random associations are so common, plausibility is required before expensive research would be done.  For example, it would be foolish to study the effects of birth dates on outcomes, or to test if minute fractions of a compound - too small to measure - could have therapeutic effects on human disease.   See Homeopathy discussion.

Here are some common assumptions about cause and effect related to indolent lymphoma, kept alive by testimonials:

1 Patients with indolent lymphomas may be particularly susceptible to confusing cause and effect, because the natural course of the disease is so variable. It may remain stable for many years without any intervention, or regress spontaneously "as many as 20% to 30% of patients will experience regressions at some time in the clinical course of their disease."  

Therefore, if a practitioner prescribes a life style or alternative protocol that 100 patients follow, as many as 30% are likely to do well because they would have done well anyway. This "effect," - which has good probability of being unrelated to the practice - will often result in strong belief and promotions, as in: "How can you argue with my success?"

2 Lymphoma is sensitive to many treatments and has a variable natural course - can wax and wane independent of therapy.  The proof that an assay can predict response would therefore require controlled studies on many patients over time - some selected by assay, some selected by empirical data.    

Practitioners have an obligation to state that their ideas and practices have not been proven to provide benefit or predict outcomes. 

Vaccines and Autism link:
It's easy to confuse correlation with causation, by Tony L. Hines

Regarding preliminary scientific reports:  

John Godfrey Saxe's version of an Indian parable applies to the quest for understanding - and actually understates the complexity of human biology and drug interactions, thousands-fold. 

It was six men of Indostan
To learning much inclined,
Who went to see the Elephant
(Though all of them were blind),
That each by observation
Might satisfy his mind.

The First approached the Elephant,
And happening to fall
Against his broad and sturdy side,
At once began to bawl:
"God bless me! but the Elephant
Is very like a wall!"

... http://en.wikipedia.org/wiki/Blind_men_and_an_elephant
 

Subset analysis ... (a target shooting analogy)

Larry wrote: 

The drug failed to achieve the primary goal(s)/ endpoints the researchers (and drug company) set for themselves ahead of the clinical trial.

By slicing and dicing the data after the fact, in a small subset of the patient cohort, they drew statistically iffy conclusions that served their argument.

As some wag once put it:

After-the-fact sub-set analysis is like shooting at a barn, then painting bulls-eye around the bullet hole, where ever it happened to be.  ... Hardly compelling "proof".

Careful patient advocacy requires that we be able to tell the difference between
marketing hype of companies with clear financial interests and cases where
regulatory hurdles are keeping back a truly valuable drug from the patient
community.

The drug in question is hardly a good example for getting the patient community
mobilized.


 

Subset analysis - an example  http://bit.ly/mwHalt This subgroup analysis suggested that the treatment was quite effective and statistically significant for all patients except those born under the sign of Gemini or Libra. The difference in outcome with respect to astrologic sign was naturally an artifact and would not be reproducible in subsequent studies. This was the point of their analysis.

Baseball and the FDA:

Pitchers often believe every close pitch is a strike and that the strike zone is too small.  So just as we recognize the need for a neutral party to call balls and strikes in baseball, we should also recognize the more urgent need for an impartial agency, such as the FDA, to evaluate claims of medical benefits and risks.  

In order to test claims the drug sponsor must conduct well-designed studies that minimize bias and demonstrate safety and efficacy for a given condition.  Absent evidence-based tests and assessments we'd return to a  "Wild West" environment with no means of making informed or safe medical decisions, and no good foundation on which advances in clinical science could be made. 

Is the FDA without bias and conflict of interest?  

No agency or human being is completely free of bias, but the agency is committed and mandated by law to achieve impartiality. There are strong policies on ethics and conflicts of interest in place, and criminal penalties can be invoked for violations of these regulations.

About FDA's Ethics Program: "The Agency’s ethics program is administered to help ensure that decisions made by Agency employees are not, nor appear to be, tainted by any question of conflict of interest. The "ethics" laws and regulations were established to promote and strengthen the public’s confidence in the integrity of the Federal Government. The Agency’s Ethics and Integrity Branch provides advice and assistance to FDA employees on a variety of ethics related matters including, but not limited to, financial disclosure, prohibited financial interests, outside activities, co-sponsorship agreements, and post employment."

See FDA.gov/opacom/ethics/ 

Billiards and Clinical Trial Design: 

Retrospective versus Prospective trial designs

There are two basic types of studies: retrospective and prospective.  Understanding each can help the patient advocate to better converse with scientists on drug development and assessment ... and help consumers (all of us) to evaluate the strength of evidence in scientific reports, and other medical claims.

