Phase III trials tend to be much longer....
Phase III Clinical Trials
The following excerpt is taken from Chapter 2 of Cancer Clinical
Trials: Experimental Treatments & How They Can Help You by Robert
Finn, copyright 1999 by O'Reilly & Associates, Inc. For book
orders/information, call (800) 998-9938. Permission is granted to
print and distribute this excerpt for noncommercial use as long as the
above source is included. The information in this article is meant to
educate and should not be used as an alternative for professional
The most important thing to know about Phase III trials is that they are intended to see whether a new treatment is any better than the current standard treatments by making direct comparisons with those treatments. Sometimes there are two standard treatments for a certain type of cancer, and a Phase III trial is conducted to decide treatment is better. A treatment may be better if more patients go into remission, or if they stay in remission for a longer time, or if they suffer fewer side effects, compared to current treatments.
While the goal in Phase II trials is to find a relatively homogeneous group of patients, in Phase III investigators are looking for a more widely representative sample of the population. They will attempt to enroll hundreds or thousands of participants, preferably from all walks of life. As a consequence, inclusion and exclusion criteria may be less strict than in Phase II trials. Measurable disease, for example, is usually not required. Since many Phase III trials are multicenter trials, patients can be seen at medical centers in many parts of the country, so travel may be less of a burden.
On the other hand, investigators will generally be looking for patients who are newly diagnosed, and who have not yet received treatment for their cancer. Patients who have already received the standard or an experimental treatment may be excluded from Phase III trials.
Phase III trials tend to be much longer than Phase I and II trials, since the investigators are often interested in keeping track of how well the participants do years into the future.
Most Phase III trials are randomized. In a simple Phase III trial patients will be randomly assigned to receive the experimental treatment or the best available standard treatment. Often, however, the trial design may be more complex. Sometimes there may be two or more versions of the experimental treatment for comparison to two or more versions of standard treatments. For that reason it's very important for people considering Phase III trials to examine the trial's informed consent and protocol carefully to determine what chance one has of receiving experimental treatment.
Phase III trials are sometimes conducted in single- or double-blind fashion. As previously discussed, blinding is often pointless in cancer clinical trials; nevertheless investigators conduct blinded studies whenever possible.
Larry Sands (not his real name) had a typical Phase III experience soon after he was diagnosed with prostate cancer at the age of 45:
I was having some obstructive urinary problems. I'm a physician's assistant, and at my age I didn't think it was anything more serious than benign prostatic hypertrophy. My doctor drew blood for a PSA [prostate specific antigen] test, and it came back at 45, which is pretty high. Assuming that it was prostatitis, I took antibiotics for a month, but it rose to 47.
Larry's urologist diagnosed his problem as a moderately aggressive adenocarcinoma, and recommended a radical prostatectomy. But when the surgeon went in, he discovered that the cancer had spread to Larry's lymph nodes, so he didn't remove the prostate.
When he woke me up he told me that the cancer had already spread, that I had three to five years to live, and that I should go home and come back to see him in three months. I didn't think that was real logical, considering my age. I wanted to pursue treatment more aggressively. I looked for a clinical trial because there was no approved therapy for my cancer, at least until I got into bone pain.
During the course of the trial Larry's PSA dropped to undetectable levels, and stayed there for almost two years. However, his PSA recently started rising again, and Larry was diagnosed with a rare sarcoma of the prostate. Despite this setback, Larry does not regret participating in the clinical trial.
I went to my local oncologist, and she had a list of clinical trials. I went to the M. D. Anderson Cancer Center, which wasn't far from where I lived. They looked at my pathology slides and randomized me into a Phase III clinical trial.
One group received a relatively complex regimen of chemotherapy, and the other group just got watchful waiting and standard hormonal therapy, since there was no standard chemotherapy for the type of cancer I had. Fortunately I was randomized into the chemotherapy group. If I had been randomized into the other group, I would have found another protocol. I wasn't willing to sit and wait and do nothing.
I think it worked. The treatment may or may not have converted this adenocarcinoma into a sarcoma. The sarcoma may have been there to start with. There's just no way to tell. But sarcoma does have standard chemo protocols, and I just finished a round of chemotherapy.
Advantages of Phase III trials
Following are some of the advantages of participating in a Phase III clinical trial:
- It's a chance to receive a treatment that may be better than anything else out there a year or two before it hits the market.
- Treatments in Phase III trials have passed Phase I toxicity testing, and Phase II testing has proven them to be at least somewhat effective.
- Although you may be randomized to one of the standard treatment arms, the Data Safety and Monitoring Board will switch you to the experimental treatment during the course of the trial if it turns out to be significantly more effective.
- Similarly, if the experimental treatment proves to be less effective, patients in that arm of the study will be switched to the standard treatment.
- Inclusion and exclusion criteria for Phase III trials are generally less strict than in earlier phases. Measurable disease is often not a requirement.
- Since Phase III trials are generally multicenter trials, you may have to travel a shorter distance for treatments.
- Even if the treatment does not work for you personally, you may take comfort in knowing that your participation in the trial will help other cancer patients down the road, and it will also help the advancement of medical science.
Disadvantages of Phase III trials
Some of the disadvantages of participating in a Phase III clinical trial are:
- Many people do not wish to take the chance of being randomized into a standard treatment arm, and, in the case of blinded trials, many people do not like being kept in the dark about which treatment they're receiving.
- Even if one is randomized into the experimental arm of the study, the experimental treatment may be no better than the standard treatment, and it may be worse.
- Phase III is the first time the treatment is being given to a large and diverse group of patients. Adverse side effects that were not seen in earlier phases are likely to show up in Phase III.
- Phase III trials are often reserved for newly diagnosed patients who have not previously received treatment.
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