Unfortunately, volunteers who participate in these trials may not always have the right reasons for signing up. For instance, with the recession still taking its toll on the labor market, research clinics have reported anecdotal evidence about a "definite uptick in the number of patients," as ABC15.com reports, possibly as healthy people seek ways to earn a few extra bucks.

A quick internet search reveals many services, such as BioTrax and Paid Clinical Trials, that provide information for interested individuals and even more blogs and articles on the matter. Some people actually become professional guinea pigs, claiming that at $3,000-$6,000 ($100 to 300 a day) for each study, they can earn between $20,000 and $35,000 a year. It quickly becomes clear that it's a problem if individuals volunteer for trials not for the advancement of medical research but because of financial motivation or desperation. That's doubly so when volunteers don't appreciate the risks involved.

The Pfizer study, which is using lung-cancer patients, demonstrates the potential risks. The drugmaker puts it well on its site, saying "Pfizer recognizes that compensation to human research subjects should be structured so that subjects are not unduly influenced by such offers of compensation."

The U.S. Food & Drug Administration strictly regulates all clinical studies so that potential subjects are well informed of all events, including possible side effects, that may occur in a particular study, before the trial and during it. This is done through informed consent, which is the process of learning the key facts about a clinical trial before deciding whether or not to participate. It's also a continuing process throughout the study to provide information for participants. Doctors and nurses involved in the trial explain the details of the study to participants, and translation assistance can be provided if English isn't a participant's native language.

Then the research team provides an informed consent document, which describes the study participants' rights and includes details about the study, such as its purpose, duration, required procedures and key contacts. Risks and potential benefits are also explained there. Only when everything is clear should participants make the decision to sign up or not -- regardless of any financial payment. Informed consent is not a contract, and the participant may withdraw from the trial at any time. This is meant to keep health risks to a minimum.

In addition to pharmaceutical companies, clinical trials are also conducted by hospitals, universities and clinics -- often in collaboration. And such human trials are actually only a part of the research that goes into developing a new treatment. When a drug is developed, it first undergoes pre-clinical trials, including cell and animal studies. Then a request to study the drug in humans must be filed with the FDA. Only after approval is granted can the clinical trial phases begin.

These trials have several official Phases. In Phase 0, low drug doses are tested. Phase I tests the drug's safety in a small number of people (15 to 50). Phase II expands the trial to a larger group of 25 to 100 patients to test the treatment's efficiency. And Phase III, which uses a still-larger group, compares the safety and effectiveness of the new treatment against the current standard treatment. Lastly, Phase IV is a follow-up study after the drug has been approved and marketed to see what more can be learned about it.

The importance of clinical trials and participation in them cannot be emphasized enough. For example, while the Pfizer halt is a blow to the largest drugmaker in the world, the blow to patients is bigger because lung cancer is the leading cause of cancer deaths in the U.S. But, as Shari Roan of the Los Angeles Times wrote a few months back, it seems like Americans actually are unwilling to participate in clinical trials, "something which has been a serious drag on medical research."

One problem is that sometimes, as in the Pfizer lung-cancer study, safety issues crop up that should have been addressed in earlier phases. So, it's no wonder volunteers are hesitant. Researchers "acknowledge that some trials have been poorly conducted, risking patient health and dimming the public's view of medical research," Roan writes. In addition, information on how clinical trials are conducted is often poor, and more needs to be done to educate patients and make it easier to enroll safely in trials.

ClinicalTrials.gov, the National Cancer Institute and TrialCheck of the Coalition for Cancer are good places to start searching for clinical trials in general and cancer research studies in particular. The American Cancer Society also explains exactly the process and the importance of clinical trials. As in any risky endeavor, prudence is essential for drug-trial participants. When the decision to go ahead is made with full information and for the right motivation, however, the rewards are extremely compelling.