A patient advocate provided a nice analogy to help compare retrospective and prospective studies: 

"Shoot a cue ball into a pack of billiard balls and the 7 ball goes in the side pocket. A retrospective analysis *looks back* at the shot with the objective of finding evidence that guides how to play pool to win. The prospective study, on the other hand, starts with a hypothesis and tests it going forward: "I will shoot the ball into the pack this way, and I predict the 7 ball will go in the side pocket." So with a prospective study you must call your shot in advance.

Thus, the prospective study provides a much higher level of confidence that the outcome was determined by the action (that is was causal), and can be repeated ... that it was not the result of chance or other factors.  

Is the results of a single prospective experiment sufficient evidence? Generally not, unless the findings are "robust." Most often a second experiment will be needed to validate the first. You also want to scrutinize the DESIGN of the experiment to see if it contains BIASES (study flaws) that may have "rigged" the outcome. ... Perhaps the 7-ball was put near the side pocket, or the table slants that way. 

An example of bias in a clinical trial is when investigators select "ideal" patients that have a favorable prognosis (good counts, young age) ... or they don't count participants in the analysis who died from "unrelated" causes, or they do not give sufficient weight to side effects ... 

The main purpose of doing controlled experiments is to achieve an acceptable LEVEL OF CONFIDENCE that the positive effects measured in the experiment predicts what will happen to patients in the real world. The alternative to this expensive process is to rely on OPINION ... a return to the dark ages.

Importantly, there is never absolute certainty in these matters. Statistics is about measuring the level of certainty that an outcome in an experiment predicts outcomes for the rest of us ... so that we can have confidence that making a new drug available for an indication (cancer, diabetes, osteoporosis) is on balance better for the patients afflicted with the disease than no treatment, or an existing treatment. 

So the billiard table analogy is useful but it oversimplifies. A clinical trial is many times more complicated. For example: what is the outcome that you are measuring (the end point), and how well does it predict clinical benefit? Does tumor shrinkage increase survival, or outweigh the risk bone marrow toxicity? Does an increase in time to progression offset the long-term risk of secondary MDS? Does the intervention improve overall survival or quality of life? Thus, the indication (cancer versus a cold), and what's already available to treat it, has a lot to do with how much risk is acceptable for the new drug.

Not surprisingly the drug sponsor will have a bias, because they are driven to do this difficult work in order to realize a profit. So the industry is prone to setting up, interpreting, and reporting on the experiment in ways that favor the benefit side of the equation.

Please note, however, that the PROFIT motive is ESSENTIAL to the process and to progress Without it new drugs would NEVER be developed or tested. We need all of these: the profit incentive, rigorous scientific method (controlled prospective studies), patient participation, and independent and impartial FDA review. 

The barometer that we are heading in the right direction in general is an increase in life expectancy, and overall survival (OS) for various indications: Note the recent improvements in OS for indolent follicular NHL.

The purpose of conducting well-design trials is to avoid the many dangers of practicing medicine based on opinion. We want to be sure that an intervention - for a specific condition - provides clinical benefit. ...

For example, without use of a controlled study, Hormone Replacement Therapy (HRT) would still be a common practice today ... and, contrary to what was anticipated based on case observation and theories, we would still be giving these hormones to women, increasing the risk of heart disease and cancers. 

Finally, importantly, with opinion-based medicine we would have no scientific foundation to build on. With the value of drug A based on opinion (observations and theory), we could not reliably compare it to drug B, or evaluate how prudent it is to test drug C with drug A. 

Take away standards for approval -- as the Abigail Alliance appears to advocate for -- we would soon be victimized by claims, counterclaims, sales pitches, and promotions of inadequately tested drugs. Drugs would be released into the market with insufficient safety and efficacy information. Gathering this information is very much more difficult after marketing - and that absent standards of evidence for the release of new drugs, the difficulty would increase exponentially.  

Is anyone's perspective more believable?

Perhaps we can learn quickly from the perspectives of doctors and scientists who have cancer, as the threatening nature of the disease is likely to remove any financial biases they may have had in respect to the integrity of the drug evaluation system in America. 

"Patients who don’t understand the difference between information based on theory, anecdote, historical analysis, or double-blind placebo controlled studies are making ill-informed decisions, believing alternative therapies are safer or more effective when they are not. 

Even patients who presume that alternative therapies are ineffective may use them. Why? When faced with a life-threatening disease requiring highly toxic treatments with no guarantees, or when dying because there are no effective conventional treatments, it takes guts to reject something or someone claiming to be able to save you, just in case you might be wrong."  -  Wendy S. Harpham, MD (NHL survivor) Full text: amcancersoc.org

Conspiracy theories are often used to promote unorthodox therapies 

Please consider that such a conspiracy would require the complicity of many thousands of scientists, doctors, and regulators - who also get cancer and spouses, parents, grandparents, children, and loved ones also get cancer. 

Quackery and Charlatanism:

Patients with lymphoma are particularly vulnerable to believing in easy, risk-free remedies. 

The charlatan or quack has a message that appeals to wishful thinking and also our desire for certainty, which is an easy message to craft when unencumbered by the truth ... or an objective test that a theory actually works and provides clinical benefit.   

In medicine - as in life - benefit is not often achievable without risk, and outcomes are rarely certain.  Unlike the charlatan, the trained doctor is obligated to provide accurate information that is based on published clinical studies, which will describe both risks and benefits, relative to the disease untreated or treated differently.  

Red flags of quackery: 

 
See also our printable Red Flags and Free Speech PDF
 

Related Resources:

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Terminology to help you assess clinical data and medical claims:

"All scientific work is incomplete - whether it be observational or experimental. 
All scientific work is liable to be upset or modified by advancing knowledge. 
That does not confer upon us a freedom to ignore the knowledge 
we already have or postpone the action that it appears to demand at a given time. "
 - Sir Austin Bradford Hill (1965)
 

Abstracts | Theory | Treatment Response | Statistical Significance (p-value & confidence)
 

Abstracts:

Abstracts are summaries of larger papers and therefore do not contain all the available details of the study methods and data.  

Abstract conclusions may not be accepted by experts in the field. Reputable peer-reviewed journals sometimes require modifications to conclusions from the original abstract for this reason -- or they may reject the paper from publication because it was determined that the methods (methodology) or data did not support the conclusions made in the abstract. 

Therefore, it's important to avoid forming conclusions on the basis of abstracts.  They should be considered only a starting point for discussions with your doctors and perhaps a basis for additional inquires and research.  

Linda writes: "I think it's important to note that one must be very cautious in drawing conclusions from merely reading an abstract. It's important to read the full article, understand the methodology, and the strength of the statistics and research design to determine if the conclusions the authors present in the abstract are reasonable. The better the journal -- and the higher the quality of the peer review necessary to be published in the journal, the more likely the methods and design, etc. will be good. Even with that, I've seen some questionable studies get into good journals." - L - (NHL-survivor & medical professional) 

Questions to ask: 
 
1) Was the paper published in a respected journal? 
 
2) What types of studies and methods were used to reach the conclusions? 
 
3) Do papers published by other groups support the conclusions?  

Reproducibility is valued in science, especially when a finding comes from a different investigative group. The reason for this is that it reduces the chance that bias, or choice of methods, or chance influenced the findings or the conclusions.

Key:  start by asking questions of (not just accepting) the information we receive.
 

Theory (Hypothesis)

"A hypothesis consists either of a suggested explanation for a phenomenon (observable event or, quite literally, something that can be seen.)" wikipedia.org

Theories are starting points for experiments and studies. They should not be regarded as a proof, no matter the reputation of the author. When someone tells you that this is how a treatment works and that it is therefore desirable, you might ask:  
 
   What clinical data supports the theory?  
 
   Who published the findings, and in what journal?  

Evidence-based medicine requires that a theory - the hypothesis - be tested objectively ... 
in a way that minimizes biases - that the pool table is not tilted in a way that favors the theory.  

Treatment response

Describes clinical outcomes from therapy based on a clinical change, such as the reduction in size of a lymph node.  Responses, however, may or may not result in meaningful clinical benefit - defined as improved survival or the reduction of symptoms.

For example, with lymphatic cancers the lymph nodes can increase and decrease in size because of transient inflammatory reactions, which could lead to false assumptions about the benefit of a drug or a life style intervention.   Also, the reduction in tumor size might be offset by the short or long-term toxicities of the drug. 

Some questions to ask about response: 
1) How long was the response? 
2) At what intervals were the outcomes measured and with what tests? 
3) Did the measured response correspond to clinical benefits?
4) Who reported the responses and were the outcomes verified by independent reviewers?
5) How large was the patient sample, and how were they selected? 
6) What is the expected clinical course of the disease?
7) What were the short or long-term toxicities (the costs) relative to other treatments?
 

Mean (average), Median (middle), Mode (most common)

Mean (average) - the total of all numbers included divided by the quantity of numbers represented.  

Median - the number midway through an odd set of numbers or 
a value halfway between the two middle numbers in an even set.

Mode - the number or value that occurs most frequently in a series. 
If two or more values occur with the same frequency, then you take the mean of the values.

Adapted from http://www.unc.edu/depts/wcweb/handouts/statistics.html 

Note: These calculations are meant to provide information based on the study sample for  comparison purposes, not to predict individual outcomes.  The significance of these calculations depending on other important questions as described below:

Survival curves - the basics  http://cancerguide.org/scurve_basic.html

"You will often find survival curves inhabiting technical papers in the medical literature, and some understanding of these curves is essential to understanding the technical literature."

Statistics (a primer):

The purpose of statistical analysis is to tell us how likely the finding in the experiment predicts outcomes in the real world.   Was it fully or partially due to chance?  What is the level of confidence?

Important questions to ask:

About statistical significance: 

In order to draw better conclusions about data we need to know just a little about measures of statistical significance, which I think of as a level of certainty that an outcome was not due to chance.  

So, hypothetically, if you gave two groups identical placebo therapies there would be a difference in the outcome - even if those two groups were quite large. That is, by chance one or the other group will do better given identical drugs because by chance they will have higher or lower risk disease, or capacity to heal, and so on. . So it's very common to see what looks to be a sizable difference in a study outcome be described as "no significant difference." 

"Statistical conclusions, about responses to treatment in a small group of patients for example, are not absolute.  Everything is possible, but some things are very possible, some are less possible and others are very unlikely -- but still possible to occur. 

We draw conclusions with a certain amount of confidence, conventionally 95% or 99%, 
but there is still some chance of an error (5% or lower)." Source: stanford.edu  

Margin of Error - Confidence

We might just look for two measures of statistical significance in scientific reports to quickly estimate the strength of the finding:  p-value and confidence interval. 

If the p-value is .05 or less, the findings are considered statistically significant - not due to chance.

The confidence interval (CI) shows the level of confidence that the study outcome predicts the result in a larger population, expressed as a range.  The wider the range, the less confidence we have that the results of the study predicts outcomes in the real world.
  

Measures of statistical significance	Value or range  that  indicates statistical significance
p-value  threshold probability value that tells you if outcome is due to chance	.05 or less .01 is very good .05 is on threshold (borderline) .08 is not statistically significant
95% confidence interval (were the study repeated multiple times, it would contain the true effect 95% of the time)  - a range of expected results.	71% (95% CI: 42-92%) 83% (95% CI: 63-95%) 94% (95% CI: 63-97%) In the last example, we might say that we are 95% confident that the response rate is between 63 and 97%.   The wider the confidence interval the lower the confidence.

 Also see:

Absolute risk / Life time risk

The risk of developing a disease over a period of time. We all have absolute risks of developing various diseases such as heart disease, cancer, stroke, etc. The same absolute risk can be expressed in different ways. For example, you have a 1 in 50 risk of developing a lymphoma in your life. This can be expressed as a 2% risk, or a 0.02 risk.

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Types of Clinical Data (most reliable first)

Randomized controlled clinical trials: (Provides strongest evidence of clinical benefit)
 
Participants are assigned randomly (by chance instead of by investigator selectioni) to separate groups (arms) for the comparison of different treatments -- usually a standard and an investigational treatment. Patient informed consent is required. Neither the investigators nor the patient choose the group in which participants will be placed. 
 
Using chance to assign people to treatment arms helps to avoid selection bias -- putting pts in better health in the investigational arm, for example. It also helps to ensure that the groups will be similar and that the treatments they receive can be compared objectively. 

Randomized trials can be "double-blinded" or "non-blinded." In double-blind studies, neither the investigator nor the participants are informed of which arm the participants have been assigned to. This also reduces  bias and improves confidence in the findings.

NOTE: Systematic reviews that evaluate the outcomes in many trials, including randomized trials, may be the best source of evidence to guide clinical practice.
 

Nonrandomized controlled clinical trials

Participants are assigned to a treatment group based on criteria determined by the investigators, such as prognostic indicators, and disease type. This study design makes it possible for investigator bias to influence the findings, and therefore there is less confidence that the group receiving the treatment under study and the control group are comparable.

Case series (observational studies): 

Case series are studies (usually retrospective) that describe outcomes, such as responses, time to progression, etc.) from patients who received the treatment under investigation.  

These provide weaker evidence than do experimental studies because of the potential for biases such as, but not limited to, who is observed and what outcomes the observer is looking for, unknown association between factors and outcomes -- such as not accounting for other reasons that could explain the observed result. 
 
The value of these types of studies (e.g., case series, ecologic, case-control, cohort) is that they provide preliminary evidence that can be used as the basis for hypotheses testing in stronger experimental studies, such as randomized controlled trials. Consider the recent HRT report finding that using estrogens increases the risk of heart disease and cancers. The hypothesis that it might reduce these risks was based on observations that were proven to be incorrect. 

About press releases, and the reports you don't see
 
Protocols, ethical principles, and a desire to maintain credibility are beneficial forces that encourage responsible public reporting of drug development research and clinical trial outcomes. 

But consider that an easy way to put a positive spin on a company's drug development project is to selectively report on favorable outcomes, and to keep less than stellar results from being released at all.  

Ask: How is response to treatment being defined?  How were the patients selected?  How many patients were tested?  What was the control?  Has the finding been replicated by an independent group?  Have all the study outcomes been reported?  Is this an interim report, or a report on all -  predetermined number of participants?